Horton

Re: using index or check in ALTER TABLE SET NOT NULL

Ildar Musin <i.musin@postgrespro.ru>

View thread View on postgr.es
From: Ildar Musin <i.musin@postgrespro.ru>
To: Sergei Kornilov <sk@zsrv.org>, Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, Stephen Frost <sfrost@snowman.net>, Robert Haas <robertmhaas@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2018-03-15T14:31:50Z
Lists: pgsql-hackers 
Hello Sergei,

On 10.03.2018 12:35, Sergei Kornilov wrote:
> Hello My patch does not apply after commit
> 5748f3a0aa7cf78ac6979010273bd9d50869bb8e. Here is update to current
> master. Not null constraint is immutable too, so here is no changes
> in PartConstraintImpliedByRelConstraint excepts rename and comments
> fix.
>
> In this patch version i also revert tests to v4 state: i use DEBUG
> ereport instead INFO and code path not tested. Please tell me if i
> must change tests some way.
>
> regards, Sergei
>

Ok, I can't think of any other ways to test it so I have to agree with
Tom Lane i.e. rely only on coverage. (There also were another suggestion
to use statistics [select seq_scan from pg_stat_user_tables where
relid='test'::regclass] which show number of table scans. But statistics
is collected by stat collector process with some latency and hence
cannot be reliable for tests).

Patch seems correct to me, it applies and compiles cleanly, docs
compiles as well, tests pass. Changed status to Ready for Committer.

-- 
Ildar Musin
i.musin@postgrespro.ru

Commits

  1. Avoid using INFO elevel for what are fundamentally debug messages.

  2. Revert setting client_min_messages to 'debug1' in new tests.

  3. Allow ALTER TABLE .. SET NOT NULL to skip provably unnecessary scans.

  4. Improve predtest.c's internal docs, and enhance its functionality a bit.