Thread: Join for the parent table will not leverage the index scan

Join for the parent table will not leverage the index scan

From

Shrikant Bhende

Date:

13 August 2021, 12:23:39

We have two tables, both have ~36 partitions.
This is my first query, which attempts to join the parent tables on the columns that have been used to create multi-column indexes for all partitions (multi-column indexes defined on session_id, detail_id in that order):

PostgreSQL version : 10
-- query

explain

select * from dm_ci360.page_details pd
inner join dm_ci360.page_details_ext pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)

where pd.session_dt >= now()::date-2;

-- plan

Hash Join (cost=36927955.75..100106605.07 rows=11 width=8355)

Hash Cond: (((pd.session_id)::text = (pde.session_id)::text) AND ((pd.detail_id)::text = (pde.detail_id)::text))

-> Append (cost=1297.33..571870.20 rows=630535 width=8130)

-> Bitmap Heap Scan on page_details_null pd (cost=1297.33..240207.85 rows=69259 width=8220)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_null_session_dt_idx (cost=0.00..1280.02 rows=69259 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m3_session_dt_idx on page_details_m3 pd_1 (cost=0.44..4.71 rows=1 width=8216)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m2_session_dt_idx on page_details_m2 pd_2 (cost=0.43..102.79 rows=621 width=8253)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m1_session_dt_idx on page_details_m1 pd_3 (cost=0.44..4.55 rows=1 width=8281)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd_4 (cost=0.57..51622.53 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Heap Scan on page_details_31 pd_5 (cost=982.61..194857.98 rows=52391 width=7721)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_31_session_dt_idx1 (cost=0.00..969.51 rows=52391 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_49_session_dt_idx on page_details_49 pd_6 (cost=0.45..10991.08 rows=50039 width=7721)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_52_session_dt_idx on page_details_52 pd_7 (cost=0.44..2337.94 rows=10222 width=8297)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_59_session_dt_idx on page_details_59 pd_8 (cost=0.57..24790.17 rows=50148 width=8276)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_60_session_dt_idx on page_details_60 pd_9 (cost=0.44..7292.41 rows=4259 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_61_session_dt_idx on page_details_61 pd_10 (cost=0.43..309.10 rows=704 width=8182)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_63_session_dt_idx on page_details_63 pd_11 (cost=0.43..13.20 rows=25 width=8250)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_64_session_dt_idx on page_details_64 pd_12 (cost=0.44..5.41 rows=1 width=8314)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_66_session_dt_idx on page_details_66 pd_13 (cost=0.42..4.49 rows=1 width=8277)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_67_session_dt_idx on page_details_67 pd_14 (cost=0.42..58.62 rows=325 width=8227)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_68_session_dt_idx on page_details_68 pd_15 (cost=0.42..35.20 rows=111 width=8259)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_78_session_dt_idx on page_details_78 pd_16 (cost=0.44..1738.10 rows=4608 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_98_session_dt_idx on page_details_98 pd_17 (cost=0.44..2157.31 rows=7136 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_101_session_dt_idx on page_details_101 pd_18 (cost=0.44..2956.03 rows=9241 width=8205)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_130_session_dt_idx on page_details_130 pd_19 (cost=0.44..1683.53 rows=19656 width=8199)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m100_session_dt_idx on page_details_m100 pd_20 (cost=0.43..4.96 rows=1 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m4_session_dt_idx on page_details_m4 pd_21 (cost=0.43..659.89 rows=6097 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_134_session_dt_idx on page_details_134 pd_22 (cost=0.45..4666.25 rows=50409 width=8176)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_58_session_dt_idx on page_details_58 pd_23 (cost=0.43..7.05 rows=1 width=8362)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_69_session_dt_idx on page_details_69 pd_24 (cost=0.43..125.03 rows=348 width=8268)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_100_session_dt_idx on page_details_100 pd_25 (cost=0.43..381.13 rows=466 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_114_session_dt_idx on page_details_114 pd_26 (cost=0.43..7.80 rows=1 width=8183)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m5_session_dt_idx on page_details_m5 pd_27 (cost=0.57..4505.18 rows=50872 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_32_session_dt_idx on page_details_32 pd_28 (cost=0.43..8.44 rows=1 width=8807)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_23_session_dt_idx on page_details_23 pd_29 (cost=0.29..7.47 rows=1 width=9327)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m6_session_dt_idx on page_details_m6 pd_30 (cost=0.44..769.32 rows=7135 width=7814)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m7_session_dt_idx on page_details_m7 pd_31 (cost=0.44..11400.50 rows=14694 width=8203)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m8_session_dt_idx on page_details_m8 pd_32 (cost=0.44..6568.86 rows=8045 width=8200)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_144_session_dt_idx on page_details_144 pd_33 (cost=0.29..21.16 rows=162 width=8189)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_143_session_dt_idx on page_details_143 pd_34 (cost=0.43..1477.00 rows=16135 width=8197)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_145_session_dt_idx on page_details_145 pd_35 (cost=0.29..87.17 rows=844 width=8226)

Index Cond: (session_dt >= ((now())::date - 2))

-> Hash (cost=16117516.77..16117516.77 rows=449927377 width=226)

-> Append (cost=0.00..16117516.77 rows=449927377 width=226)

-> Seq Scan on page_details_ext_null pde (cost=0.00..1467668.52 rows=40845752 width=226)

-> Seq Scan on page_details_ext_m3 pde_1 (cost=0.00..347732.32 rows=9980132 width=226)

-> Seq Scan on page_details_ext_m2 pde_2 (cost=0.00..26146.27 rows=715527 width=226)

-> Seq Scan on page_details_ext_m1 pde_3 (cost=0.00..180093.08 rows=4793908 width=226)

-> Seq Scan on page_details_ext_5 pde_4 (cost=0.00..3056150.08 rows=82652608 width=226)

-> Seq Scan on page_details_ext_31 pde_5 (cost=0.00..4177416.08 rows=124953208 width=226)

-> Seq Scan on page_details_ext_49 pde_6 (cost=0.00..1034364.84 rows=28538484 width=226)

-> Seq Scan on page_details_ext_52 pde_7 (cost=0.00..575529.72 rows=16018272 width=226)

-> Seq Scan on page_details_ext_59 pde_8 (cost=0.00..1226617.78 rows=33054378 width=226)

-> Seq Scan on page_details_ext_60 pde_9 (cost=0.00..206925.60 rows=5920260 width=226)

-> Seq Scan on page_details_ext_61 pde_10 (cost=0.00..10599.63 rows=296463 width=226)

-> Seq Scan on page_details_ext_63 pde_11 (cost=0.00..32993.45 rows=898145 width=226)

-> Seq Scan on page_details_ext_64 pde_12 (cost=0.00..211220.00 rows=6212500 width=226)

-> Seq Scan on page_details_ext_66 pde_13 (cost=0.00..4888.44 rows=127544 width=226)

-> Seq Scan on page_details_ext_67 pde_14 (cost=0.00..5121.02 rows=135402 width=226)

-> Seq Scan on page_details_ext_68 pde_15 (cost=0.00..4284.18 rows=116218 width=226)

-> Seq Scan on page_details_ext_78 pde_16 (cost=0.00..135663.64 rows=3705564 width=226)

-> Seq Scan on page_details_ext_98 pde_17 (cost=0.00..232421.44 rows=6556944 width=226)

-> Seq Scan on page_details_ext_101 pde_18 (cost=0.00..189844.81 rows=5231481 width=226)

-> Seq Scan on page_details_ext_130 pde_19 (cost=0.00..318011.40 rows=8558640 width=226)

-> Seq Scan on page_details_ext_m100 pde_20 (cost=0.00..4914.04 rows=143504 width=226)

-> Seq Scan on page_details_ext_m4 pde_21 (cost=0.00..75878.68 rows=1994468 width=226)

-> Seq Scan on page_details_ext_134 pde_22 (cost=0.00..724264.36 rows=19192136 width=226)

-> Seq Scan on page_details_ext_58 pde_23 (cost=0.00..12171.94 rows=361394 width=331)

-> Seq Scan on page_details_ext_69 pde_24 (cost=0.00..6464.95 rows=173295 width=226)

-> Seq Scan on page_details_ext_100 pde_25 (cost=0.00..9217.39 rows=255239 width=226)

-> Seq Scan on page_details_ext_114 pde_26 (cost=0.00..11702.69 rows=358469 width=226)

-> Seq Scan on page_details_ext_m5 pde_27 (cost=0.00..1274434.84 rows=33330284 width=226)

-> Seq Scan on page_details_ext_23 pde_28 (cost=0.00..822.03 rows=25503 width=378)

-> Seq Scan on page_details_ext_32 pde_29 (cost=0.00..7011.56 rows=217756 width=378)

-> Seq Scan on page_details_ext_m6 pde_30 (cost=0.00..177039.58 rows=4616658 width=226)

-> Seq Scan on page_details_ext_m7 pde_31 (cost=0.00..188264.43 rows=5143643 width=226)

-> Seq Scan on page_details_ext_m8 pde_32 (cost=0.00..139185.56 rows=3799056 width=226)

-> Seq Scan on page_details_ext_144 pde_33 (cost=0.00..687.46 rows=16246 width=226)

-> Seq Scan on page_details_ext_143 pde_34 (cost=0.00..41053.82 rows=971482 width=226)

-> Seq Scan on page_details_ext_145 pde_35 (cost=0.00..711.14 rows=16814 width=226)

The only place an index scan is used is to filter down page_details. In my second query,
when explicitly joining single partitions an index scan is used to perform filtering, and the join as well:

--query

explain

select * from dm_ci360.page_details_5 pd
inner join dm_ci360.page_details_ext_5 pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)

where pd.session_dt >= now()::date-2;

--plan

Nested Loop (cost=1.27..1685980.38 rows=1 width=8428)

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd (cost=0.57..51267.67 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_ext_5_session_id_detail_id_idx on page_details_ext_5 pde (cost=0.69..8.31 rows=1 width=226)

Index Cond: (((session_id)::text = (pd.session_id)::text) AND ((detail_id)::text = (pd.detail_id)::text))

I just cannot figure out why the join for the parent table will not leverage the index,
but the join for a single partition will. We are running on Postgres 10, and the row counts for the tables can be found below:

