Re: Possible micro-optimization in CacheInvalidateHeapTuple

From: Andres Freund <andres(at)2ndquadrant(dot)com>
To: Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Possible micro-optimization in CacheInvalidateHeapTuple
Date: 2015-01-04 00:39:02
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On 2014-10-21 19:06:41 -0500, Jim Nasby wrote:
> On 10/13/14, 8:28 PM, Tom Lane wrote:
> >Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> writes:
> >>CacheInvalidateHeapTuple currently does the following tests first; would there be a performance improvement to testing the system relation case first? We're almost never in bootstrap mode, so that test is almost always a waste. Is there any reason not to switch the two?
> >> /* Do nothing during bootstrap */
> >> if (IsBootstrapProcessingMode())
> >> return;
> >
> >> /*
> >> * We only need to worry about invalidation for tuples that are in system
> >> * relations; user-relation tuples are never in catcaches and can't affect
> >> * the relcache either.
> >> */
> >> if (!IsSystemRelation(relation))
> >> return;
> >
> >You're assuming that IsSystemRelation() is safe to apply during bootstrap
> >mode. Even if it is, I don't see the point of messing with this.
> >IsBootstrapProcessingMode() is a macro expanding to one comparison
> >instruction.
> Comment patch to that effect attached.

That doesn't seem worth the effort of apply a patch and tracking in the
CF. Marked as returned with feedback.


Andres Freund

Andres Freund
PostgreSQL Development, 24x7 Support, Training & Services

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