Support arrays as input to array_agg() and ARRAY(SELECT ...).

These cases formerly failed with errors about "could not find array type
for data type".  Now they yield arrays of the same element type and one
higher dimension.

The implementation involves creating functions with API similar to the
existing accumArrayResult() family.  I (tgl) also extended the base family
by adding an initArrayResult() function, which allows callers to avoid
special-casing the zero-inputs case if they just want an empty array as
result.  (Not all do, so the previous calling convention remains valid.)
This allowed simplifying some existing code in xml.c and plperl.c.

Ali Akbar, reviewed by Pavel Stehule, significantly modified by me

doc/src/sgml/func.sgml

@@ -12035,7 +12035,7 @@ NULL baz</literallayout>(3 rows)</entry>
        <function>array_agg(<replaceable class="parameter">expression</replaceable>)</function>
       </entry>
       <entry>
-       any
+       any non-array type
       </entry>
       <entry>
        array of the argument type
@@ -12043,6 +12043,21 @@ NULL baz</literallayout>(3 rows)</entry>
       <entry>input values, including nulls, concatenated into an array</entry>
      </row>
 
+     <row>
+      <entry>
+       <function>array_agg(<replaceable class="parameter">expression</replaceable>)</function>
+      </entry>
+      <entry>
+       any array type
+      </entry>
+      <entry>
+       same as argument data type
+      </entry>
+      <entry>input arrays concatenated into array of one higher dimension
+       (inputs must all have same dimensionality,
+        and cannot be empty or NULL)</entry>
+     </row>
+
      <row>
       <entry>
        <indexterm>

doc/src/sgml/syntax.sgml

@@ -2239,11 +2239,22 @@ SELECT ARRAY(SELECT oid FROM pg_proc WHERE proname LIKE 'bytea%');
 -----------------------------------------------------------------------
  {2011,1954,1948,1952,1951,1244,1950,2005,1949,1953,2006,31,2412,2413}
 (1 row)
+
+SELECT ARRAY(SELECT ARRAY[i, i*2] FROM generate_series(1,5) AS a(i));
+              array
+----------------------------------
+ {{1,2},{2,4},{3,6},{4,8},{5,10}}
+(1 row)
 </programlisting>
-   The subquery must return a single column. The resulting
+   The subquery must return a single column.
+   If the subquery's output column is of a non-array type, the resulting
    one-dimensional array will have an element for each row in the
    subquery result, with an element type matching that of the
    subquery's output column.
+   If the subquery's output column is of an array type, the result will be
+   an array of the same type but one higher dimension; in this case all
+   the subquery rows must yield arrays of identical dimensionality, else
+   the result would not be rectangular.
   </para>
 
   <para>

doc/src/sgml/xaggr.sgml

@@ -359,12 +359,12 @@ SELECT attrelid::regclass, array_accum(atttypid::regtype)
    aggregate <function>array_agg</> is equivalent to
 
 <programlisting>
-CREATE FUNCTION array_agg_transfn(internal, anyelement)
+CREATE FUNCTION array_agg_transfn(internal, anynonarray)
   RETURNS internal ...;
-CREATE FUNCTION array_agg_finalfn(internal, anyelement)
+CREATE FUNCTION array_agg_finalfn(internal, anynonarray)
   RETURNS anyarray ...;
 
-CREATE AGGREGATE array_agg (anyelement)
+CREATE AGGREGATE array_agg (anynonarray)
 (
     sfunc = array_agg_transfn,
     stype = internal,
@@ -376,7 +376,7 @@ CREATE AGGREGATE array_agg (anyelement)
    Here, the <literal>finalfunc_extra</> option specifies that the final
    function receives, in addition to the state value, extra dummy
    argument(s) corresponding to the aggregate's input argument(s).
-   The extra <type>anyelement</> argument allows the declaration
+   The extra <type>anynonarray</> argument allows the declaration
    of <function>array_agg_finalfn</> to be valid.
   </para>
 

src/backend/executor/nodeSubplan.c

@@ -231,7 +231,7 @@ ExecScanSubPlan(SubPlanState *node,
 	bool		found = false;	/* TRUE if got at least one subplan tuple */
 	ListCell   *pvar;
 	ListCell   *l;
-	ArrayBuildState *astate = NULL;
+	ArrayBuildStateAny *astate = NULL;
 
 	/*
 	 * MULTIEXPR subplans, when "executed", just return NULL; but first we
@@ -259,6 +259,11 @@ ExecScanSubPlan(SubPlanState *node,
 		return (Datum) 0;
 	}
 
