Postgres Pro
Downloads
Home   >   mailing lists

Re: Scans are offloaded to SeqScan instead of CustomScan when there are multiple relations in the same query - Mailing list pgsql-hackers

From Amin
Subject Re: Scans are offloaded to SeqScan instead of CustomScan when there are multiple relations in the same query
Date
Msg-id CAF-KA8-rViwvUVptnmacRfh9DvuMSE_3sWA7rWQzZFMevnLxCA@mail.gmail.com
Whole thread Raw
In response to Scans are offloaded to SeqScan instead of CustomScan when there are multiple relations in the same query  (Amin <amin.fallahi@gmail.com>)
Responses Re: Scans are offloaded to SeqScan instead of CustomScan when there are multiple relations in the same query
List pgsql-hackers
Tree view
To simplify: Can CustomScan scan multiple relations in the same query or it will always be assigned to one or zero relations?

On Fri, Apr 14, 2023 at 4:33 PM Amin <amin.fallahi@gmail.com> wrote:
Hi there,

In my implementation of CustomScan, when I have a query that scans multiple tables (select c from t1,t2,t3), the planner always picks one table to be scanned by CustomScan and offloads the rest to SeqScan. I tried assigning a cost of 0 to the CustomScan path, but still not working. BeginCustomScan gets executed, ExecCustomScan is skipped, and then EndCustomScan is executed for all the tables that are offloaded to Seq Scan. EXPLAIN shows that always only one table is picked to be executed by CustomScan. Any idea what I might be doing wrong? Like a value in a struct I might be setting incorrectly?

Thanks!

pgsql-hackers by date:

Previous
From: Justin Pryzby
Date:
Subject: Re: Fix typos and inconsistencies for v16
Next
From: Peter Geoghegan
Date:
Subject: Re: check_strxfrm_bug()