Row Count
page_details -> ~413M
page_details_ext -> ~450M

Table DDL

-- page_details

CREATE TABLE dm_ci360.page_details (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    visit_id varchar(32) NULL,
    window_size_txt varchar(20) NULL,
    session_dt date NULL,
    page_url_txt varchar(1332) NULL,
    domain_nm varchar(165) NULL,
    bytes_sent_cnt int4 NULL,
    page_load_sec_cnt int8 NULL,
    page_complete_sec_cnt int8 NULL,
    protocol_nm varchar(8) NULL,
    page_desc varchar(1332) NULL,
    class1_id varchar(650) NULL,
    class2_id varchar(650) NULL,
    class3_id varchar(650) NULL,
    class4_id varchar(650) NULL,
    class5_id varchar(650) NULL,
    class6_id varchar(650) NULL,
    class7_id varchar(650) NULL,
    class8_id varchar(650) NULL,
    class9_id varchar(650) NULL,
    class10_id varchar(650) NULL,
    class11_id varchar(650) NULL,
    class12_id varchar(650) NULL,
    class13_id varchar(650) NULL,
    class14_id varchar(650) NULL,
    class15_id varchar(650) NULL,
    url_domain varchar(215) NULL,
    identity_id varchar(36) NULL,
    detail_dttm timestamp NULL,
    detail_dttm_tz timestamp NULL,
    load_dttm timestamp NULL,
    session_dt_tz date NULL,
    detail_id_hex varchar(32) NULL,
    visit_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_100 PARTITION OF dm_ci360.page_details FOR VALUES IN (100);

CREATE INDEX page_details_100_detail_dttm_idx ON dm_ci360.page_details_100 USING btree (detail_dttm)
CREATE INDEX page_details_100_identity_id_idx ON dm_ci360.page_details_100 USING btree (identity_id)
CREATE INDEX page_details_100_session_dt_idx ON dm_ci360.page_details_100 USING btree (session_dt)
CREATE INDEX page_details_100_session_id_detail_id_idx ON dm_ci360.page_details_100 USING btree (session_id, detail_id)

-- page_details_ext

CREATE TABLE dm_ci360.page_details_ext (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    active_sec_spent_on_page_cnt int4 NULL,
    seconds_spent_on_page_cnt int4 NULL,
    load_dttm timestamp NULL,
    detail_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_ext_100 PARTITION OF dm_ci360.page_details_ext FOR VALUES IN (100);

CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)

CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)

Thanks

Re: Join for the parent table will not leverage the index scan

From

Vijaykumar Jain

Date:

13 August 2021, 15:50:06

On Fri, 13 Aug 2021 at 17:54, Shrikant Bhende <shrikantpostgresql@gmail.com> wrote:

The only place an index scan is used is to filter down page_details. In my second query,
when explicitly joining single partitions an index scan is used to perform filtering, and the join as well:

can you share the results of explain via New explain | explain.depesz.com

explain analyze <query>

set enable_seqscan TO off;

explain analyze <query>

maybe the planner seems to find seq scans faster than index scans.

The plan used by the optimizer should help understand the decision.

Also, I assume the tables were analyzed too.

If not, please run analyze on the tables.

also what do you see with enable_partitionwise_join enabled

set enable_partitionwise_join to on;

explain analyze <query>

set enable_seqscan TO off;

explain analyze <query>

Thanks,

Vijay

Mumbai, India

Re: Join for the parent table will not leverage the index scan

From

Shrikant Bhende

Date:

15 August 2021, 08:21:40

Any help on this would be really helpful.

On Fri, 13 Aug, 2021, 5:53 pm Shrikant Bhende, <shrikantpostgresql@gmail.com> wrote:

We have two tables, both have ~36 partitions.
This is my first query, which attempts to join the parent tables on the columns that have been used to create multi-column indexes for all partitions (multi-column indexes defined on session_id, detail_id in that order):

PostgreSQL version : 10
-- query

explain

select * from dm_ci360.page_details pd
inner join dm_ci360.page_details_ext pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)
where pd.session_dt >= now()::date-2;

-- plan

Hash Join (cost=36927955.75..100106605.07 rows=11 width=8355)

Hash Cond: (((pd.session_id)::text = (pde.session_id)::text) AND ((pd.detail_id)::text = (pde.detail_id)::text))

-> Append (cost=1297.33..571870.20 rows=630535 width=8130)

-> Bitmap Heap Scan on page_details_null pd (cost=1297.33..240207.85 rows=69259 width=8220)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_null_session_dt_idx (cost=0.00..1280.02 rows=69259 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m3_session_dt_idx on page_details_m3 pd_1 (cost=0.44..4.71 rows=1 width=8216)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m2_session_dt_idx on page_details_m2 pd_2 (cost=0.43..102.79 rows=621 width=8253)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m1_session_dt_idx on page_details_m1 pd_3 (cost=0.44..4.55 rows=1 width=8281)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd_4 (cost=0.57..51622.53 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Heap Scan on page_details_31 pd_5 (cost=982.61..194857.98 rows=52391 width=7721)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_31_session_dt_idx1 (cost=0.00..969.51 rows=52391 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_49_session_dt_idx on page_details_49 pd_6 (cost=0.45..10991.08 rows=50039 width=7721)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_52_session_dt_idx on page_details_52 pd_7 (cost=0.44..2337.94 rows=10222 width=8297)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_59_session_dt_idx on page_details_59 pd_8 (cost=0.57..24790.17 rows=50148 width=8276)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_60_session_dt_idx on page_details_60 pd_9 (cost=0.44..7292.41 rows=4259 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_61_session_dt_idx on page_details_61 pd_10 (cost=0.43..309.10 rows=704 width=8182)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_63_session_dt_idx on page_details_63 pd_11 (cost=0.43..13.20 rows=25 width=8250)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_64_session_dt_idx on page_details_64 pd_12 (cost=0.44..5.41 rows=1 width=8314)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_66_session_dt_idx on page_details_66 pd_13 (cost=0.42..4.49 rows=1 width=8277)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_67_session_dt_idx on page_details_67 pd_14 (cost=0.42..58.62 rows=325 width=8227)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_68_session_dt_idx on page_details_68 pd_15 (cost=0.42..35.20 rows=111 width=8259)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_78_session_dt_idx on page_details_78 pd_16 (cost=0.44..1738.10 rows=4608 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_98_session_dt_idx on page_details_98 pd_17 (cost=0.44..2157.31 rows=7136 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_101_session_dt_idx on page_details_101 pd_18 (cost=0.44..2956.03 rows=9241 width=8205)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_130_session_dt_idx on page_details_130 pd_19 (cost=0.44..1683.53 rows=19656 width=8199)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m100_session_dt_idx on page_details_m100 pd_20 (cost=0.43..4.96 rows=1 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m4_session_dt_idx on page_details_m4 pd_21 (cost=0.43..659.89 rows=6097 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_134_session_dt_idx on page_details_134 pd_22 (cost=0.45..4666.25 rows=50409 width=8176)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_58_session_dt_idx on page_details_58 pd_23 (cost=0.43..7.05 rows=1 width=8362)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_69_session_dt_idx on page_details_69 pd_24 (cost=0.43..125.03 rows=348 width=8268)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_100_session_dt_idx on page_details_100 pd_25 (cost=0.43..381.13 rows=466 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_114_session_dt_idx on page_details_114 pd_26 (cost=0.43..7.80 rows=1 width=8183)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m5_session_dt_idx on page_details_m5 pd_27 (cost=0.57..4505.18 rows=50872 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_32_session_dt_idx on page_details_32 pd_28 (cost=0.43..8.44 rows=1 width=8807)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_23_session_dt_idx on page_details_23 pd_29 (cost=0.29..7.47 rows=1 width=9327)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m6_session_dt_idx on page_details_m6 pd_30 (cost=0.44..769.32 rows=7135 width=7814)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m7_session_dt_idx on page_details_m7 pd_31 (cost=0.44..11400.50 rows=14694 width=8203)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m8_session_dt_idx on page_details_m8 pd_32 (cost=0.44..6568.86 rows=8045 width=8200)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_144_session_dt_idx on page_details_144 pd_33 (cost=0.29..21.16 rows=162 width=8189)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_143_session_dt_idx on page_details_143 pd_34 (cost=0.43..1477.00 rows=16135 width=8197)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_145_session_dt_idx on page_details_145 pd_35 (cost=0.29..87.17 rows=844 width=8226)

Index Cond: (session_dt >= ((now())::date - 2))

-> Hash (cost=16117516.77..16117516.77 rows=449927377 width=226)

-> Append (cost=0.00..16117516.77 rows=449927377 width=226)

-> Seq Scan on page_details_ext_null pde (cost=0.00..1467668.52 rows=40845752 width=226)

-> Seq Scan on page_details_ext_m3 pde_1 (cost=0.00..347732.32 rows=9980132 width=226)

-> Seq Scan on page_details_ext_m2 pde_2 (cost=0.00..26146.27 rows=715527 width=226)

-> Seq Scan on page_details_ext_m1 pde_3 (cost=0.00..180093.08 rows=4793908 width=226)

-> Seq Scan on page_details_ext_5 pde_4 (cost=0.00..3056150.08 rows=82652608 width=226)

-> Seq Scan on page_details_ext_31 pde_5 (cost=0.00..4177416.08 rows=124953208 width=226)

-> Seq Scan on page_details_ext_49 pde_6 (cost=0.00..1034364.84 rows=28538484 width=226)

-> Seq Scan on page_details_ext_52 pde_7 (cost=0.00..575529.72 rows=16018272 width=226)

-> Seq Scan on page_details_ext_59 pde_8 (cost=0.00..1226617.78 rows=33054378 width=226)

-> Seq Scan on page_details_ext_60 pde_9 (cost=0.00..206925.60 rows=5920260 width=226)

-> Seq Scan on page_details_ext_61 pde_10 (cost=0.00..10599.63 rows=296463 width=226)

-> Seq Scan on page_details_ext_63 pde_11 (cost=0.00..32993.45 rows=898145 width=226)

-> Seq Scan on page_details_ext_64 pde_12 (cost=0.00..211220.00 rows=6212500 width=226)

-> Seq Scan on page_details_ext_66 pde_13 (cost=0.00..4888.44 rows=127544 width=226)

-> Seq Scan on page_details_ext_67 pde_14 (cost=0.00..5121.02 rows=135402 width=226)

-> Seq Scan on page_details_ext_68 pde_15 (cost=0.00..4284.18 rows=116218 width=226)

-> Seq Scan on page_details_ext_78 pde_16 (cost=0.00..135663.64 rows=3705564 width=226)

-> Seq Scan on page_details_ext_98 pde_17 (cost=0.00..232421.44 rows=6556944 width=226)

-> Seq Scan on page_details_ext_101 pde_18 (cost=0.00..189844.81 rows=5231481 width=226)

-> Seq Scan on page_details_ext_130 pde_19 (cost=0.00..318011.40 rows=8558640 width=226)

-> Seq Scan on page_details_ext_m100 pde_20 (cost=0.00..4914.04 rows=143504 width=226)

-> Seq Scan on page_details_ext_m4 pde_21 (cost=0.00..75878.68 rows=1994468 width=226)

-> Seq Scan on page_details_ext_134 pde_22 (cost=0.00..724264.36 rows=19192136 width=226)

-> Seq Scan on page_details_ext_58 pde_23 (cost=0.00..12171.94 rows=361394 width=331)

-> Seq Scan on page_details_ext_69 pde_24 (cost=0.00..6464.95 rows=173295 width=226)

-> Seq Scan on page_details_ext_100 pde_25 (cost=0.00..9217.39 rows=255239 width=226)

-> Seq Scan on page_details_ext_114 pde_26 (cost=0.00..11702.69 rows=358469 width=226)

