Allow aggregate functions to be VARIADIC.

There's no inherent reason why an aggregate function can't be variadic
(even VARIADIC ANY) if its transition function can handle the case.
Indeed, this patch to add the feature touches none of the planner or
executor, and little of the parser; the main missing stuff was DDL and
pg_dump support.

It is true that variadic aggregates can create the same sort of ambiguity
about parameters versus ORDER BY keys that was complained of when we
(briefly) had both one- and two-argument forms of string_agg().  However,
the policy formed in response to that discussion only said that we'd not
create any built-in aggregates with varying numbers of arguments, not that
we shouldn't allow users to do it.  So the logical extension of that is
we can allow users to make variadic aggregates as long as we're wary about
shipping any such in core.

In passing, this patch allows aggregate function arguments to be named, to
the extent of remembering the names in pg_proc and dumping them in pg_dump.
You can't yet call an aggregate using named-parameter notation.  That seems
like a likely future extension, but it'll take some work, and it's not what
this patch is really about.  Likewise, there's still some work needed to
make window functions handle VARIADIC fully, but I left that for another
day.

initdb forced because of new aggvariadic field in Aggref parse nodes.

1 files changed, 39 insertions, 16 deletions

diff --git a/src/backend/commands/aggregatecmds.c b/src/backend/commands/aggregatecmds.c
index 4a03786210a..78af0924654 100644
--- a/src/backend/commands/aggregatecmds.c
+++ b/src/backend/commands/aggregatecmds.c
@@ -45,10 +45,12 @@
  *
  * "oldstyle" signals the old (pre-8.2) style where the aggregate input type
  * is specified by a BASETYPE element in the parameters.  Otherwise,
- * "args" defines the input type(s).
+ * "args" is a list of FunctionParameter structs defining the agg's arguments.
+ * "parameters" is a list of DefElem representing the agg's definition clauses.
  */
 Oid
-DefineAggregate(List *name, List *args, bool oldstyle, List *parameters)
+DefineAggregate(List *name, List *args, bool oldstyle, List *parameters,
+				const char *queryString)
 {
 	char	   *aggName;
 	Oid			aggNamespace;
@@ -59,8 +61,12 @@ DefineAggregate(List *name, List *args, bool oldstyle, List *parameters)
 	TypeName   *baseType = NULL;
 	TypeName   *transType = NULL;
 	char	   *initval = NULL;
-	Oid		   *aggArgTypes;
 	int			numArgs;
+	oidvector  *parameterTypes;
+	ArrayType  *allParameterTypes;
+	ArrayType  *parameterModes;
+	ArrayType  *parameterNames;
+	List	   *parameterDefaults;
 	Oid			transTypeId;
 	char		transTypeType;
 	ListCell   *pl;
@@ -131,6 +137,8 @@ DefineAggregate(List *name, List *args, bool oldstyle, List *parameters)
 		 * Historically we allowed the command to look like basetype = 'ANY'
 		 * so we must do a case-insensitive comparison for the name ANY. Ugh.
 		 */
+		Oid			aggArgTypes[1];
+
 		if (baseType == NULL)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
@@ -139,22 +147,26 @@ DefineAggregate(List *name, List *args, bool oldstyle, List *parameters)
 		if (pg_strcasecmp(TypeNameToString(baseType), "ANY") == 0)
 		{
 			numArgs = 0;
-			aggArgTypes = NULL;
+			aggArgTypes[0] = InvalidOid;
 		}
 		else
 		{
 			numArgs = 1;
-			aggArgTypes = (Oid *) palloc(sizeof(Oid));
 			aggArgTypes[0] = typenameTypeId(NULL, baseType);
 		}
+		parameterTypes = buildoidvector(aggArgTypes, numArgs);
+		allParameterTypes = NULL;
+		parameterModes = NULL;
+		parameterNames = NULL;
+		parameterDefaults = NIL;
 	}
 	else
 	{
 		/*
-		 * New style: args is a list of TypeNames (possibly zero of 'em).
+		 * New style: args is a list of FunctionParameters (possibly zero of
+		 * 'em).  We share functioncmds.c's code for processing them.
 		 */
-		ListCell   *lc;
-		int			i = 0;
+		Oid			requiredResultType;
 
 		if (baseType != NULL)
 			ereport(ERROR,
@@ -162,13 +174,20 @@ DefineAggregate(List *name, List *args, bool oldstyle, List *parameters)
 					 errmsg("basetype is redundant with aggregate input type specification")));
 
 		numArgs = list_length(args);
-		aggArgTypes = (Oid *) palloc(sizeof(Oid) * numArgs);
-		foreach(lc, args)
-		{
-			TypeName   *curTypeName = (TypeName *) lfirst(lc);
-
-			aggArgTypes[i++] = typenameTypeId(NULL, curTypeName);
-		}
+		interpret_function_parameter_list(args,
+										  InvalidOid,
+										  true, /* is an aggregate */
+										  queryString,
+										  &parameterTypes,
+										  &allParameterTypes,
+										  &parameterModes,
+										  &parameterNames,
+										  &parameterDefaults,
+										  &requiredResultType);
+		/* Parameter defaults are not currently allowed by the grammar */
+		Assert(parameterDefaults == NIL);
+		/* There shouldn't have been any OUT parameters, either */
+		Assert(requiredResultType == InvalidOid);
 	}
 
 	/*
@@ -219,8 +238,12 @@ DefineAggregate(List *name, List *args, bool oldstyle, List *parameters)
 	 */
 	return AggregateCreate(aggName,		/* aggregate name */
 						   aggNamespace,		/* namespace */
-						   aggArgTypes, /* input data type(s) */
 						   numArgs,
+						   parameterTypes,
+						   PointerGetDatum(allParameterTypes),
+						   PointerGetDatum(parameterModes),
+						   PointerGetDatum(parameterNames),
+						   parameterDefaults,
 						   transfuncName,		/* step function name */
 						   finalfuncName,		/* final function name */
 						   sortoperatorName,	/* sort operator name */