Query plans not identical for `id in(1,2,3)` and `(id=1 or id=2 or id=3)`

On Sat, 2024-03-09 at 23:08 +0400, Ilya Basin wrote:

I have a list of bigint keys and I need to retrieve rows by these keys.
Normally, I would split this list into pages of size 900 and perform
several `SELECT ... WHERE key in($1,$2,...)`. However, the proprietary
ORM we use can only produce this SQL:
`SELECT ... WHERE (key=$1 or key=$2 or ...)`.
Surprisingly, PostgreSQL planner treats these two SQLs differently:

Is it possible to configure PostgreSQL 12.16 to treat the second query as the first?

No, that is currently not possible.

Yours,
Laurenz Albe

Ilya Basin schrieb am 09.03.2024 um 20:08:

Hi List.

I have a list of bigint keys and I need to retrieve rows by these keys. Normally, I would split this list into pages of size 900 and perform several `SELECT ... WHERE key in($1,$2,...)`. However, the proprietary ORM we use can only produce this SQL: `SELECT ... WHERE (key=$1 or key=$2 or ...)`. Surprisingly, PostgreSQL planner treats these two SQLs differently:

- ```select * FROM "audittrail$referencelogline" where id in ( 1 , 2 , 3 )```

Index Scan
https://i.stack.imgur.com/dr8oz.png

- ```select * FROM "audittrail$referencelogline" where id = 1 or id = 2 or id = 3```

A lot of "Bitmap Index Scan" for each value
https://i.stack.imgur.com/dnErs.png

Is it possible to configure PostgreSQL 12.16 to treat the second query as the first?

Can you convince your obfuscation layer to send an array value (containing all IDs) and change the query to:

select * FROM "audittrail$referencelogline" where id = any(?)

Laurenz thanks for the info.

Thomas no I can't.

-------- Original Message --------
From: Thomas Kellerer [mailto:shammat@gmx.net]
Sent: Sunday, March 10, 2024 at 11:58 UTC
To: pgsql-general@lists.postgresql.org
Subject: Query plans not identical for `id in(1,2,3)` and `(id=1 or id=2 or id=3)`

Ilya Basin schrieb am 09.03.2024 um 20:08:
Hi List.

I have a list of bigint keys and I need to retrieve rows by these keys. Normally, I would split this list into pages of size 900 and perform several `SELECT ... WHERE key in($1,$2,...)`. However, the proprietary ORM we use can only produce this SQL: `SELECT ... WHERE (key=$1 or key=$2 or ...)`. Surprisingly, PostgreSQL planner treats these two SQLs differently:

- ```select * FROM "audittrail$referencelogline" where id in ( 1 , 2 , 3 )```

Index Scan
https://i.stack.imgur.com/dr8oz.png

- ```select * FROM "audittrail$referencelogline" where id = 1 or id = 2 or id = 3```

A lot of "Bitmap Index Scan" for each value
https://i.stack.imgur.com/dnErs.png

Is it possible to configure PostgreSQL 12.16 to treat the second query as the first?

Can you convince your obfuscation layer to send an array value (containing all IDs) and change the query to:

    select * FROM "audittrail$referencelogline" where id = any(?)