-> Seq Scan on page_details_ext_m5 pde_27 (cost=0.00..1274434.84 rows=33330284 width=226)

-> Seq Scan on page_details_ext_23 pde_28 (cost=0.00..822.03 rows=25503 width=378)

-> Seq Scan on page_details_ext_32 pde_29 (cost=0.00..7011.56 rows=217756 width=378)

-> Seq Scan on page_details_ext_m6 pde_30 (cost=0.00..177039.58 rows=4616658 width=226)

-> Seq Scan on page_details_ext_m7 pde_31 (cost=0.00..188264.43 rows=5143643 width=226)

-> Seq Scan on page_details_ext_m8 pde_32 (cost=0.00..139185.56 rows=3799056 width=226)

-> Seq Scan on page_details_ext_144 pde_33 (cost=0.00..687.46 rows=16246 width=226)

-> Seq Scan on page_details_ext_143 pde_34 (cost=0.00..41053.82 rows=971482 width=226)

-> Seq Scan on page_details_ext_145 pde_35 (cost=0.00..711.14 rows=16814 width=226)

The only place an index scan is used is to filter down page_details. In my second query,
when explicitly joining single partitions an index scan is used to perform filtering, and the join as well:

--query

explain

select * from dm_ci360.page_details_5 pd
inner join dm_ci360.page_details_ext_5 pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)
where pd.session_dt >= now()::date-2;

--plan

Nested Loop (cost=1.27..1685980.38 rows=1 width=8428)

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd (cost=0.57..51267.67 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_ext_5_session_id_detail_id_idx on page_details_ext_5 pde (cost=0.69..8.31 rows=1 width=226)

Index Cond: (((session_id)::text = (pd.session_id)::text) AND ((detail_id)::text = (pd.detail_id)::text))

I just cannot figure out why the join for the parent table will not leverage the index,
but the join for a single partition will. We are running on Postgres 10, and the row counts for the tables can be found below:

Row Count
page_details -> ~413M
page_details_ext -> ~450M

Table DDL
-- page_details

CREATE TABLE dm_ci360.page_details (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    visit_id varchar(32) NULL,
    window_size_txt varchar(20) NULL,
    session_dt date NULL,
    page_url_txt varchar(1332) NULL,
    domain_nm varchar(165) NULL,
    bytes_sent_cnt int4 NULL,
    page_load_sec_cnt int8 NULL,
    page_complete_sec_cnt int8 NULL,
    protocol_nm varchar(8) NULL,
    page_desc varchar(1332) NULL,
    class1_id varchar(650) NULL,
    class2_id varchar(650) NULL,
    class3_id varchar(650) NULL,
    class4_id varchar(650) NULL,
    class5_id varchar(650) NULL,
    class6_id varchar(650) NULL,
    class7_id varchar(650) NULL,
    class8_id varchar(650) NULL,
    class9_id varchar(650) NULL,
    class10_id varchar(650) NULL,
    class11_id varchar(650) NULL,
    class12_id varchar(650) NULL,
    class13_id varchar(650) NULL,
    class14_id varchar(650) NULL,
    class15_id varchar(650) NULL,
    url_domain varchar(215) NULL,
    identity_id varchar(36) NULL,
    detail_dttm timestamp NULL,
    detail_dttm_tz timestamp NULL,
    load_dttm timestamp NULL,
    session_dt_tz date NULL,
    detail_id_hex varchar(32) NULL,
    visit_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_100 PARTITION OF dm_ci360.page_details FOR VALUES IN (100);

CREATE INDEX page_details_100_detail_dttm_idx ON dm_ci360.page_details_100 USING btree (detail_dttm)
CREATE INDEX page_details_100_identity_id_idx ON dm_ci360.page_details_100 USING btree (identity_id)
CREATE INDEX page_details_100_session_dt_idx ON dm_ci360.page_details_100 USING btree (session_dt)
CREATE INDEX page_details_100_session_id_detail_id_idx ON dm_ci360.page_details_100 USING btree (session_id, detail_id)

-- page_details_ext

CREATE TABLE dm_ci360.page_details_ext (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    active_sec_spent_on_page_cnt int4 NULL,
    seconds_spent_on_page_cnt int4 NULL,
    load_dttm timestamp NULL,
    detail_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_ext_100 PARTITION OF dm_ci360.page_details_ext FOR VALUES IN (100);

CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)
CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)
Thanks

Re: Join for the parent table will not leverage the index scan

From

Ron

Date:

16 August 2021, 04:17:07

When were the tables last analyzed?

Also, the whole set of partitions must be scanned, since the tables are partitioned by a field other than what's in the JOIN and WHERE clauses.

On 8/13/21 7:23 AM, Shrikant Bhende wrote:

We have two tables, both have ~36 partitions.
This is my first query, which attempts to join the parent tables on the columns that have been used to create multi-column indexes for all partitions (multi-column indexes defined on session_id, detail_id in that order):

PostgreSQL version : 10
-- query

explain

select * from dm_ci360.page_details pd
inner join dm_ci360.page_details_ext pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)
where pd.session_dt >= now()::date-2;

-- plan

Hash Join (cost=36927955.75..100106605.07 rows=11 width=8355)

Hash Cond: (((pd.session_id)::text = (pde.session_id)::text) AND ((pd.detail_id)::text = (pde.detail_id)::text))

-> Append (cost=1297.33..571870.20 rows=630535 width=8130)

-> Bitmap Heap Scan on page_details_null pd (cost=1297.33..240207.85 rows=69259 width=8220)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_null_session_dt_idx (cost=0.00..1280.02 rows=69259 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m3_session_dt_idx on page_details_m3 pd_1 (cost=0.44..4.71 rows=1 width=8216)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m2_session_dt_idx on page_details_m2 pd_2 (cost=0.43..102.79 rows=621 width=8253)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m1_session_dt_idx on page_details_m1 pd_3 (cost=0.44..4.55 rows=1 width=8281)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd_4 (cost=0.57..51622.53 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Heap Scan on page_details_31 pd_5 (cost=982.61..194857.98 rows=52391 width=7721)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_31_session_dt_idx1 (cost=0.00..969.51 rows=52391 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_49_session_dt_idx on page_details_49 pd_6 (cost=0.45..10991.08 rows=50039 width=7721)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_52_session_dt_idx on page_details_52 pd_7 (cost=0.44..2337.94 rows=10222 width=8297)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_59_session_dt_idx on page_details_59 pd_8 (cost=0.57..24790.17 rows=50148 width=8276)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_60_session_dt_idx on page_details_60 pd_9 (cost=0.44..7292.41 rows=4259 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_61_session_dt_idx on page_details_61 pd_10 (cost=0.43..309.10 rows=704 width=8182)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_63_session_dt_idx on page_details_63 pd_11 (cost=0.43..13.20 rows=25 width=8250)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_64_session_dt_idx on page_details_64 pd_12 (cost=0.44..5.41 rows=1 width=8314)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_66_session_dt_idx on page_details_66 pd_13 (cost=0.42..4.49 rows=1 width=8277)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_67_session_dt_idx on page_details_67 pd_14 (cost=0.42..58.62 rows=325 width=8227)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_68_session_dt_idx on page_details_68 pd_15 (cost=0.42..35.20 rows=111 width=8259)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_78_session_dt_idx on page_details_78 pd_16 (cost=0.44..1738.10 rows=4608 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_98_session_dt_idx on page_details_98 pd_17 (cost=0.44..2157.31 rows=7136 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_101_session_dt_idx on page_details_101 pd_18 (cost=0.44..2956.03 rows=9241 width=8205)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_130_session_dt_idx on page_details_130 pd_19 (cost=0.44..1683.53 rows=19656 width=8199)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m100_session_dt_idx on page_details_m100 pd_20 (cost=0.43..4.96 rows=1 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m4_session_dt_idx on page_details_m4 pd_21 (cost=0.43..659.89 rows=6097 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_134_session_dt_idx on page_details_134 pd_22 (cost=0.45..4666.25 rows=50409 width=8176)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_58_session_dt_idx on page_details_58 pd_23 (cost=0.43..7.05 rows=1 width=8362)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_69_session_dt_idx on page_details_69 pd_24 (cost=0.43..125.03 rows=348 width=8268)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_100_session_dt_idx on page_details_100 pd_25 (cost=0.43..381.13 rows=466 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_114_session_dt_idx on page_details_114 pd_26 (cost=0.43..7.80 rows=1 width=8183)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m5_session_dt_idx on page_details_m5 pd_27 (cost=0.57..4505.18 rows=50872 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_32_session_dt_idx on page_details_32 pd_28 (cost=0.43..8.44 rows=1 width=8807)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_23_session_dt_idx on page_details_23 pd_29 (cost=0.29..7.47 rows=1 width=9327)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m6_session_dt_idx on page_details_m6 pd_30 (cost=0.44..769.32 rows=7135 width=7814)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m7_session_dt_idx on page_details_m7 pd_31 (cost=0.44..11400.50 rows=14694 width=8203)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m8_session_dt_idx on page_details_m8 pd_32 (cost=0.44..6568.86 rows=8045 width=8200)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_144_session_dt_idx on page_details_144 pd_33 (cost=0.29..21.16 rows=162 width=8189)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_143_session_dt_idx on page_details_143 pd_34 (cost=0.43..1477.00 rows=16135 width=8197)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_145_session_dt_idx on page_details_145 pd_35 (cost=0.29..87.17 rows=844 width=8226)

Index Cond: (session_dt >= ((now())::date - 2))

-> Hash (cost=16117516.77..16117516.77 rows=449927377 width=226)

-> Append (cost=0.00..16117516.77 rows=449927377 width=226)

-> Seq Scan on page_details_ext_null pde (cost=0.00..1467668.52 rows=40845752 width=226)

-> Seq Scan on page_details_ext_m3 pde_1 (cost=0.00..347732.32 rows=9980132 width=226)

-> Seq Scan on page_details_ext_m2 pde_2 (cost=0.00..26146.27 rows=715527 width=226)

-> Seq Scan on page_details_ext_m1 pde_3 (cost=0.00..180093.08 rows=4793908 width=226)

-> Seq Scan on page_details_ext_5 pde_4 (cost=0.00..3056150.08 rows=82652608 width=226)

-> Seq Scan on page_details_ext_31 pde_5 (cost=0.00..4177416.08 rows=124953208 width=226)

-> Seq Scan on page_details_ext_49 pde_6 (cost=0.00..1034364.84 rows=28538484 width=226)

-> Seq Scan on page_details_ext_52 pde_7 (cost=0.00..575529.72 rows=16018272 width=226)

-> Seq Scan on page_details_ext_59 pde_8 (cost=0.00..1226617.78 rows=33054378 width=226)

-> Seq Scan on page_details_ext_60 pde_9 (cost=0.00..206925.60 rows=5920260 width=226)

-> Seq Scan on page_details_ext_61 pde_10 (cost=0.00..10599.63 rows=296463 width=226)

