Re: 3000x Slower query when using Foreign Data Wrapper vs. local - Mailing list pgsql-performance

Hi Mohammad,

                                 I think it's not enable "use_remote_estimate" during the creation of the foreign table

http://www.postgresql.org/docs/9.4/static/postgres-fdw.html

use_remote_estimate

This option, which can be specified for a foreign table or a foreign server, controls whether postgres_fdw issues remote EXPLAIN commands to obtain cost estimates. A setting for a foreign table overrides any setting for its server, but only for that table. The default is false.

try it

Bye

2015-10-11 10:05 GMT+02:00 Mohammad Habbab <moh.habbab@gmail.com>:

Hi there, 

If it's possible, I would really appreciate any hints or help on an issue I've been facing lately.

I'm running two instance of Postgres locally: 9.4.4 (operational db) and 9.5beta1 (analytical db). I've already imported schema to analytical db and while doing the following query I find very different query plans being executed:

Query:

EXPLAIN ANALYZE VERBOSE SELECT

    o.id AS id,

    o.company_id AS company_id,

    o.created_at::date AS created_at,

    COALESCE(o.assignee_id, 0) AS assignee_id,

    (o.tax_treatment)::text AS tax_treatment,

    COALESCE(o.tax_override, 0) AS tax_override,

    COALESCE(o.stock_location_id, 0) AS stock_location_id,

    COALESCE(l.label, 'N/A')::text AS stock_location_name,

    COALESCE(sa.country, 'N/A')::text AS shipping_address_country,

    COALESCE(o.tags, ARRAY[]::text[]) AS tags

  FROM orders AS o

    INNER JOIN locations AS l ON l.id = o.stock_location_id

    INNER JOIN addresses AS sa ON sa.id = o.shipping_address_id

  WHERE o.account_id = <some_value> AND l.account_id = <another_value> LIMIT 10;

Plan when I run it locally on operational db:

Limit  (cost=747.62..811.46 rows=1 width=76) (actual time=28.208..28.397 rows=10 loops=1)

Output: o.id, o.company_id, ((o.created_at)::date), (COALESCE(o.assignee_id, 0)), ((o.tax_treatment)::text), (COALESCE(o.tax_override, 0::numeric)), (COALESCE(o.stock_location_id, 0)), ((COALESCE(l.label, 'N/A'::character varying))::text), ((COALESCE(sa.country, 'N/A'::character varying))::text), (COALESCE(o.tags, '{}'::character varying[]))

->  Nested Loop  (cost=747.62..811.46 rows=1 width=76) (actual time=28.208..28.395 rows=10 loops=1)

      Output: o.id, o.company_id, (o.created_at)::date, COALESCE(o.assignee_id, 0), (o.tax_treatment)::text, COALESCE(o.tax_override, 0::numeric), COALESCE(o.stock_location_id, 0), (COALESCE(l.label, 'N/A'::character varying))::text, (COALESCE(sa.country, 'N/A'::character varying))::text, COALESCE(o.tags, '{}'::character varying[])

      ->  Nested Loop  (cost=747.19..807.15 rows=1 width=73) (actual time=28.164..28.211 rows=10 loops=1)

            Output: o.id, o.company_id, o.created_at, o.assignee_id, o.tax_treatment, o.tax_override, o.stock_location_id, o.tags, o.shipping_address_id, l.label

            ->  Index Scan using index_locations_on_account_id on public.locations l  (cost=0.29..8.31 rows=1 width=20) (actual time=0.025..0.025 rows=1 loops=1)

                  Output: l.id, l.address1, l.address2, l.city, l.country, l.zip_code, l.suburb, l.state, l.label, l.status, l.latitude, l.longitude, l.created_at, l.updated_at, l.account_id, l.holds_stock

                  Index Cond: (l.account_id = 18799)

            ->  Bitmap Heap Scan on public.orders o  (cost=746.90..798.71 rows=13 width=57) (actual time=28.133..28.176 rows=10 loops=1)

                  Output: o.id, o.account_id, o.company_id, o.status, o.invoice_number, o.reference_number, o.due_at, o.issued_at, o.user_id, o.notes, o.created_at, o.updated_at, o.order_number, o.billing_address_id, o.shipping_address_id, o.payment_status, o.email, o.fulfillment_status, o.phone_number, o.assignee_id, o.tax_treatment, o.tax_override, o.tax_label_override, o.stock_location_id, o.currency_id, o.source, o.source_url, o.demo, o.invoice_status, o.ship_at, o.source_id, o.search, o.default_price_list_id, o.contact_id, o.return_status, o.tags, o.packed_status, o.returning_status, o.shippability_status, o.backordering_status

                  Recheck Cond: ((o.stock_location_id = l.id) AND (o.account_id = 18799))

                  Heap Blocks: exact=7

                  ->  BitmapAnd  (cost=746.90..746.90 rows=13 width=0) (actual time=23.134..23.134 rows=0 loops=1)

                        ->  Bitmap Index Scan on index_orders_on_stock_location_id_manual  (cost=0.00..18.02 rows=745 width=0) (actual time=9.282..9.282 rows=40317 loops=1)