+	/* Initialize ArrayBuildStateAny in caller's context, if needed */
+	if (subLinkType == ARRAY_SUBLINK)
+		astate = initArrayResultAny(subplan->firstColType,
+									CurrentMemoryContext);
+
 	/*
 	 * We are probably in a short-lived expression-evaluation context. Switch
 	 * to the per-query context for manipulating the child plan's chgParam,
@@ -366,7 +371,7 @@ ExecScanSubPlan(SubPlanState *node,
 			/* stash away current value */
 			Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 			dvalue = slot_getattr(slot, 1, &disnull);
-			astate = accumArrayResult(astate, dvalue, disnull,
+			astate = accumArrayResultAny(astate, dvalue, disnull,
 										 subplan->firstColType, oldcontext);
 			/* keep scanning subplan to collect all values */
 			continue;
@@ -437,10 +442,7 @@ ExecScanSubPlan(SubPlanState *node,
 	if (subLinkType == ARRAY_SUBLINK)
 	{
 		/* We return the result in the caller's context */
-		if (astate != NULL)
-			result = makeArrayResult(astate, oldcontext);
-		else
-			result = PointerGetDatum(construct_empty_array(subplan->firstColType));
+		result = makeArrayResultAny(astate, oldcontext, true);
 	}
 	else if (!found)
 	{
@@ -951,7 +953,7 @@ ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
 	ListCell   *pvar;
 	ListCell   *l;
 	bool		found = false;
-	ArrayBuildState *astate = NULL;
+	ArrayBuildStateAny *astate = NULL;
 
 	if (subLinkType == ANY_SUBLINK ||
 		subLinkType == ALL_SUBLINK)
@@ -959,6 +961,11 @@ ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
 	if (subLinkType == CTE_SUBLINK)
 		elog(ERROR, "CTE subplans should not be executed via ExecSetParamPlan");
 
+	/* Initialize ArrayBuildStateAny in caller's context, if needed */
+	if (subLinkType == ARRAY_SUBLINK)
+		astate = initArrayResultAny(subplan->firstColType,
+									CurrentMemoryContext);
+
 	/*
 	 * Must switch to per-query memory context.
 	 */
@@ -1018,7 +1025,7 @@ ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
 			/* stash away current value */
 			Assert(subplan->firstColType == tdesc->attrs[0]->atttypid);
 			dvalue = slot_getattr(slot, 1, &disnull);
-			astate = accumArrayResult(astate, dvalue, disnull,
+			astate = accumArrayResultAny(astate, dvalue, disnull,
 										 subplan->firstColType, oldcontext);
 			/* keep scanning subplan to collect all values */
 			continue;
@@ -1072,14 +1079,9 @@ ExecSetParamPlan(SubPlanState *node, ExprContext *econtext)
 		 */
 		if (node->curArray != PointerGetDatum(NULL))
 			pfree(DatumGetPointer(node->curArray));
-		if (astate != NULL)
-			node->curArray = makeArrayResult(astate,
-											 econtext->ecxt_per_query_memory);
-		else
-		{
-			MemoryContextSwitchTo(econtext->ecxt_per_query_memory);
-			node->curArray = PointerGetDatum(construct_empty_array(subplan->firstColType));
-		}
+		node->curArray = makeArrayResultAny(astate,
+											econtext->ecxt_per_query_memory,
+											true);
 		prm->execPlan = NULL;
 		prm->value = node->curArray;
 		prm->isnull = false;

src/backend/nodes/nodeFuncs.c

@@ -108,7 +108,7 @@ exprType(const Node *expr)
 					type = exprType((Node *) tent->expr);
 					if (sublink->subLinkType == ARRAY_SUBLINK)
 					{
-						type = get_array_type(type);
+						type = get_promoted_array_type(type);
 						if (!OidIsValid(type))
 							ereport(ERROR,
 									(errcode(ERRCODE_UNDEFINED_OBJECT),
@@ -139,7 +139,7 @@ exprType(const Node *expr)
 					type = subplan->firstColType;
 					if (subplan->subLinkType == ARRAY_SUBLINK)
 					{
-						type = get_array_type(type);
+						type = get_promoted_array_type(type);
 						if (!OidIsValid(type))
 							ereport(ERROR,
 									(errcode(ERRCODE_UNDEFINED_OBJECT),

src/backend/optimizer/plan/subselect.c

@@ -668,7 +668,7 @@ build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
 
 		Assert(!te->resjunk);
 		Assert(testexpr == NULL);
-		arraytype = get_array_type(exprType((Node *) te->expr));
+		arraytype = get_promoted_array_type(exprType((Node *) te->expr));
 		if (!OidIsValid(arraytype))
 			elog(ERROR, "could not find array type for datatype %s",
 				 format_type_be(exprType((Node *) te->expr)));

src/backend/utils/adt/array_userfuncs.c

@@ -471,7 +471,7 @@ create_singleton_array(FunctionCallInfo fcinfo,
 
 
 /*
- * ARRAY_AGG aggregate function
+ * ARRAY_AGG(anynonarray) aggregate function
  */
 Datum
 array_agg_transfn(PG_FUNCTION_ARGS)
@@ -486,6 +486,12 @@ array_agg_transfn(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("could not determine input data type")));
 
