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Remove useless entries for aggregate functions from fmgrtab.c.

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Gen_fmgrtab.pl treated aggregate functions the same as other built-in
functions, which is wasteful because there is no real need to have
entries for them in the fmgr_builtins[] table.  Suppressing those
entries saves about 3KB in the compiled table on my machine; which
is not a lot but it's not nothing either, considering that that
table is pretty "hot".  The only outside code change needed is
that ExecInitWindowAgg() can't be allowed to call fmgr_info_cxt()
on a plain aggregate function.  But that saves a few cycles anyway.

Having done that, the aggregate_dummy() function is unreferenced
and might as well be dropped.  Using "aggregate_dummy" as the prosrc
value for an aggregate is now just a documentation convention not
something that matters.  There was some discussion of using NULL
instead to save a few bytes in pg_proc, but we'd have to remove
prosrc's BKI_FORCE_NOT_NULL marking which doesn't seem a great idea.
Anyway, it's possible there's client-side code that expects to
see "aggregate_dummy" there, so I'm loath to change it without a
strong reason.

Discussion: https://postgr.es/m/533989.1604263665@sss.pgh.pa.us
This commit is contained in:
Tom Lane
2020-11-04 11:25:56 -05:00
parent 113d3591b8
commit f21636e5d5
4 changed files with 13 additions and 26 deletions
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10
src/backend/executor/nodeWindowAgg.c
View File

@ -2446,11 +2446,6 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
perfuncstate->wfuncstate = wfuncstate;
perfuncstate->wfunc = wfunc;
perfuncstate->numArguments = list_length(wfuncstate->args);
fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
econtext->ecxt_per_query_memory);
fmgr_info_set_expr((Node *) wfunc, &perfuncstate->flinfo);
perfuncstate->winCollation = wfunc->inputcollid;
get_typlenbyval(wfunc->wintype,
@ -2479,6 +2474,11 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
winobj->argstates = wfuncstate->args;
winobj->localmem = NULL;
perfuncstate->winobj = winobj;
/* It's a real window function, so set up to call it. */
fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
econtext->ecxt_per_query_memory);
fmgr_info_set_expr((Node *) wfunc, &perfuncstate->flinfo);
}
}