-> Seq Scan on page_details_ext_63 pde_11 (cost=0.00..32993.45 rows=898145 width=226)

-> Seq Scan on page_details_ext_64 pde_12 (cost=0.00..211220.00 rows=6212500 width=226)

-> Seq Scan on page_details_ext_66 pde_13 (cost=0.00..4888.44 rows=127544 width=226)

-> Seq Scan on page_details_ext_67 pde_14 (cost=0.00..5121.02 rows=135402 width=226)

-> Seq Scan on page_details_ext_68 pde_15 (cost=0.00..4284.18 rows=116218 width=226)

-> Seq Scan on page_details_ext_78 pde_16 (cost=0.00..135663.64 rows=3705564 width=226)

-> Seq Scan on page_details_ext_98 pde_17 (cost=0.00..232421.44 rows=6556944 width=226)

-> Seq Scan on page_details_ext_101 pde_18 (cost=0.00..189844.81 rows=5231481 width=226)

-> Seq Scan on page_details_ext_130 pde_19 (cost=0.00..318011.40 rows=8558640 width=226)

-> Seq Scan on page_details_ext_m100 pde_20 (cost=0.00..4914.04 rows=143504 width=226)

-> Seq Scan on page_details_ext_m4 pde_21 (cost=0.00..75878.68 rows=1994468 width=226)

-> Seq Scan on page_details_ext_134 pde_22 (cost=0.00..724264.36 rows=19192136 width=226)

-> Seq Scan on page_details_ext_58 pde_23 (cost=0.00..12171.94 rows=361394 width=331)

-> Seq Scan on page_details_ext_69 pde_24 (cost=0.00..6464.95 rows=173295 width=226)

-> Seq Scan on page_details_ext_100 pde_25 (cost=0.00..9217.39 rows=255239 width=226)

-> Seq Scan on page_details_ext_114 pde_26 (cost=0.00..11702.69 rows=358469 width=226)

-> Seq Scan on page_details_ext_m5 pde_27 (cost=0.00..1274434.84 rows=33330284 width=226)

-> Seq Scan on page_details_ext_23 pde_28 (cost=0.00..822.03 rows=25503 width=378)

-> Seq Scan on page_details_ext_32 pde_29 (cost=0.00..7011.56 rows=217756 width=378)

-> Seq Scan on page_details_ext_m6 pde_30 (cost=0.00..177039.58 rows=4616658 width=226)

-> Seq Scan on page_details_ext_m7 pde_31 (cost=0.00..188264.43 rows=5143643 width=226)

-> Seq Scan on page_details_ext_m8 pde_32 (cost=0.00..139185.56 rows=3799056 width=226)

-> Seq Scan on page_details_ext_144 pde_33 (cost=0.00..687.46 rows=16246 width=226)

-> Seq Scan on page_details_ext_143 pde_34 (cost=0.00..41053.82 rows=971482 width=226)

-> Seq Scan on page_details_ext_145 pde_35 (cost=0.00..711.14 rows=16814 width=226)

The only place an index scan is used is to filter down page_details. In my second query,
when explicitly joining single partitions an index scan is used to perform filtering, and the join as well:

--query

explain

select * from dm_ci360.page_details_5 pd
inner join dm_ci360.page_details_ext_5 pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)
where pd.session_dt >= now()::date-2;

--plan

Nested Loop (cost=1.27..1685980.38 rows=1 width=8428)

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd (cost=0.57..51267.67 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_ext_5_session_id_detail_id_idx on page_details_ext_5 pde (cost=0.69..8.31 rows=1 width=226)

Index Cond: (((session_id)::text = (pd.session_id)::text) AND ((detail_id)::text = (pd.detail_id)::text))

I just cannot figure out why the join for the parent table will not leverage the index,
but the join for a single partition will. We are running on Postgres 10, and the row counts for the tables can be found below:

Row Count
page_details -> ~413M
page_details_ext -> ~450M

Table DDL
-- page_details

CREATE TABLE dm_ci360.page_details (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    visit_id varchar(32) NULL,
    window_size_txt varchar(20) NULL,
    session_dt date NULL,
    page_url_txt varchar(1332) NULL,
    domain_nm varchar(165) NULL,
    bytes_sent_cnt int4 NULL,
    page_load_sec_cnt int8 NULL,
    page_complete_sec_cnt int8 NULL,
    protocol_nm varchar(8) NULL,
    page_desc varchar(1332) NULL,
    class1_id varchar(650) NULL,
    class2_id varchar(650) NULL,
    class3_id varchar(650) NULL,
    class4_id varchar(650) NULL,
    class5_id varchar(650) NULL,
    class6_id varchar(650) NULL,
    class7_id varchar(650) NULL,
    class8_id varchar(650) NULL,
    class9_id varchar(650) NULL,
    class10_id varchar(650) NULL,
    class11_id varchar(650) NULL,
    class12_id varchar(650) NULL,
    class13_id varchar(650) NULL,
    class14_id varchar(650) NULL,
    class15_id varchar(650) NULL,
    url_domain varchar(215) NULL,
    identity_id varchar(36) NULL,
    detail_dttm timestamp NULL,
    detail_dttm_tz timestamp NULL,
    load_dttm timestamp NULL,
    session_dt_tz date NULL,
    detail_id_hex varchar(32) NULL,
    visit_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_100 PARTITION OF dm_ci360.page_details FOR VALUES IN (100);

CREATE INDEX page_details_100_detail_dttm_idx ON dm_ci360.page_details_100 USING btree (detail_dttm)
CREATE INDEX page_details_100_identity_id_idx ON dm_ci360.page_details_100 USING btree (identity_id)
CREATE INDEX page_details_100_session_dt_idx ON dm_ci360.page_details_100 USING btree (session_dt)
CREATE INDEX page_details_100_session_id_detail_id_idx ON dm_ci360.page_details_100 USING btree (session_id, detail_id)

-- page_details_ext

CREATE TABLE dm_ci360.page_details_ext (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    active_sec_spent_on_page_cnt int4 NULL,
    seconds_spent_on_page_cnt int4 NULL,
    load_dttm timestamp NULL,
    detail_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_ext_100 PARTITION OF dm_ci360.page_details_ext FOR VALUES IN (100);

CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)
CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)
Thanks

--
Angular momentum makes the world go 'round.

Re: Join for the parent table will not leverage the index scan

From

Shrikant Bhende

Date:

17 August 2021, 03:25:33

Hi Ron,

Thanks for the reply and clarification.

Tables are getting analyzed regularly also did analze today as well,

Below is the test case where I tried to use the partition key in join,

but still getting the same result.

explain
select *
from dm_ci360.page_details pd
left join dm_ci360.page_details_ext pde
    on (pd.detail_id = pde.detail_id
        and pd.client_id = pde.client_id);
    
