public inbox for [email protected]  

help / color / mirror / Atom feed

From: Jim Jones <[email protected]>
To: Daniil Davydov <[email protected]>
Cc: Soumya S Murali <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Stepan Neretin <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Fix bug with accessing to temporary tables of other sessions
Date: Fri, 10 Apr 2026 12:28:59 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAJDiXgi0JFk0f2KWWQkzLBC5P7erX9WP18qqnbi-rjZ-K-P=3w@mail.gmail.com>
References: <CAJDiXghdFcZ8=nh4G69te7iRr3Q0uFyXxb3ZdG09_GTNZXwH0g@mail.gmail.com>
	<CAJDiXgi7tWm_y0i7kD8fMxGe=86_W-hMxyQS+g7-7cdTzd-KRQ@mail.gmail.com>
	<CAMtXxw_ta_9i=uPJMvGueOBc04crmraJXcyJhN0K=Wu9aa2rog@mail.gmail.com>
	<[email protected]>
	<[email protected]>
	<CAJDiXgh9g4TEyF3kWCiBgHX6QbpATZtxTfrQuBCKxUO5=nZBOw@mail.gmail.com>
	<[email protected]>
	<CAJDiXgihovkP6DMAFyJtYF4JSAjvKmiRVbF5R5n3SA=Yag32_w@mail.gmail.com>
	<CAMtXxw8pHLH9+mG3wxsF8f=Y+pHqTNP8X1UmZQPkRL9pZ5aF2w@mail.gmail.com>
	<[email protected]>
	<[email protected]>
	<CAJDiXgiAObr4c+PTWSS19vcohrFSDLK3MC5FK3TekMB3U3DjfQ@mail.gmail.com>
	<[email protected]>
	<CAJDiXghBO_TqvHOSui8MOxiFmwLT20+SAnH5nW1rpWHk7Jwffg@mail.gmail.com>
	<[email protected]>
	<CAJDiXgi0JFk0f2KWWQkzLBC5P7erX9WP18qqnbi-rjZ-K-P=3w@mail.gmail.com>

Hi Daniil

On 10/04/2026 09:10, Daniil Davydov wrote:
> Having both checks might look a bit redundant since the read stream will
> eventually call the StartReadBuffersImpl function. On the other hand, there are
> many places which are checking this restriction even if subsequent functions
> (from bufmgr) also have this check.
> 
> So, I'll keep both checks and a bit reduce the comments in the bufmgr.c .

Putting this check a level deeper sounds good to me.

> BTW, what do you think about making this comment less "concrete"? :
> # SELECT via index scan from other session.
> # Sequential scans are blocked at read_stream_begin_relation(); index scans
> # bypass that path entirely and reach ReadBufferExtended() in bufmgr.c
> # (nbtree's _bt_getbuf calls ReadBuffer directly for individual page fetches).
> # enable_seqscan=off forces the planner to use the index.
> 
> I mean that if the described logic changes, this comment will become confusing.
> We can describe the test in general words. For example :
> # Index scans can use a different code path from the one sequential scans are
> # following. Make sure that we cannot access other sessions' temp tables during
> # index scan either.

+1

Yeah, it's indeed too verbose. I guess these comments were originally
just for me so I wouldn't get too confused along the way :)

I don't have anything else to add at this point. Unless there are any
objections, I'll mark the CF entry as 'Ready for Committer.'

Thanks!

Best, Jim

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: Re: Fix bug with accessing to temporary tables of other sessions
  In-Reply-To: <[email protected]>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox