Re: Avoid double lookup in pgstat_fetch_stat_tabentry()

Hi,

On 11/18/22 6:32 PM, Andres Freund wrote:
> Hi,
>
> On 2022-11-18 11:09:43 +0100, Drouvot, Bertrand wrote:
>>> Furthermore, the pgstat_fetch_stat_tabentry() can just be a
>>> static inline function.
>
> I think that's just premature optimization for something like this. The
> function call overhead on accessing stats can't be a relevant factor - the
> increase in code size is more likely to matter (but still unlikely).
>
>
>> Good point. While at it, why not completely get rid of
>> pgstat_fetch_stat_tabentry_ext(), like in v2 the attached?
>
> -1, I don't think spreading the IsSharedRelation() is a good idea. It costs
> more code than it saves.
>

Got it, please find attached V3: switching back to the initial proposal and implementing Bharath's comment (getting rid of the local variable tabentry).

Out of curiosity, here are the sizes (no debug):

- Current code (no patch)

$ size ./src/backend/utils/adt/pgstatfuncs.o ./src/backend/utils/activity/pgstat_relation.o
text data bss dec hex filename
24974 0 0 24974 618e ./src/backend/utils/adt/pgstatfuncs.o
7353 64 0 7417 1cf9 ./src/backend/utils/activity/pgstat_relation.o

- IsSharedRelation() spreading

$ size ./src/backend/utils/adt/pgstatfuncs.o ./src/backend/utils/activity/pgstat_relation.o
text data bss dec hex filename
25304 0 0 25304 62d8 ./src/backend/utils/adt/pgstatfuncs.o
7249 64 0 7313 1c91 ./src/backend/utils/activity/pgstat_relation.o

- inline function

$ size ./src/backend/utils/adt/pgstatfuncs.o ./src/backend/utils/activity/pgstat_relation.o
text data bss dec hex filename
25044 0 0 25044 61d4 ./src/backend/utils/adt/pgstatfuncs.o
7249 64 0 7313 1c91 ./src/backend/utils/activity/pgstat_relation.o

- V3 attached

$ size ./src/backend/utils/adt/pgstatfuncs.o ./src/backend/utils/activity/pgstat_relation.o
text data bss dec hex filename
24974 0 0 24974 618e ./src/backend/utils/adt/pgstatfuncs.o
7323 64 0 7387 1cdb ./src/backend/utils/activity/pgstat_relation.o

I'd vote for V3 for readability, size and "backward compatibility" with current code.

Regards,

--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com