Re: Split index and table statistics into different types of stats

On Mon, Nov 21, 2022 at 7:03 PM Drouvot, Bertrand
<bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>
> On 11/21/22 12:19 AM, Andres Freund wrote:
> >
> > That's better, but still seems like quite a bit of repetition, given the
> > number of accessors. I think I like my idea of a macro defining the whole
> > function a bit better.
> >
>
> Got it, what about creating another preparatory commit to first introduce something like:
>
> "
> #define PGSTAT_DEFINE_REL_FIELD_ACCESSOR(function_name_prefix, stat_name) \
> Datum \
> function_name_prefix##_##stat_name(PG_FUNCTION_ARGS) \
> { \
> Oid relid = PG_GETARG_OID(0); \
> int64 result; \
> PgStat_StatTabEntry *tabentry; \
> if ((tabentry = pgstat_fetch_stat_tabentry(relid)) == NULL) \
> result = 0; \
> else \
> result = (int64) (tabentry->stat_name); \
> PG_RETURN_INT64(result); \
> } \
>
> PGSTAT_DEFINE_REL_FIELD_ACCESSOR(pg_stat_get, numscans);
>
> PGSTAT_DEFINE_REL_FIELD_ACCESSOR(pg_stat_get, tuples_returned);
> .
> .
> .
> "
>
> If that makes sense to you, I'll submit this preparatory patch.

I think the macros stitching the function declarations and definitions
is a great idea to avoid code duplicacy. We seem to be using that
approach already - PG_FUNCTION_INFO_V1, SH_DECLARE, SH_DEFINE and its
friends, STEMMER_MODULE and so on. +1 for first applying this
principle for existing functions. Looking forward to the patch.

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