Re: issue partition scan - Mailing list pgsql-performance

From Christophe Pettus
Subject Re: issue partition scan
Date
Msg-id 366856CE-2043-4163-9753-A735B02E81EA@thebuild.com
Whole thread Raw
In response to issue partition scan  (Nagaraj Raj <nagaraj.sf@yahoo.com>)
Responses Re: issue partition scan
List pgsql-performance
> On May 25, 2021, at 15:50, Nagaraj Raj <nagaraj.sf@yahoo.com> wrote:
>
> SELECT
>         t2.cid_hash AS BILLG_ACCT_CID_HASH ,
>         t2.proxy_id AS INDVDL_ENTITY_PROXY_ID ,
>         t2.accs_mthd AS ACCS_MTHD_CID_HASH
> FROM
>         public.sub t2
> Inner join acc t3 on t3.cid_hash = t2.cid_hash
> Left join sub_soc t4 on  (t2.accs_mthd = t4.accs_mthd
>   AND t2.cid_hash = t4.cid_hash)
> WHERE
>          ( ( (t3.acct = 'I' AND t3.acct_sub IN  ( '4',
> '5' ) )  OR t2.ban IN  ( '00','01','02','03','04','05' ) )
>     OR (t4.soc = 'NFWJYW0' AND t4.curr_ind = 'Y') );

As written, with the OR, it cannot exclude any partitions from the query.  The records returned will be from two merged
sets:

1. Those that have sub_soc.soc = 'NFWJYW0' and sub_soc.curr_ind = 'Y'

It can use constraint exclusion on these to only scan applicable partitions.

2. Those that have (acc.acct = 'I' AND acc.acct_sub IN  ( '4', '5' ) )  OR sub.ban IN  ( '00','01','02','03','04','05'
)

It can't use constraint exclusion on these, since results can come from any partition.


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