Re: issue partition scan

> On May 25, 2021, at 15:50, Nagaraj Raj <nagaraj(dot)sf(at)yahoo(dot)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.