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Support ORDER BY within aggregate function calls, at long last providing a

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non-kluge method for controlling the order in which values are fed to an
aggregate function.  At the same time eliminate the old implementation
restriction that DISTINCT was only supported for single-argument aggregates.

Possibly release-notable behavioral change: formerly, agg(DISTINCT x)
dropped null values of x unconditionally.  Now, it does so only if the
agg transition function is strict; otherwise nulls are treated as DISTINCT
normally would, ie, you get one copy.

Andrew Gierth, reviewed by Hitoshi Harada
This commit is contained in:
Tom Lane
2009-12-15 17:57:48 +00:00
parent 6a6efb9640
commit 34d26872ed
31 changed files with 1184 additions and 248 deletions
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28
src/backend/utils/adt/ruleutils.c
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@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.316 2009/12/07 05:22:22 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.317 2009/12/15 17:57:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -5442,32 +5442,44 @@ get_agg_expr(Aggref *aggref, deparse_context *context)
{
StringInfo buf = context->buf;
Oid argtypes[FUNC_MAX_ARGS];
List *arglist;
int nargs;
ListCell *l;
if (list_length(aggref->args) > FUNC_MAX_ARGS)
ereport(ERROR,
(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
errmsg("too many arguments")));
/* Extract the regular arguments, ignoring resjunk stuff for the moment */
arglist = NIL;
nargs = 0;
foreach(l, aggref->args)
{
Node *arg = (Node *) lfirst(l);
TargetEntry *tle = (TargetEntry *) lfirst(l);
Node *arg = (Node *) tle->expr;
Assert(!IsA(arg, NamedArgExpr));
if (tle->resjunk)
continue;
if (nargs >= FUNC_MAX_ARGS) /* paranoia */
ereport(ERROR,
(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
errmsg("too many arguments")));
argtypes[nargs] = exprType(arg);
arglist = lappend(arglist, arg);
nargs++;
}
appendStringInfo(buf, "%s(%s",
generate_function_name(aggref->aggfnoid, nargs,
NIL, argtypes, NULL),
aggref->aggdistinct ? "DISTINCT " : "");
(aggref->aggdistinct != NIL) ? "DISTINCT " : "");
/* aggstar can be set only in zero-argument aggregates */
if (aggref->aggstar)
appendStringInfoChar(buf, '*');
else
get_rule_expr((Node *) aggref->args, context, true);
get_rule_expr((Node *) arglist, context, true);
if (aggref->aggorder != NIL)
{
appendStringInfoString(buf, " ORDER BY ");
get_rule_orderby(aggref->aggorder, aggref->args, false, context);
}
appendStringInfoChar(buf, ')');
}