+	/*
+	 * Note: we do not need a run-time check about whether arg1_typeid is a
+	 * valid array element type, because the parser would have verified that
+	 * while resolving the input/result types of this polymorphic aggregate.
+	 */
+
 	if (!AggCheckCallContext(fcinfo, &aggcontext))
 	{
 		/* cannot be called directly because of internal-type argument */
@@ -516,18 +522,13 @@ array_agg_finalfn(PG_FUNCTION_ARGS)
 	int			dims[1];
 	int			lbs[1];
 
-	/*
-	 * Test for null before Asserting we are in right context.  This is to
-	 * avoid possible Assert failure in 8.4beta installations, where it is
-	 * possible for users to create NULL constants of type internal.
-	 */
-	if (PG_ARGISNULL(0))
-		PG_RETURN_NULL();		/* returns null iff no input values */
-
 	/* cannot be called directly because of internal-type argument */
 	Assert(AggCheckCallContext(fcinfo, NULL));
 
-	state = (ArrayBuildState *) PG_GETARG_POINTER(0);
+	state = PG_ARGISNULL(0) ? NULL : (ArrayBuildState *) PG_GETARG_POINTER(0);
+
+	if (state == NULL)
+		PG_RETURN_NULL();		/* returns null iff no input values */
 
 	dims[0] = state->nelems;
 	lbs[0] = 1;
@@ -544,3 +545,70 @@ array_agg_finalfn(PG_FUNCTION_ARGS)
 
 	PG_RETURN_DATUM(result);
 }
+
+/*
+ * ARRAY_AGG(anyarray) aggregate function
+ */
+Datum
+array_agg_array_transfn(PG_FUNCTION_ARGS)
+{
+	Oid			arg1_typeid = get_fn_expr_argtype(fcinfo->flinfo, 1);
+	MemoryContext aggcontext;
+	ArrayBuildStateArr *state;
+
+	if (arg1_typeid == InvalidOid)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("could not determine input data type")));
+
+	/*
+	 * Note: we do not need a run-time check about whether arg1_typeid is a
+	 * valid array type, because the parser would have verified that while
+	 * resolving the input/result types of this polymorphic aggregate.
+	 */
+
+	if (!AggCheckCallContext(fcinfo, &aggcontext))
+	{
+		/* cannot be called directly because of internal-type argument */
+		elog(ERROR, "array_agg_array_transfn called in non-aggregate context");
+	}
+
+	state = PG_ARGISNULL(0) ? NULL : (ArrayBuildStateArr *) PG_GETARG_POINTER(0);
+	state = accumArrayResultArr(state,
+								PG_GETARG_DATUM(1),
+								PG_ARGISNULL(1),
+								arg1_typeid,
+								aggcontext);
+
+	/*
+	 * The transition type for array_agg() is declared to be "internal", which
+	 * is a pass-by-value type the same size as a pointer.  So we can safely
+	 * pass the ArrayBuildStateArr pointer through nodeAgg.c's machinations.
+	 */
+	PG_RETURN_POINTER(state);
+}
+
+Datum
+array_agg_array_finalfn(PG_FUNCTION_ARGS)
+{
+	Datum		result;
+	ArrayBuildStateArr *state;
+
+	/* cannot be called directly because of internal-type argument */
+	Assert(AggCheckCallContext(fcinfo, NULL));
+
+	state = PG_ARGISNULL(0) ? NULL : (ArrayBuildStateArr *) PG_GETARG_POINTER(0);
+
+	if (state == NULL)
+		PG_RETURN_NULL();		/* returns null iff no input values */
+
+	/*
+	 * Make the result.  We cannot release the ArrayBuildStateArr because
+	 * sometimes aggregate final functions are re-executed.  Rather, it is
+	 * nodeAgg.c's responsibility to reset the aggcontext when it's safe to do
+	 * so.
+	 */
+	result = makeArrayResultArr(state, CurrentMemoryContext, false);
+
+	PG_RETURN_DATUM(result);
+}