    --
    
    "QUERY PLAN"
Gather  (cost=1328436468.62..1375694672.28 rows=421291719 width=8287)
  Workers Planned: 8
  ->  Merge Left Join  (cost=1328435468.62..1333564500.38 rows=52661465 width=8287)
        Merge Cond: (((pd.detail_id)::text = (pde.detail_id)::text) AND (pd.client_id = pde.client_id))
        ->  Sort  (cost=1045342980.27..1045489637.23 rows=58662783 width=8061)
"              Sort Key: pd.detail_id, pd.client_id"
              ->  Append  (cost=0.00..24208020.84 rows=58662783 width=8061)
                    ->  Parallel Seq Scan on page_details_null pd  (cost=0.00..2425406.85 rows=5120384 width=8220)
                    ->  Parallel Seq Scan on page_details_m3 pd_1  (cost=0.00..503325.67 rows=1484767 width=8216)
                    ->  Parallel Seq Scan on page_details_m2 pd_2  (cost=0.00..41493.07 rows=158208 width=8253)
                    ->  Parallel Seq Scan on page_details_m1 pd_3  (cost=0.00..298542.32 rows=718532 width=8281)
                    ->  Parallel Seq Scan on page_details_5 pd_4  (cost=0.00..4546231.40 rows=9936540 width=8202)
                    ->  Parallel Seq Scan on page_details_31 pd_5  (cost=0.00..5351785.68 rows=13473668 width=7721)
                    ->  Parallel Seq Scan on page_details_49 pd_6  (cost=0.00..1528222.35 rows=3763935 width=7721)
                    ->  Parallel Seq Scan on page_details_52 pd_7  (cost=0.00..1005739.96 rows=2113496 width=8297)
                    ->  Parallel Seq Scan on page_details_59 pd_8  (cost=0.00..2139754.44 rows=4577244 width=8276)
                    ->  Parallel Seq Scan on page_details_60 pd_9  (cost=0.00..316209.20 rows=846820 width=8263)
                    ->  Parallel Seq Scan on page_details_61 pd_10  (cost=0.00..14790.59 rows=85759 width=8182)
                    ->  Parallel Seq Scan on page_details_63 pd_11  (cost=0.00..52206.08 rows=204008 width=8250)
                    ->  Parallel Seq Scan on page_details_64 pd_12  (cost=0.00..358858.43 rows=904143 width=8314)
                    ->  Parallel Seq Scan on page_details_66 pd_13  (cost=0.00..8647.65 rows=50365 width=8277)
                    ->  Parallel Seq Scan on page_details_67 pd_14  (cost=0.00..8507.65 rows=54465 width=8227)
                    ->  Parallel Seq Scan on page_details_68 pd_15  (cost=0.00..7667.92 rows=47192 width=8259)
                    ->  Parallel Seq Scan on page_details_78 pd_16  (cost=0.00..227673.87 rows=698287 width=8263)
                    ->  Parallel Seq Scan on page_details_98 pd_17  (cost=0.00..342905.89 rows=975589 width=8225)
                    ->  Parallel Seq Scan on page_details_101 pd_18  (cost=0.00..277631.48 rows=815948 width=8205)
                    ->  Parallel Seq Scan on page_details_130 pd_19  (cost=0.00..489453.45 rows=1409344 width=8199)
                    ->  Parallel Seq Scan on page_details_m100 pd_20  (cost=0.00..8943.50 rows=62750 width=8225)
                    ->  Parallel Seq Scan on page_details_m4 pd_21  (cost=0.00..119599.55 rows=409355 width=8195)
                    ->  Parallel Seq Scan on page_details_134 pd_22  (cost=0.00..1078678.24 rows=2791724 width=8176)
                    ->  Parallel Seq Scan on page_details_58 pd_23  (cost=0.00..19107.17 rows=114617 width=8362)
                    ->  Parallel Seq Scan on page_details_69 pd_24  (cost=0.00..11774.27 rows=56027 width=8268)
                    ->  Parallel Seq Scan on page_details_100 pd_25  (cost=0.00..14765.61 rows=83161 width=8195)
                    ->  Parallel Seq Scan on page_details_114 pd_26  (cost=0.00..17953.55 rows=112155 width=8183)
                    ->  Parallel Seq Scan on page_details_m5 pd_27  (cost=0.00..2069930.14 rows=4803014 width=8225)
                    ->  Parallel Seq Scan on page_details_32 pd_28  (cost=0.00..9655.67 rows=90767 width=8807)
                    ->  Parallel Seq Scan on page_details_23 pd_29  (cost=0.00..1183.66 rows=14966 width=9327)
                    ->  Parallel Seq Scan on page_details_m6 pd_30  (cost=0.00..331066.68 rows=766068 width=7814)
                    ->  Parallel Seq Scan on page_details_m7 pd_31  (cost=0.00..276835.86 rows=820386 width=8203)
                    ->  Parallel Seq Scan on page_details_m8 pd_32  (cost=0.00..219677.99 rows=764299 width=8200)
                    ->  Parallel Seq Scan on page_details_144 pd_33  (cost=0.00..1243.71 rows=10671 width=8189)
                    ->  Parallel Seq Scan on page_details_143 pd_34  (cost=0.00..79279.91 rows=304892 width=8196)
                    ->  Parallel Seq Scan on page_details_145 pd_35  (cost=0.00..3271.37 rows=19237 width=8226)
        ->  Materialize  (cost=283092488.35..285385333.09 rows=458568949 width=226)
              ->  Sort  (cost=283092488.35..284238910.72 rows=458568949 width=226)
"                    Sort Key: pde.detail_id, pde.client_id"
                    ->  Append  (cost=0.00..16497547.49 rows=458568949 width=226)
                          ->  Seq Scan on page_details_ext_null pde  (cost=0.00..1524481.42 rows=42223842 width=226)
                          ->  Seq Scan on page_details_ext_m3 pde_1  (cost=0.00..347731.78 rows=9980078 width=226)
                          ->  Seq Scan on page_details_ext_m2 pde_2  (cost=0.00..26437.83 rows=721783 width=226)
                          ->  Seq Scan on page_details_ext_m1 pde_3  (cost=0.00..180092.12 rows=4793812 width=226)
                          ->  Seq Scan on page_details_ext_5 pde_4  (cost=0.00..3157905.57 rows=84945757 width=226)
                          ->  Seq Scan on page_details_ext_31 pde_5  (cost=0.00..4198600.83 rows=125384283 width=226)
                          ->  Seq Scan on page_details_ext_49 pde_6  (cost=0.00..1058695.45 rows=29083145 width=226)
                          ->  Seq Scan on page_details_ext_52 pde_7  (cost=0.00..582580.50 rows=16175450 width=226)
                          ->  Seq Scan on page_details_ext_59 pde_8  (cost=0.00..1276447.65 rows=34184965 width=226)
                          ->  Seq Scan on page_details_ext_60 pde_9  (cost=0.00..209865.67 rows=5987267 width=226)
                          ->  Seq Scan on page_details_ext_61 pde_10  (cost=0.00..10846.58 rows=301558 width=226)
                          ->  Seq Scan on page_details_ext_63 pde_11  (cost=0.00..32991.51 rows=897951 width=226)
                          ->  Seq Scan on page_details_ext_64 pde_12  (cost=0.00..211218.56 rows=6212356 width=226)
                          ->  Seq Scan on page_details_ext_66 pde_13  (cost=0.00..4888.06 rows=127506 width=226)
                          ->  Seq Scan on page_details_ext_67 pde_14  (cost=0.00..5320.29 rows=139829 width=226)
                          ->  Seq Scan on page_details_ext_68 pde_15  (cost=0.00..4519.19 rows=121219 width=226)
                          ->  Seq Scan on page_details_ext_78 pde_16  (cost=0.00..138728.11 rows=3774711 width=226)
                          ->  Seq Scan on page_details_ext_98 pde_17  (cost=0.00..235653.77 rows=6628477 width=226)
                          ->  Seq Scan on page_details_ext_101 pde_18  (cost=0.00..195898.44 rows=5365744 width=226)
                          ->  Seq Scan on page_details_ext_130 pde_19  (cost=0.00..327932.65 rows=8781965 width=226)
                          ->  Seq Scan on page_details_ext_m100 pde_20  (cost=0.00..4913.38 rows=143438 width=226)
                          ->  Seq Scan on page_details_ext_m4 pde_21  (cost=0.00..79001.77 rows=2065777 width=226)
                          ->  Seq Scan on page_details_ext_134 pde_22  (cost=0.00..757767.21 rows=19952321 width=226)
                          ->  Seq Scan on page_details_ext_58 pde_23  (cost=0.00..12171.64 rows=361364 width=331)
                          ->  Seq Scan on page_details_ext_69 pde_24  (cost=0.00..6617.58 rows=176558 width=226)
                          ->  Seq Scan on page_details_ext_100 pde_25  (cost=0.00..9531.93 rows=261993 width=226)
                          ->  Seq Scan on page_details_ext_114 pde_26  (cost=0.00..11702.72 rows=358372 width=226)
                          ->  Seq Scan on page_details_ext_m5 pde_27  (cost=0.00..1300373.49 rows=33923749 width=226)
                          ->  Seq Scan on page_details_ext_23 pde_28  (cost=0.00..819.39 rows=25239 width=378)
                          ->  Seq Scan on page_details_ext_32 pde_29  (cost=0.00..7009.04 rows=217504 width=378)
                          ->  Seq Scan on page_details_ext_m6 pde_30  (cost=0.00..181575.92 rows=4720692 width=226)
                          ->  Seq Scan on page_details_ext_m7 pde_31  (cost=0.00..196632.54 rows=5332554 width=226)
                          ->  Seq Scan on page_details_ext_m8 pde_32  (cost=0.00..142816.57 rows=3877857 width=226)
                          ->  Seq Scan on page_details_ext_144 pde_33  (cost=0.00..780.22 rows=18422 width=226)
                          ->  Seq Scan on page_details_ext_143 pde_34  (cost=0.00..53050.54 rows=1255354 width=226)
                          ->  Seq Scan on page_details_ext_145 pde_35  (cost=0.00..1947.57 rows=46057 width=226)

Thanks

On Mon, Aug 16, 2021 at 9:47 AM Ron <ronljohnsonjr@gmail.com> wrote:

When were the tables last analyzed?

Also, the whole set of partitions must be scanned, since the tables are partitioned by a field other than what's in the JOIN and WHERE clauses.

On 8/13/21 7:23 AM, Shrikant Bhende wrote:
We have two tables, both have ~36 partitions.
This is my first query, which attempts to join the parent tables on the columns that have been used to create multi-column indexes for all partitions (multi-column indexes defined on session_id, detail_id in that order):

PostgreSQL version : 10
-- query

explain

select * from dm_ci360.page_details pd
inner join dm_ci360.page_details_ext pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)
where pd.session_dt >= now()::date-2;

-- plan

Hash Join (cost=36927955.75..100106605.07 rows=11 width=8355)

Hash Cond: (((pd.session_id)::text = (pde.session_id)::text) AND ((pd.detail_id)::text = (pde.detail_id)::text))

-> Append (cost=1297.33..571870.20 rows=630535 width=8130)

-> Bitmap Heap Scan on page_details_null pd (cost=1297.33..240207.85 rows=69259 width=8220)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_null_session_dt_idx (cost=0.00..1280.02 rows=69259 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m3_session_dt_idx on page_details_m3 pd_1 (cost=0.44..4.71 rows=1 width=8216)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m2_session_dt_idx on page_details_m2 pd_2 (cost=0.43..102.79 rows=621 width=8253)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m1_session_dt_idx on page_details_m1 pd_3 (cost=0.44..4.55 rows=1 width=8281)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd_4 (cost=0.57..51622.53 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Heap Scan on page_details_31 pd_5 (cost=982.61..194857.98 rows=52391 width=7721)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_31_session_dt_idx1 (cost=0.00..969.51 rows=52391 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_49_session_dt_idx on page_details_49 pd_6 (cost=0.45..10991.08 rows=50039 width=7721)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_52_session_dt_idx on page_details_52 pd_7 (cost=0.44..2337.94 rows=10222 width=8297)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_59_session_dt_idx on page_details_59 pd_8 (cost=0.57..24790.17 rows=50148 width=8276)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_60_session_dt_idx on page_details_60 pd_9 (cost=0.44..7292.41 rows=4259 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_61_session_dt_idx on page_details_61 pd_10 (cost=0.43..309.10 rows=704 width=8182)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_63_session_dt_idx on page_details_63 pd_11 (cost=0.43..13.20 rows=25 width=8250)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_64_session_dt_idx on page_details_64 pd_12 (cost=0.44..5.41 rows=1 width=8314)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_66_session_dt_idx on page_details_66 pd_13 (cost=0.42..4.49 rows=1 width=8277)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_67_session_dt_idx on page_details_67 pd_14 (cost=0.42..58.62 rows=325 width=8227)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_68_session_dt_idx on page_details_68 pd_15 (cost=0.42..35.20 rows=111 width=8259)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_78_session_dt_idx on page_details_78 pd_16 (cost=0.44..1738.10 rows=4608 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_98_session_dt_idx on page_details_98 pd_17 (cost=0.44..2157.31 rows=7136 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_101_session_dt_idx on page_details_101 pd_18 (cost=0.44..2956.03 rows=9241 width=8205)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_130_session_dt_idx on page_details_130 pd_19 (cost=0.44..1683.53 rows=19656 width=8199)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m100_session_dt_idx on page_details_m100 pd_20 (cost=0.43..4.96 rows=1 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m4_session_dt_idx on page_details_m4 pd_21 (cost=0.43..659.89 rows=6097 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_134_session_dt_idx on page_details_134 pd_22 (cost=0.45..4666.25 rows=50409 width=8176)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_58_session_dt_idx on page_details_58 pd_23 (cost=0.43..7.05 rows=1 width=8362)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_69_session_dt_idx on page_details_69 pd_24 (cost=0.43..125.03 rows=348 width=8268)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_100_session_dt_idx on page_details_100 pd_25 (cost=0.43..381.13 rows=466 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_114_session_dt_idx on page_details_114 pd_26 (cost=0.43..7.80 rows=1 width=8183)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m5_session_dt_idx on page_details_m5 pd_27 (cost=0.57..4505.18 rows=50872 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_32_session_dt_idx on page_details_32 pd_28 (cost=0.43..8.44 rows=1 width=8807)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_23_session_dt_idx on page_details_23 pd_29 (cost=0.29..7.47 rows=1 width=9327)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m6_session_dt_idx on page_details_m6 pd_30 (cost=0.44..769.32 rows=7135 width=7814)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m7_session_dt_idx on page_details_m7 pd_31 (cost=0.44..11400.50 rows=14694 width=8203)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m8_session_dt_idx on page_details_m8 pd_32 (cost=0.44..6568.86 rows=8045 width=8200)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_144_session_dt_idx on page_details_144 pd_33 (cost=0.29..21.16 rows=162 width=8189)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_143_session_dt_idx on page_details_143 pd_34 (cost=0.43..1477.00 rows=16135 width=8197)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_145_session_dt_idx on page_details_145 pd_35 (cost=0.29..87.17 rows=844 width=8226)

