Обсуждение: Possible micro-optimization in CacheInvalidateHeapTuple

CacheInvalidateHeapTuple currently does the following tests first; would there be a performance improvement to testing
thesystem relation case first? We're almost never in bootstrap mode, so that test is almost always a waste. Is there
anyreason 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
incatcaches and can't affect * the relcache either. */if (!IsSystemRelation(relation))    return;
 
-- 
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com

Jim Nasby <Jim.Nasby@BlueTreble.com> writes:
> CacheInvalidateHeapTuple currently does the following tests first; would there be a performance improvement to
testingthe system relation case first? We're almost never in bootstrap mode, so that test is almost always a waste. Is
thereany 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.
        regards, tom lane

On 10/13/14, 8:28 PM, Tom Lane wrote:
> Jim Nasby <Jim.Nasby@BlueTreble.com> writes:
>> CacheInvalidateHeapTuple currently does the following tests first; would there be a performance improvement to
testingthe system relation case first? We're almost never in bootstrap mode, so that test is almost always a waste. Is
thereany 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.
--
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com

On 2014-10-21 19:06:41 -0500, Jim Nasby wrote:
> On 10/13/14, 8:28 PM, Tom Lane wrote:
> >Jim Nasby <Jim.Nasby@BlueTreble.com> writes:
> >>CacheInvalidateHeapTuple currently does the following tests first; would there be a performance improvement to
testingthe system relation case first? We're almost never in bootstrap mode, so that test is almost always a waste. Is
thereany 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.

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services