src/backend/utils/adt/xml.c

@@ -143,7 +143,7 @@ static xmlDocPtr xml_parse(text *data, XmlOptionType xmloption_arg,
 		  bool preserve_whitespace, int encoding);
 static text *xml_xmlnodetoxmltype(xmlNodePtr cur);
 static int xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
-					   ArrayBuildState **astate);
+					   ArrayBuildState *astate);
 #endif   /* USE_LIBXML */
 
 static StringInfo query_to_xml_internal(const char *query, char *tablename,
@@ -3648,7 +3648,7 @@ xml_xmlnodetoxmltype(xmlNodePtr cur)
 
 /*
  * Convert an XML XPath object (the result of evaluating an XPath expression)
- * to an array of xml values, which is returned at *astate.  The function
+ * to an array of xml values, which are appended to astate.  The function
  * result value is the number of elements in the array.
  *
  * If "astate" is NULL then we don't generate the array value, but we still
@@ -3660,16 +3660,13 @@ xml_xmlnodetoxmltype(xmlNodePtr cur)
  */
 static int
 xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
-					   ArrayBuildState **astate)
+					   ArrayBuildState *astate)
 {
 	int			result = 0;
 	Datum		datum;
 	Oid			datumtype;
 	char	   *result_str;
 
-	if (astate != NULL)
-		*astate = NULL;
-
 	switch (xpathobj->type)
 	{
 		case XPATH_NODESET:
@@ -3683,9 +3680,8 @@ xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
 					for (i = 0; i < result; i++)
 					{
 						datum = PointerGetDatum(xml_xmlnodetoxmltype(xpathobj->nodesetval->nodeTab[i]));
-						*astate = accumArrayResult(*astate, datum,
-												   false, XMLOID,
-												   CurrentMemoryContext);
+						(void) accumArrayResult(astate, datum, false,
+												XMLOID, CurrentMemoryContext);
 					}
 				}
 			}
@@ -3721,9 +3717,8 @@ xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
 	/* Common code for scalar-value cases */
 	result_str = map_sql_value_to_xml_value(datum, datumtype, true);
 	datum = PointerGetDatum(cstring_to_xmltype(result_str));
-	*astate = accumArrayResult(*astate, datum,
-							   false, XMLOID,
-							   CurrentMemoryContext);
+	(void) accumArrayResult(astate, datum, false,
+							XMLOID, CurrentMemoryContext);
 	return 1;
 }
 
@@ -3741,7 +3736,7 @@ xml_xpathobjtoxmlarray(xmlXPathObjectPtr xpathobj,
  */
 static void
 xpath_internal(text *xpath_expr_text, xmltype *data, ArrayType *namespaces,
-			   int *res_nitems, ArrayBuildState **astate)
+			   int *res_nitems, ArrayBuildState *astate)
 {
 	PgXmlErrorContext *xmlerrcxt;
 	volatile xmlParserCtxtPtr ctxt = NULL;
@@ -3933,15 +3928,11 @@ xpath(PG_FUNCTION_ARGS)
 	text	   *xpath_expr_text = PG_GETARG_TEXT_P(0);
 	xmltype    *data = PG_GETARG_XML_P(1);
 	ArrayType  *namespaces = PG_GETARG_ARRAYTYPE_P(2);
-	int			res_nitems;
 	ArrayBuildState *astate;
 
+	astate = initArrayResult(XMLOID, CurrentMemoryContext);
 	xpath_internal(xpath_expr_text, data, namespaces,
-				   &res_nitems, &astate);
-
-	if (res_nitems == 0)
-		PG_RETURN_ARRAYTYPE_P(construct_empty_array(XMLOID));
-	else
+				   NULL, astate);
 	PG_RETURN_ARRAYTYPE_P(makeArrayResult(astate, CurrentMemoryContext));
 #else
 	NO_XML_SUPPORT();

src/backend/utils/cache/lsyscache.c

@@ -2354,6 +2354,27 @@ get_array_type(Oid typid)
 	return result;
 }
 
+/*
+ * get_promoted_array_type
+ *
+ *		The "promoted" type is what you'd get from an ARRAY(SELECT ...)
+ *		construct, that is, either the corresponding "true" array type
+ *		if the input is a scalar type that has such an array type,
+ *		or the same type if the input is already a "true" array type.
+ *		Returns InvalidOid if neither rule is satisfied.
+ */
+Oid
+get_promoted_array_type(Oid typid)
+{
+	Oid			array_type = get_array_type(typid);
+
+	if (OidIsValid(array_type))
+		return array_type;
+	if (OidIsValid(get_element_type(typid)))
+		return typid;
+	return InvalidOid;
+}
+
 /*
  * get_base_element_type
  *		Given the type OID, get the typelem, looking "through" any domain