Index Cond: (session_dt >= ((now())::date - 2))

-> Hash (cost=16117516.77..16117516.77 rows=449927377 width=226)

-> Append (cost=0.00..16117516.77 rows=449927377 width=226)

-> Seq Scan on page_details_ext_null pde (cost=0.00..1467668.52 rows=40845752 width=226)

-> Seq Scan on page_details_ext_m3 pde_1 (cost=0.00..347732.32 rows=9980132 width=226)

-> Seq Scan on page_details_ext_m2 pde_2 (cost=0.00..26146.27 rows=715527 width=226)

-> Seq Scan on page_details_ext_m1 pde_3 (cost=0.00..180093.08 rows=4793908 width=226)

-> Seq Scan on page_details_ext_5 pde_4 (cost=0.00..3056150.08 rows=82652608 width=226)

-> Seq Scan on page_details_ext_31 pde_5 (cost=0.00..4177416.08 rows=124953208 width=226)

-> Seq Scan on page_details_ext_49 pde_6 (cost=0.00..1034364.84 rows=28538484 width=226)

-> Seq Scan on page_details_ext_52 pde_7 (cost=0.00..575529.72 rows=16018272 width=226)

-> Seq Scan on page_details_ext_59 pde_8 (cost=0.00..1226617.78 rows=33054378 width=226)

-> Seq Scan on page_details_ext_60 pde_9 (cost=0.00..206925.60 rows=5920260 width=226)

-> Seq Scan on page_details_ext_61 pde_10 (cost=0.00..10599.63 rows=296463 width=226)

-> Seq Scan on page_details_ext_63 pde_11 (cost=0.00..32993.45 rows=898145 width=226)

-> Seq Scan on page_details_ext_64 pde_12 (cost=0.00..211220.00 rows=6212500 width=226)

-> Seq Scan on page_details_ext_66 pde_13 (cost=0.00..4888.44 rows=127544 width=226)

-> Seq Scan on page_details_ext_67 pde_14 (cost=0.00..5121.02 rows=135402 width=226)

-> Seq Scan on page_details_ext_68 pde_15 (cost=0.00..4284.18 rows=116218 width=226)

-> Seq Scan on page_details_ext_78 pde_16 (cost=0.00..135663.64 rows=3705564 width=226)

-> Seq Scan on page_details_ext_98 pde_17 (cost=0.00..232421.44 rows=6556944 width=226)

-> Seq Scan on page_details_ext_101 pde_18 (cost=0.00..189844.81 rows=5231481 width=226)

-> Seq Scan on page_details_ext_130 pde_19 (cost=0.00..318011.40 rows=8558640 width=226)

-> Seq Scan on page_details_ext_m100 pde_20 (cost=0.00..4914.04 rows=143504 width=226)

-> Seq Scan on page_details_ext_m4 pde_21 (cost=0.00..75878.68 rows=1994468 width=226)

-> Seq Scan on page_details_ext_134 pde_22 (cost=0.00..724264.36 rows=19192136 width=226)

-> Seq Scan on page_details_ext_58 pde_23 (cost=0.00..12171.94 rows=361394 width=331)

-> Seq Scan on page_details_ext_69 pde_24 (cost=0.00..6464.95 rows=173295 width=226)

-> Seq Scan on page_details_ext_100 pde_25 (cost=0.00..9217.39 rows=255239 width=226)

-> Seq Scan on page_details_ext_114 pde_26 (cost=0.00..11702.69 rows=358469 width=226)

-> Seq Scan on page_details_ext_m5 pde_27 (cost=0.00..1274434.84 rows=33330284 width=226)

-> Seq Scan on page_details_ext_23 pde_28 (cost=0.00..822.03 rows=25503 width=378)

-> Seq Scan on page_details_ext_32 pde_29 (cost=0.00..7011.56 rows=217756 width=378)

-> Seq Scan on page_details_ext_m6 pde_30 (cost=0.00..177039.58 rows=4616658 width=226)

-> Seq Scan on page_details_ext_m7 pde_31 (cost=0.00..188264.43 rows=5143643 width=226)

-> Seq Scan on page_details_ext_m8 pde_32 (cost=0.00..139185.56 rows=3799056 width=226)

-> Seq Scan on page_details_ext_144 pde_33 (cost=0.00..687.46 rows=16246 width=226)

-> Seq Scan on page_details_ext_143 pde_34 (cost=0.00..41053.82 rows=971482 width=226)

-> Seq Scan on page_details_ext_145 pde_35 (cost=0.00..711.14 rows=16814 width=226)

The only place an index scan is used is to filter down page_details. In my second query,
when explicitly joining single partitions an index scan is used to perform filtering, and the join as well:

--query

explain

select * from dm_ci360.page_details_5 pd
inner join dm_ci360.page_details_ext_5 pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)
where pd.session_dt >= now()::date-2;

--plan

Nested Loop (cost=1.27..1685980.38 rows=1 width=8428)

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd (cost=0.57..51267.67 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_ext_5_session_id_detail_id_idx on page_details_ext_5 pde (cost=0.69..8.31 rows=1 width=226)

Index Cond: (((session_id)::text = (pd.session_id)::text) AND ((detail_id)::text = (pd.detail_id)::text))

I just cannot figure out why the join for the parent table will not leverage the index,
but the join for a single partition will. We are running on Postgres 10, and the row counts for the tables can be found below:

Row Count
page_details -> ~413M
page_details_ext -> ~450M

Table DDL
-- page_details

CREATE TABLE dm_ci360.page_details (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    visit_id varchar(32) NULL,
    window_size_txt varchar(20) NULL,
    session_dt date NULL,
    page_url_txt varchar(1332) NULL,
    domain_nm varchar(165) NULL,
    bytes_sent_cnt int4 NULL,
    page_load_sec_cnt int8 NULL,
    page_complete_sec_cnt int8 NULL,
    protocol_nm varchar(8) NULL,
    page_desc varchar(1332) NULL,
    class1_id varchar(650) NULL,
    class2_id varchar(650) NULL,
    class3_id varchar(650) NULL,
    class4_id varchar(650) NULL,
    class5_id varchar(650) NULL,
    class6_id varchar(650) NULL,
    class7_id varchar(650) NULL,
    class8_id varchar(650) NULL,
    class9_id varchar(650) NULL,
    class10_id varchar(650) NULL,
    class11_id varchar(650) NULL,
    class12_id varchar(650) NULL,
    class13_id varchar(650) NULL,
    class14_id varchar(650) NULL,
    class15_id varchar(650) NULL,
    url_domain varchar(215) NULL,
    identity_id varchar(36) NULL,
    detail_dttm timestamp NULL,
    detail_dttm_tz timestamp NULL,
    load_dttm timestamp NULL,
    session_dt_tz date NULL,
    detail_id_hex varchar(32) NULL,
    visit_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_100 PARTITION OF dm_ci360.page_details FOR VALUES IN (100);

CREATE INDEX page_details_100_detail_dttm_idx ON dm_ci360.page_details_100 USING btree (detail_dttm)
CREATE INDEX page_details_100_identity_id_idx ON dm_ci360.page_details_100 USING btree (identity_id)
CREATE INDEX page_details_100_session_dt_idx ON dm_ci360.page_details_100 USING btree (session_dt)
CREATE INDEX page_details_100_session_id_detail_id_idx ON dm_ci360.page_details_100 USING btree (session_id, detail_id)

-- page_details_ext

CREATE TABLE dm_ci360.page_details_ext (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    active_sec_spent_on_page_cnt int4 NULL,
    seconds_spent_on_page_cnt int4 NULL,
    load_dttm timestamp NULL,
    detail_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_ext_100 PARTITION OF dm_ci360.page_details_ext FOR VALUES IN (100);

CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)
CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)
Thanks
--
Angular momentum makes the world go 'round.

Re: Join for the parent table will not leverage the index scan

From

Ron

Date:

17 August 2021, 20:15:02

I've seen a similar problem in v12, but this is different since it's a LIST partition, and I use RANGE partitions.

The bottom line is that the query optimizer thinks it cheaper to sequentially scan. Is there an index on client_id which I missed?

On 8/16/21 10:25 PM, Shrikant Bhende wrote:

Hi Ron,

Thanks for the reply and clarification.
Tables are getting analyzed regularly also did analze today as well,
Below is the test case where I tried to use the partition key in join,
but still getting the same result.
explain
select *
from dm_ci360.page_details pd
left join dm_ci360.page_details_ext pde
    on (pd.detail_id = pde.detail_id
        and pd.client_id = pde.client_id);
    
