Re: Partitioning and performance

From: Ravi Krishna <sravikrishna3(at)gmail(dot)com>
To: Jan Lentfer <Jan(dot)Lentfer(at)web(dot)de>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Partitioning and performance
Date: 2015-05-28 16:25:42
Message-ID: CACER=P1tywffzivJg=JxTpkW-6Hc593KWo6L7v7dy7FKXu2kSQ@mail.gmail.com
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> Have you set up constraints on the partitions? The planner needs to know
> what is in the child tables so it can avoid scanning them.

Yes. each child table is defined as follows

CREATE TABLE TSTESTING.ACCOUNT_PART1

( CHECK (ACCOUNT_ROW_INST BETWEEN 1001 and 271660))

INHERITS (TSTESTING.ACCOUNT);

ALTER TABLE TSTESTING.ACCOUNT_PART1 ADD CONSTRAINT ACCOUNT_PART1_PKEY
PRIMARY KEY (ACCOUNT_ROW_INST);

Perhaps I was not clear. The planner is excluding partitions which can
not contain the rows looked up in the WHERE clause. However it is
still scanning the parent table.

Aggregate (cost=8.45..8.46 rows=1 width=0)
-> Append (cost=0.00..8.44 rows=2 width=0)
-> Seq Scan on account (cost=0.00..0.00 rows=1 width=0)
Filter: (account_row_inst = 101)
-> Index Only Scan using account_part1_pkey on account_part1
(cost=0.42..8.44 rows=1 width=0)
Index Cond: (account_row_inst = 101)
(6 rows)

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