                              Index Cond: (o.stock_location_id = l.id)

                        ->  Bitmap Index Scan on index_orders_on_account_id  (cost=0.00..718.94 rows=38735 width=0) (actual time=9.856..9.856 rows=40317 loops=1)

                              Index Cond: (o.account_id = 18799)

      ->  Index Scan using addresses_pkey on public.addresses sa  (cost=0.43..4.30 rows=1 width=11) (actual time=0.015..0.016 rows=1 loops=10)

            Output: sa.id, sa.company_id, sa.address1, sa.city, sa.country, sa.zip_code, sa.created_at, sa.updated_at, sa.suburb, sa.state, sa.label, sa.status, sa.address2, sa.phone_number, sa.email, sa.company_name, sa.latitude, sa.longitude, sa.first_name, sa.last_name

            Index Cond: (sa.id = o.shipping_address_id)

 Planning time: 1.136 ms

 Execution time: 28.621 ms

(23 rows)

Plan when I run it from analytical db via FDW:

Limit  (cost=300.00..339.95 rows=1 width=1620) (actual time=7630.240..82368.326 rows=10 loops=1)

   Output: o.id, o.company_id, ((o.created_at)::date), (COALESCE(o.assignee_id, 0)), ((o.tax_treatment)::text), (COALESCE(o.tax_override, '0'::numeric)), (COALESCE(o.stock_location_id, 0)), ((COALESCE(l.label, 'N/A'::character varying))::

text), ((COALESCE(sa.country, 'N/A'::character varying))::text), (COALESCE(o.tags, '{}'::character varying[]))

   ->  Nested Loop  (cost=300.00..339.95 rows=1 width=1620) (actual time=7630.238..82368.314 rows=10 loops=1)

         Output: o.id, o.company_id, (o.created_at)::date, COALESCE(o.assignee_id, 0), (o.tax_treatment)::text, COALESCE(o.tax_override, '0'::numeric), COALESCE(o.stock_location_id, 0), (COALESCE(l.label, 'N/A'::character varying))::text,

 (COALESCE(sa.country, 'N/A'::character varying))::text, COALESCE(o.tags, '{}'::character varying[])

         Join Filter: (o.shipping_address_id = sa.id)

         Rows Removed by Join Filter: 19227526

         ->  Nested Loop  (cost=200.00..223.58 rows=1 width=1108) (actual time=69.758..69.812 rows=10 loops=1)

               Output: o.id, o.company_id, o.created_at, o.assignee_id, o.tax_treatment, o.tax_override, o.stock_location_id, o.tags, o.shipping_address_id, l.label

               Join Filter: (o.stock_location_id = l.id)

               Rows Removed by Join Filter: 18

               ->  Foreign Scan on remote.orders o  (cost=100.00..111.67 rows=1 width=592) (actual time=68.009..68.014 rows=10 loops=1)

                     Output: o.id, o.account_id, o.company_id, o.status, o.invoice_number, o.reference_number, o.due_at, o.issued_at, o.user_id, o.notes, o.created_at, o.updated_at, o.order_number, o.billing_address_id, o.shipping_address

_id, o.payment_status, o.email, o.fulfillment_status, o.phone_number, o.assignee_id, o.tax_treatment, o.tax_override, o.tax_label_override, o.stock_location_id, o.currency_id, o.source, o.source_url, o.demo, o.invoice_status, o.ship_at, o

.source_id, o.search, o.default_price_list_id, o.contact_id, o.return_status, o.tags, o.packed_status, o.returning_status, o.shippability_status, o.backordering_status

                     Remote SQL: SELECT id, company_id, created_at, shipping_address_id, assignee_id, tax_treatment, tax_override, stock_location_id, tags FROM public.orders WHERE ((account_id = 18799))

               ->  Foreign Scan on remote.locations l  (cost=100.00..111.90 rows=1 width=520) (actual time=0.174..0.174 rows=3 loops=10)

                     Output: l.id, l.address1, l.address2, l.city, l.country, l.zip_code, l.suburb, l.state, l.label, l.status, l.latitude, l.longitude, l.created_at, l.updated_at, l.account_id, l.holds_stock

                     Remote SQL: SELECT id, label FROM public.locations WHERE ((account_id = 18799))

         ->  Foreign Scan on remote.addresses sa  (cost=100.00..114.50 rows=150 width=520) (actual time=0.634..8029.415 rows=1922754 loops=10)

               Output: sa.id, sa.company_id, sa.address1, sa.city, sa.country, sa.zip_code, sa.created_at, sa.updated_at, sa.suburb, sa.state, sa.label, sa.status, sa.address2, sa.phone_number, sa.email, sa.company_name, sa.latitude, sa.l

ongitude, sa.first_name, sa.last_name

               Remote SQL: SELECT id, country FROM public.addresses

 Planning time: 0.209 ms

 Execution time: 82391.610 ms

(21 rows)

Time: 82393.211 ms

What am I doing wrong ? really appreciate any guidance possible. Thank you very much for taking the time to helping me with this.

Best Regards,

Mohammad

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Matteo Durighetto

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