    --
    
    "QUERY PLAN"
Gather  (cost=1328436468.62..1375694672.28 rows=421291719 width=8287)
  Workers Planned: 8
  ->  Merge Left Join  (cost=1328435468.62..1333564500.38 rows=52661465 width=8287)
        Merge Cond: (((pd.detail_id)::text = (pde.detail_id)::text) AND (pd.client_id = pde.client_id))
        ->  Sort  (cost=1045342980.27..1045489637.23 rows=58662783 width=8061)
"              Sort Key: pd.detail_id, pd.client_id"
              ->  Append  (cost=0.00..24208020.84 rows=58662783 width=8061)
                    ->  Parallel Seq Scan on page_details_null pd  (cost=0.00..2425406.85 rows=5120384 width=8220)
                    ->  Parallel Seq Scan on page_details_m3 pd_1  (cost=0.00..503325.67 rows=1484767 width=8216)
                    ->  Parallel Seq Scan on page_details_m2 pd_2  (cost=0.00..41493.07 rows=158208 width=8253)
                    ->  Parallel Seq Scan on page_details_m1 pd_3  (cost=0.00..298542.32 rows=718532 width=8281)
                    ->  Parallel Seq Scan on page_details_5 pd_4  (cost=0.00..4546231.40 rows=9936540 width=8202)
                    ->  Parallel Seq Scan on page_details_31 pd_5  (cost=0.00..5351785.68 rows=13473668 width=7721)
                    ->  Parallel Seq Scan on page_details_49 pd_6  (cost=0.00..1528222.35 rows=3763935 width=7721)
                    ->  Parallel Seq Scan on page_details_52 pd_7  (cost=0.00..1005739.96 rows=2113496 width=8297)
                    ->  Parallel Seq Scan on page_details_59 pd_8  (cost=0.00..2139754.44 rows=4577244 width=8276)
                    ->  Parallel Seq Scan on page_details_60 pd_9  (cost=0.00..316209.20 rows=846820 width=8263)
                    ->  Parallel Seq Scan on page_details_61 pd_10  (cost=0.00..14790.59 rows=85759 width=8182)
                    ->  Parallel Seq Scan on page_details_63 pd_11  (cost=0.00..52206.08 rows=204008 width=8250)
                    ->  Parallel Seq Scan on page_details_64 pd_12  (cost=0.00..358858.43 rows=904143 width=8314)
                    ->  Parallel Seq Scan on page_details_66 pd_13  (cost=0.00..8647.65 rows=50365 width=8277)
                    ->  Parallel Seq Scan on page_details_67 pd_14  (cost=0.00..8507.65 rows=54465 width=8227)
                    ->  Parallel Seq Scan on page_details_68 pd_15  (cost=0.00..7667.92 rows=47192 width=8259)
                    ->  Parallel Seq Scan on page_details_78 pd_16  (cost=0.00..227673.87 rows=698287 width=8263)
                    ->  Parallel Seq Scan on page_details_98 pd_17  (cost=0.00..342905.89 rows=975589 width=8225)
                    ->  Parallel Seq Scan on page_details_101 pd_18  (cost=0.00..277631.48 rows=815948 width=8205)
                    ->  Parallel Seq Scan on page_details_130 pd_19  (cost=0.00..489453.45 rows=1409344 width=8199)
                    ->  Parallel Seq Scan on page_details_m100 pd_20  (cost=0.00..8943.50 rows=62750 width=8225)
                    ->  Parallel Seq Scan on page_details_m4 pd_21  (cost=0.00..119599.55 rows=409355 width=8195)
                    ->  Parallel Seq Scan on page_details_134 pd_22  (cost=0.00..1078678.24 rows=2791724 width=8176)
                    ->  Parallel Seq Scan on page_details_58 pd_23  (cost=0.00..19107.17 rows=114617 width=8362)
                    ->  Parallel Seq Scan on page_details_69 pd_24  (cost=0.00..11774.27 rows=56027 width=8268)
                    ->  Parallel Seq Scan on page_details_100 pd_25  (cost=0.00..14765.61 rows=83161 width=8195)
                    ->  Parallel Seq Scan on page_details_114 pd_26  (cost=0.00..17953.55 rows=112155 width=8183)
                    ->  Parallel Seq Scan on page_details_m5 pd_27  (cost=0.00..2069930.14 rows=4803014 width=8225)
                    ->  Parallel Seq Scan on page_details_32 pd_28  (cost=0.00..9655.67 rows=90767 width=8807)
                    ->  Parallel Seq Scan on page_details_23 pd_29  (cost=0.00..1183.66 rows=14966 width=9327)
                    ->  Parallel Seq Scan on page_details_m6 pd_30  (cost=0.00..331066.68 rows=766068 width=7814)
                    ->  Parallel Seq Scan on page_details_m7 pd_31  (cost=0.00..276835.86 rows=820386 width=8203)
                    ->  Parallel Seq Scan on page_details_m8 pd_32  (cost=0.00..219677.99 rows=764299 width=8200)
                    ->  Parallel Seq Scan on page_details_144 pd_33  (cost=0.00..1243.71 rows=10671 width=8189)
                    ->  Parallel Seq Scan on page_details_143 pd_34  (cost=0.00..79279.91 rows=304892 width=8196)
                    ->  Parallel Seq Scan on page_details_145 pd_35  (cost=0.00..3271.37 rows=19237 width=8226)
        ->  Materialize  (cost=283092488.35..285385333.09 rows=458568949 width=226)
              ->  Sort  (cost=283092488.35..284238910.72 rows=458568949 width=226)
"                    Sort Key: pde.detail_id, pde.client_id"
                    ->  Append  (cost=0.00..16497547.49 rows=458568949 width=226)
                          ->  Seq Scan on page_details_ext_null pde  (cost=0.00..1524481.42 rows=42223842 width=226)
                          ->  Seq Scan on page_details_ext_m3 pde_1  (cost=0.00..347731.78 rows=9980078 width=226)
                          ->  Seq Scan on page_details_ext_m2 pde_2  (cost=0.00..26437.83 rows=721783 width=226)
                          ->  Seq Scan on page_details_ext_m1 pde_3  (cost=0.00..180092.12 rows=4793812 width=226)
                          ->  Seq Scan on page_details_ext_5 pde_4  (cost=0.00..3157905.57 rows=84945757 width=226)
                          ->  Seq Scan on page_details_ext_31 pde_5  (cost=0.00..4198600.83 rows=125384283 width=226)
                          ->  Seq Scan on page_details_ext_49 pde_6  (cost=0.00..1058695.45 rows=29083145 width=226)
                          ->  Seq Scan on page_details_ext_52 pde_7  (cost=0.00..582580.50 rows=16175450 width=226)
                          ->  Seq Scan on page_details_ext_59 pde_8  (cost=0.00..1276447.65 rows=34184965 width=226)
                          ->  Seq Scan on page_details_ext_60 pde_9  (cost=0.00..209865.67 rows=5987267 width=226)
                          ->  Seq Scan on page_details_ext_61 pde_10  (cost=0.00..10846.58 rows=301558 width=226)
                          ->  Seq Scan on page_details_ext_63 pde_11  (cost=0.00..32991.51 rows=897951 width=226)
                          ->  Seq Scan on page_details_ext_64 pde_12  (cost=0.00..211218.56 rows=6212356 width=226)
                          ->  Seq Scan on page_details_ext_66 pde_13  (cost=0.00..4888.06 rows=127506 width=226)
                          ->  Seq Scan on page_details_ext_67 pde_14  (cost=0.00..5320.29 rows=139829 width=226)
                          ->  Seq Scan on page_details_ext_68 pde_15  (cost=0.00..4519.19 rows=121219 width=226)
                          ->  Seq Scan on page_details_ext_78 pde_16  (cost=0.00..138728.11 rows=3774711 width=226)
                          ->  Seq Scan on page_details_ext_98 pde_17  (cost=0.00..235653.77 rows=6628477 width=226)
                          ->  Seq Scan on page_details_ext_101 pde_18  (cost=0.00..195898.44 rows=5365744 width=226)
                          ->  Seq Scan on page_details_ext_130 pde_19  (cost=0.00..327932.65 rows=8781965 width=226)
                          ->  Seq Scan on page_details_ext_m100 pde_20  (cost=0.00..4913.38 rows=143438 width=226)
                          ->  Seq Scan on page_details_ext_m4 pde_21  (cost=0.00..79001.77 rows=2065777 width=226)
                          ->  Seq Scan on page_details_ext_134 pde_22  (cost=0.00..757767.21 rows=19952321 width=226)
                          ->  Seq Scan on page_details_ext_58 pde_23  (cost=0.00..12171.64 rows=361364 width=331)
                          ->  Seq Scan on page_details_ext_69 pde_24  (cost=0.00..6617.58 rows=176558 width=226)
                          ->  Seq Scan on page_details_ext_100 pde_25  (cost=0.00..9531.93 rows=261993 width=226)
                          ->  Seq Scan on page_details_ext_114 pde_26  (cost=0.00..11702.72 rows=358372 width=226)
                          ->  Seq Scan on page_details_ext_m5 pde_27  (cost=0.00..1300373.49 rows=33923749 width=226)
                          ->  Seq Scan on page_details_ext_23 pde_28  (cost=0.00..819.39 rows=25239 width=378)
                          ->  Seq Scan on page_details_ext_32 pde_29  (cost=0.00..7009.04 rows=217504 width=378)
                          ->  Seq Scan on page_details_ext_m6 pde_30  (cost=0.00..181575.92 rows=4720692 width=226)
                          ->  Seq Scan on page_details_ext_m7 pde_31  (cost=0.00..196632.54 rows=5332554 width=226)
                          ->  Seq Scan on page_details_ext_m8 pde_32  (cost=0.00..142816.57 rows=3877857 width=226)
                          ->  Seq Scan on page_details_ext_144 pde_33  (cost=0.00..780.22 rows=18422 width=226)
                          ->  Seq Scan on page_details_ext_143 pde_34  (cost=0.00..53050.54 rows=1255354 width=226)
                          ->  Seq Scan on page_details_ext_145 pde_35  (cost=0.00..1947.57 rows=46057 width=226)
Thanks
On Mon, Aug 16, 2021 at 9:47 AM Ron <ronljohnsonjr@gmail.com> wrote:
When were the tables last analyzed?

Also, the whole set of partitions must be scanned, since the tables are partitioned by a field other than what's in the JOIN and WHERE clauses.

On 8/13/21 7:23 AM, Shrikant Bhende wrote:
We have two tables, both have ~36 partitions.
This is my first query, which attempts to join the parent tables on the columns that have been used to create multi-column indexes for all partitions (multi-column indexes defined on session_id, detail_id in that order):

PostgreSQL version : 10
-- query

explain

select * from dm_ci360.page_details pd
inner join dm_ci360.page_details_ext pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)
where pd.session_dt >= now()::date-2;

-- plan

Hash Join (cost=36927955.75..100106605.07 rows=11 width=8355)

Hash Cond: (((pd.session_id)::text = (pde.session_id)::text) AND ((pd.detail_id)::text = (pde.detail_id)::text))

-> Append (cost=1297.33..571870.20 rows=630535 width=8130)

-> Bitmap Heap Scan on page_details_null pd (cost=1297.33..240207.85 rows=69259 width=8220)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_null_session_dt_idx (cost=0.00..1280.02 rows=69259 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m3_session_dt_idx on page_details_m3 pd_1 (cost=0.44..4.71 rows=1 width=8216)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m2_session_dt_idx on page_details_m2 pd_2 (cost=0.43..102.79 rows=621 width=8253)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m1_session_dt_idx on page_details_m1 pd_3 (cost=0.44..4.55 rows=1 width=8281)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd_4 (cost=0.57..51622.53 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Heap Scan on page_details_31 pd_5 (cost=982.61..194857.98 rows=52391 width=7721)

Recheck Cond: (session_dt >= ((now())::date - 2))

