RE: [HACKERS] SPI_prepare() doesn't work well ?

> -----Original Message-----
> From: Bruce Momjian [mailto:maillist(at)candle(dot)pha(dot)pa(dot)us]
> Sent: Friday, January 22, 1999 1:38 PM
> To: Hiroshi Inoue
> Cc: jwieck(at)debis(dot)com; pgsql-hackers(at)postgreSQL(dot)org
> Subject: Re: [HACKERS] SPI_prepare() doesn't work well ?
>
>
[snip]

> > > >
> > > > 2. Aggregates in PL/pgSQL cause wrong results.
> > > >
[snip]

>
> It is my understanding that this has always been a problem. I have
> never 100% been confident I understand it.
>
> As I remember, there used to be a:
>
> Aggreg **qry_agg
>
> that was a member of the Query structure, and cause all sorts of
> problems because the Agg was in the target list _and_ in the qry_agg.
> That was removed. Looks like I did it, but I don't remember doing it:
>
> revision 1.44
> date: 1998/01/15 19:00:11; author: momjian; state: Exp;
> lines: +2 -4
> Remove Query->qry_aggs and qry_numaggs and replace with
> Query->hasAggs.
>
> Pass List* of Aggregs into executor, and create needed array there.
> No longer need to double-processs Aggregs with second copy in Query.
>
> The removal of that fixed many problems. Can you explain a little more
> on how multiple Agg references happen. Perhaps we can get a good clean
> fix for this. Maybe redesign is needed, as I did for the removal of
> qry_aggs.
>

Sorry,I don't know details.
The source tree I can trace is as follows..

1.Multiple references to Aggreg nodes
[ Fucntion union_planner() in src/backend/optimizer/plan/planner.c ]

if (parse->hasAggs)
{
result_plan = (Plan *) make_agg(tlist, result_plan);

/*
* set the varno/attno entries to the appropriate references
to
* the result tuple of the subplans.
*/
((Agg *) result_plan)->aggs =
set_agg_tlist_references((Agg *) result_plan);

[ Function set_agg_tlist_references() in optimzer/opt/setrefs.c ]

aggreg_list = nconc(
replace_agg_clause(tle->expr, subplanTargetList),
aggreg_list)
;
}
return aggreg_list;

[ Function replace_agg_clause() in optimizer/opt/setrefs.c ]

else if (IsA(clause, Aggreg))
{
return lcons(clause,
^^^^^^^
replace_agg_clause(((Aggreg *) clause)->target,
subplanTargetList));

clause is contained in the return of replace_agg_clause() and so
contained in the return of set_agg_tlist_references().

2.aggno's of aggs list members are set
[ Function ExecAgg() in executor/nodeAgg.c ]

alist = node->aggs;
for (i = 0; i < nagg; i++)
{
aggregates[i] = lfirst(alist);
aggregates[i]->aggno = i;
alist = lnext(alist);
}

3.aggno's are used
[ Function ExecEvalAggreg() in executor/execQual.c
called from ExecEvalExpr() ]

static Datum
ExecEvalAggreg(Aggreg *agg, ExprContext *econtext, bool *isNull)
{
*isNull = econtext->ecxt_nulls[agg->aggno];
return econtext->ecxt_values[agg->aggno];
}

Thanks.

Hiroshi Inoue
Inoue(at)tpf(dot)co(dot)jp