Re: Index is not using - Mailing list pgsql-performance
| From | K P Manoj |
|---|---|
| Subject | Re: Index is not using |
| Date | |
| Msg-id | CAMVgnQ4ra5D6ReoJgFZ75oh_2UTpDBXLhFSng1gOKn3aCgsu_A@mail.gmail.com Whole thread Raw |
| In response to | Re: Index is not using ("Albe Laurenz" <laurenz.albe@wien.gv.at>) |
| Responses |
Re: Index is not using
("Albe Laurenz" <laurenz.albe@wien.gv.at>)
|
| List | pgsql-performance |
Hi Albe,
Thank you for your reply ,
Please find the details of table description
test=# \d xxx
Table "public.xxx"
Column | Type | Modifiers
------------------------------+-----------------------------+-----------
crawler_id | bigint |
effective_org | character varying(255) |
reverse_pd | character varying(255) |
Indexes:
"xxx_rev_pd_idx1" btree (reverse_pd)
test =#\d tmp
Table "public.tmp"
Column | Type | Modifiers
--------------------+------------------------+-----------
id | bigint |
mdc_domain_reverse | character varying(255) |
Indexes:
"tmp_idx1" btree (mdc_domain_reverse)
"tmp_txt_idx_mdc" btree (mdc_domain_reverse varchar_pattern_ops)
test=# EXPLAIN select xxx.* from xxx xxx where exists (select 1 from tmp where mdc_domain_reverse like 'ttt' || '.%');
QUERY PLAN
----------------------------------------------------------------------------------------------------------
Result (cost=0.03..2249.94 rows=13591 width=3141)
One-Time Filter: $0
InitPlan 1 (returns $0)
-> Index Only Scan using tmp_txt_idx_mdc on tmp (cost=0.00..4.27 rows=144 width=0)
Index Cond: ((mdc_domain_reverse ~>=~ 'ttt.'::text) AND (mdc_domain_reverse ~<~ 'ttt/'::text))
Filter: ((mdc_domain_reverse)::text ~~ 'ttt.%'::text)
-> Seq Scan on xxx (cost=0.00..2249.91 rows=13591 width=3141)
(7 rows)
saleshub=# EXPLAIN select xxx.* from xxx xxx where exists (select 1 from tmp where mdc_domain_reverse like xxx.reverse_pd || '.%');
QUERY PLAN
-------------------------------------------------------------------------------------------
Nested Loop Semi Join (cost=0.00..341301641.67 rows=68 width=3141)
Join Filter: ((tmp.mdc_domain_reverse)::text ~~ ((xxx.reverse_pd)::text || '.%'::text))
-> Seq Scan on xxx (cost=0.00..2249.91 rows=13591 width=3141)
-> Materialize (cost=0.00..31811.93 rows=1442062 width=18)
-> Seq Scan on tmp (cost=0.00..24601.62 rows=1442062 width=18)
(5 rows)
My question was any chance to use query planner with above index ? or i want to change the query ?
Regards
Manoj K P
On Mon, Nov 12, 2012 at 2:01 PM, Albe Laurenz <laurenz.albe@wien.gv.at> wrote:
I don't really understand what your problem is, but ifK P Manoj wrote:
> I am facing query performance in one of my testing server.
> How i can create index with table column name ?
> EXPLAIN select xxx.* from xxx xxx where exists (select 1 from tmp
where mdc_domain_reverse like
> xxx.reverse_pd || '.%');
> QUERY PLAN
>
------------------------------------------------------------------------
-------------------
> Nested Loop Semi Join (cost=0.00..315085375.74 rows=63 width=3142)
> Join Filter: ((tmp.mdc_domain_reverse)::text ~~
((xxx.reverse_pd)::text || '.%'::text))
> -> Seq Scan on xxx (cost=0.00..6276.47 rows=12547 width=3142)
> -> Materialize (cost=0.00..31811.93 rows=1442062 width=17)
> -> Seq Scan on tmp (cost=0.00..24601.62 rows=1442062
width=17)
>
> saleshub=# EXPLAIN create table tmp2 as select xxx.* from xxx xxx
where exists (select 1 from tmp
> where mdc_domain_reverse like 'moc.ytirucesspc%') ;
>
QUERY PLAN
>
------------------------------------------------------------------------
------------------------------
> ------------------------------------------
> Result (cost=0.06..6276.53 rows=12547 width=3142)
> One-Time Filter: $0
> InitPlan 1 (returns $0)
> -> Index Scan using tmp_txt_idx_mdc on tmp (cost=0.00..8.53
rows=144 width=0)
> Index Cond: (((mdc_domain_reverse)::text ~>=~
'moc.ytirucesspc'::text) AND
> ((mdc_domain_reverse)::text ~<~ 'moc.ytirucesspd'::text))
> Filter: ((mdc_domain_reverse)::text ~~
'moc.ytirucesspc%'::text)
> -> Seq Scan on xxx (cost=0.00..6276.47 rows=12547 width=3142)
you are complaining that no index is used for the LIKE
condition in the first query, you're out of luck:
The planner has no way of knowing if the contents of
xxx.reverse_pd start with "%" or not.
Yours,
Laurenz Albe
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