-> Bitmap Index Scan on page_details_31_session_dt_idx1 (cost=0.00..969.51 rows=52391 width=0)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_49_session_dt_idx on page_details_49 pd_6 (cost=0.45..10991.08 rows=50039 width=7721)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_52_session_dt_idx on page_details_52 pd_7 (cost=0.44..2337.94 rows=10222 width=8297)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_59_session_dt_idx on page_details_59 pd_8 (cost=0.57..24790.17 rows=50148 width=8276)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_60_session_dt_idx on page_details_60 pd_9 (cost=0.44..7292.41 rows=4259 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_61_session_dt_idx on page_details_61 pd_10 (cost=0.43..309.10 rows=704 width=8182)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_63_session_dt_idx on page_details_63 pd_11 (cost=0.43..13.20 rows=25 width=8250)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_64_session_dt_idx on page_details_64 pd_12 (cost=0.44..5.41 rows=1 width=8314)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_66_session_dt_idx on page_details_66 pd_13 (cost=0.42..4.49 rows=1 width=8277)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_67_session_dt_idx on page_details_67 pd_14 (cost=0.42..58.62 rows=325 width=8227)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_68_session_dt_idx on page_details_68 pd_15 (cost=0.42..35.20 rows=111 width=8259)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_78_session_dt_idx on page_details_78 pd_16 (cost=0.44..1738.10 rows=4608 width=8263)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_98_session_dt_idx on page_details_98 pd_17 (cost=0.44..2157.31 rows=7136 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_101_session_dt_idx on page_details_101 pd_18 (cost=0.44..2956.03 rows=9241 width=8205)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_130_session_dt_idx on page_details_130 pd_19 (cost=0.44..1683.53 rows=19656 width=8199)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m100_session_dt_idx on page_details_m100 pd_20 (cost=0.43..4.96 rows=1 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m4_session_dt_idx on page_details_m4 pd_21 (cost=0.43..659.89 rows=6097 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_134_session_dt_idx on page_details_134 pd_22 (cost=0.45..4666.25 rows=50409 width=8176)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_58_session_dt_idx on page_details_58 pd_23 (cost=0.43..7.05 rows=1 width=8362)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_69_session_dt_idx on page_details_69 pd_24 (cost=0.43..125.03 rows=348 width=8268)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_100_session_dt_idx on page_details_100 pd_25 (cost=0.43..381.13 rows=466 width=8195)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_114_session_dt_idx on page_details_114 pd_26 (cost=0.43..7.80 rows=1 width=8183)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m5_session_dt_idx on page_details_m5 pd_27 (cost=0.57..4505.18 rows=50872 width=8225)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_32_session_dt_idx on page_details_32 pd_28 (cost=0.43..8.44 rows=1 width=8807)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_23_session_dt_idx on page_details_23 pd_29 (cost=0.29..7.47 rows=1 width=9327)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m6_session_dt_idx on page_details_m6 pd_30 (cost=0.44..769.32 rows=7135 width=7814)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m7_session_dt_idx on page_details_m7 pd_31 (cost=0.44..11400.50 rows=14694 width=8203)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_m8_session_dt_idx on page_details_m8 pd_32 (cost=0.44..6568.86 rows=8045 width=8200)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_144_session_dt_idx on page_details_144 pd_33 (cost=0.29..21.16 rows=162 width=8189)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_143_session_dt_idx on page_details_143 pd_34 (cost=0.43..1477.00 rows=16135 width=8197)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_145_session_dt_idx on page_details_145 pd_35 (cost=0.29..87.17 rows=844 width=8226)

Index Cond: (session_dt >= ((now())::date - 2))

-> Hash (cost=16117516.77..16117516.77 rows=449927377 width=226)

-> Append (cost=0.00..16117516.77 rows=449927377 width=226)

-> Seq Scan on page_details_ext_null pde (cost=0.00..1467668.52 rows=40845752 width=226)

-> Seq Scan on page_details_ext_m3 pde_1 (cost=0.00..347732.32 rows=9980132 width=226)

-> Seq Scan on page_details_ext_m2 pde_2 (cost=0.00..26146.27 rows=715527 width=226)

-> Seq Scan on page_details_ext_m1 pde_3 (cost=0.00..180093.08 rows=4793908 width=226)

-> Seq Scan on page_details_ext_5 pde_4 (cost=0.00..3056150.08 rows=82652608 width=226)

-> Seq Scan on page_details_ext_31 pde_5 (cost=0.00..4177416.08 rows=124953208 width=226)

-> Seq Scan on page_details_ext_49 pde_6 (cost=0.00..1034364.84 rows=28538484 width=226)

-> Seq Scan on page_details_ext_52 pde_7 (cost=0.00..575529.72 rows=16018272 width=226)

-> Seq Scan on page_details_ext_59 pde_8 (cost=0.00..1226617.78 rows=33054378 width=226)

-> Seq Scan on page_details_ext_60 pde_9 (cost=0.00..206925.60 rows=5920260 width=226)

-> Seq Scan on page_details_ext_61 pde_10 (cost=0.00..10599.63 rows=296463 width=226)

-> Seq Scan on page_details_ext_63 pde_11 (cost=0.00..32993.45 rows=898145 width=226)

-> Seq Scan on page_details_ext_64 pde_12 (cost=0.00..211220.00 rows=6212500 width=226)

-> Seq Scan on page_details_ext_66 pde_13 (cost=0.00..4888.44 rows=127544 width=226)

-> Seq Scan on page_details_ext_67 pde_14 (cost=0.00..5121.02 rows=135402 width=226)

-> Seq Scan on page_details_ext_68 pde_15 (cost=0.00..4284.18 rows=116218 width=226)

-> Seq Scan on page_details_ext_78 pde_16 (cost=0.00..135663.64 rows=3705564 width=226)

-> Seq Scan on page_details_ext_98 pde_17 (cost=0.00..232421.44 rows=6556944 width=226)

-> Seq Scan on page_details_ext_101 pde_18 (cost=0.00..189844.81 rows=5231481 width=226)

-> Seq Scan on page_details_ext_130 pde_19 (cost=0.00..318011.40 rows=8558640 width=226)

-> Seq Scan on page_details_ext_m100 pde_20 (cost=0.00..4914.04 rows=143504 width=226)

-> Seq Scan on page_details_ext_m4 pde_21 (cost=0.00..75878.68 rows=1994468 width=226)

-> Seq Scan on page_details_ext_134 pde_22 (cost=0.00..724264.36 rows=19192136 width=226)

-> Seq Scan on page_details_ext_58 pde_23 (cost=0.00..12171.94 rows=361394 width=331)

-> Seq Scan on page_details_ext_69 pde_24 (cost=0.00..6464.95 rows=173295 width=226)

-> Seq Scan on page_details_ext_100 pde_25 (cost=0.00..9217.39 rows=255239 width=226)

-> Seq Scan on page_details_ext_114 pde_26 (cost=0.00..11702.69 rows=358469 width=226)

-> Seq Scan on page_details_ext_m5 pde_27 (cost=0.00..1274434.84 rows=33330284 width=226)

-> Seq Scan on page_details_ext_23 pde_28 (cost=0.00..822.03 rows=25503 width=378)

-> Seq Scan on page_details_ext_32 pde_29 (cost=0.00..7011.56 rows=217756 width=378)

-> Seq Scan on page_details_ext_m6 pde_30 (cost=0.00..177039.58 rows=4616658 width=226)

-> Seq Scan on page_details_ext_m7 pde_31 (cost=0.00..188264.43 rows=5143643 width=226)

-> Seq Scan on page_details_ext_m8 pde_32 (cost=0.00..139185.56 rows=3799056 width=226)

-> Seq Scan on page_details_ext_144 pde_33 (cost=0.00..687.46 rows=16246 width=226)

-> Seq Scan on page_details_ext_143 pde_34 (cost=0.00..41053.82 rows=971482 width=226)

-> Seq Scan on page_details_ext_145 pde_35 (cost=0.00..711.14 rows=16814 width=226)

The only place an index scan is used is to filter down page_details. In my second query,
when explicitly joining single partitions an index scan is used to perform filtering, and the join as well:

--query

explain

select * from dm_ci360.page_details_5 pd
inner join dm_ci360.page_details_ext_5 pde
on (pd.session_id = pde.session_id
and pd.detail_id = pde.detail_id)
where pd.session_dt >= now()::date-2;

--plan

Nested Loop (cost=1.27..1685980.38 rows=1 width=8428)

-> Index Scan using page_details_5_session_dt_idx on page_details_5 pd (cost=0.57..51267.67 rows=196574 width=8202)

Index Cond: (session_dt >= ((now())::date - 2))

-> Index Scan using page_details_ext_5_session_id_detail_id_idx on page_details_ext_5 pde (cost=0.69..8.31 rows=1 width=226)

Index Cond: (((session_id)::text = (pd.session_id)::text) AND ((detail_id)::text = (pd.detail_id)::text))

I just cannot figure out why the join for the parent table will not leverage the index,
but the join for a single partition will. We are running on Postgres 10, and the row counts for the tables can be found below:

Row Count
page_details -> ~413M
page_details_ext -> ~450M

Table DDL
-- page_details

CREATE TABLE dm_ci360.page_details (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    visit_id varchar(32) NULL,
    window_size_txt varchar(20) NULL,
    session_dt date NULL,
    page_url_txt varchar(1332) NULL,
    domain_nm varchar(165) NULL,
    bytes_sent_cnt int4 NULL,
    page_load_sec_cnt int8 NULL,
    page_complete_sec_cnt int8 NULL,
    protocol_nm varchar(8) NULL,
    page_desc varchar(1332) NULL,
    class1_id varchar(650) NULL,
    class2_id varchar(650) NULL,
    class3_id varchar(650) NULL,
    class4_id varchar(650) NULL,
    class5_id varchar(650) NULL,
    class6_id varchar(650) NULL,
    class7_id varchar(650) NULL,
    class8_id varchar(650) NULL,
    class9_id varchar(650) NULL,
    class10_id varchar(650) NULL,
    class11_id varchar(650) NULL,
    class12_id varchar(650) NULL,
    class13_id varchar(650) NULL,
    class14_id varchar(650) NULL,
    class15_id varchar(650) NULL,
    url_domain varchar(215) NULL,
    identity_id varchar(36) NULL,
    detail_dttm timestamp NULL,
    detail_dttm_tz timestamp NULL,
    load_dttm timestamp NULL,
    session_dt_tz date NULL,
    detail_id_hex varchar(32) NULL,
    visit_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_100 PARTITION OF dm_ci360.page_details FOR VALUES IN (100);

CREATE INDEX page_details_100_detail_dttm_idx ON dm_ci360.page_details_100 USING btree (detail_dttm)
CREATE INDEX page_details_100_identity_id_idx ON dm_ci360.page_details_100 USING btree (identity_id)
CREATE INDEX page_details_100_session_dt_idx ON dm_ci360.page_details_100 USING btree (session_dt)
CREATE INDEX page_details_100_session_id_detail_id_idx ON dm_ci360.page_details_100 USING btree (session_id, detail_id)

-- page_details_ext

CREATE TABLE dm_ci360.page_details_ext (
    dml_id int4 NULL,
    dml_ts timestamp NULL,
    dml_ts_utc timestamp NULL,
    dml_type varchar(1) NULL,
    dwh_job_id int4 NULL,
    ins_dwh_job_id int4 NULL,
    upd_dwh_job_id int4 NULL,
    deleted_flag varchar(1) NULL,
    processed_dttm timestamp NULL,
    valid_from_dttm timestamp(0) NULL,
    valid_to_dttm timestamp(0) NULL,
    ccd varchar(2000) NULL,
    client_id int4 NULL,
    detail_id varchar(32) NULL,
    session_id varchar(29) NULL,
    active_sec_spent_on_page_cnt int4 NULL,
    seconds_spent_on_page_cnt int4 NULL,
    load_dttm timestamp NULL,
    detail_id_hex varchar(32) NULL,
    session_id_hex varchar(29) NULL
)
PARTITION BY LIST (client_id);

CREATE TABLE dm_ci360.page_details_ext_100 PARTITION OF dm_ci360.page_details_ext FOR VALUES IN (100);

CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)
CREATE INDEX page_details_ext_100_session_id_detail_id_idx ON dm_ci360.page_details_ext_100 USING btree (session_id, detail_id)
Thanks
--
Angular momentum makes the world go 'round.

--
Angular momentum makes the world go 'round.