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201411111
+#define CATALOG_VERSION_NO	201411251
 
 #endif

src/include/catalog/pg_aggregate.h

@@ -275,6 +275,7 @@ DATA(insert ( 2901	n 0 xmlconcat2	-					-				-				-				f f 0	142		0	0		0	_null_
 
 /* array */
 DATA(insert ( 2335	n 0 array_agg_transfn	array_agg_finalfn	-				-				-				t f 0	2281	0	0		0	_null_ _null_ ));
+DATA(insert ( 4053	n 0 array_agg_array_transfn array_agg_array_finalfn -		-				-				t f 0	2281	0	0		0	_null_ _null_ ));
 
 /* text */
 DATA(insert ( 3538	n 0 string_agg_transfn	string_agg_finalfn	-				-				-				f f 0	2281	0	0		0	_null_ _null_ ));

src/include/catalog/pg_proc.h

@@ -908,11 +908,17 @@ DATA(insert OID = 3167 (  array_remove	   PGNSP PGUID 12 1 0 0 0 f f f f f f i 2
 DESCR("remove any occurrences of an element from an array");
 DATA(insert OID = 3168 (  array_replace    PGNSP PGUID 12 1 0 0 0 f f f f f f i 3 0 2277 "2277 2283 2283" _null_ _null_ _null_ _null_ array_replace _null_ _null_ _null_ ));
 DESCR("replace any occurrences of an element in an array");
-DATA(insert OID = 2333 (  array_agg_transfn   PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2281 "2281 2283" _null_ _null_ _null_ _null_ array_agg_transfn _null_ _null_ _null_ ));
+DATA(insert OID = 2333 (  array_agg_transfn   PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2281 "2281 2776" _null_ _null_ _null_ _null_ array_agg_transfn _null_ _null_ _null_ ));
 DESCR("aggregate transition function");
-DATA(insert OID = 2334 (  array_agg_finalfn   PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2277 "2281 2283" _null_ _null_ _null_ _null_ array_agg_finalfn _null_ _null_ _null_ ));
+DATA(insert OID = 2334 (  array_agg_finalfn   PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2277 "2281 2776" _null_ _null_ _null_ _null_ array_agg_finalfn _null_ _null_ _null_ ));
 DESCR("aggregate final function");
-DATA(insert OID = 2335 (  array_agg		   PGNSP PGUID 12 1 0 0 0 t f f f f f i 1 0 2277 "2283" _null_ _null_ _null_ _null_ aggregate_dummy _null_ _null_ _null_ ));
+DATA(insert OID = 2335 (  array_agg		   PGNSP PGUID 12 1 0 0 0 t f f f f f i 1 0 2277 "2776" _null_ _null_ _null_ _null_ aggregate_dummy _null_ _null_ _null_ ));
+DESCR("concatenate aggregate input into an array");
+DATA(insert OID = 4051 (  array_agg_array_transfn	PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2281 "2281 2277" _null_ _null_ _null_ _null_ array_agg_array_transfn _null_ _null_ _null_ ));
+DESCR("aggregate transition function");
+DATA(insert OID = 4052 (  array_agg_array_finalfn	PGNSP PGUID 12 1 0 0 0 f f f f f f i 2 0 2277 "2281 2277" _null_ _null_ _null_ _null_ array_agg_array_finalfn _null_ _null_ _null_ ));
+DESCR("aggregate final function");
+DATA(insert OID = 4053 (  array_agg		   PGNSP PGUID 12 1 0 0 0 t f f f f f i 1 0 2277 "2277" _null_ _null_ _null_ _null_ aggregate_dummy _null_ _null_ _null_ ));
 DESCR("concatenate aggregate input into an array");
 DATA(insert OID = 3218 ( width_bucket	   PGNSP PGUID 12 1 0 0 0 f f f f t f i 2 0 23 "2283 2277" _null_ _null_ _null_ _null_ width_bucket_array _null_ _null_ _null_ ));
 DESCR("bucket number of operand given a sorted array of bucket lower bounds");

src/include/utils/array.h

@@ -76,6 +76,7 @@ typedef struct
 
 /*
  * working state for accumArrayResult() and friends
+ * note that the input must be scalars (legal array elements)
  */
 typedef struct ArrayBuildState
 {
@@ -90,6 +91,37 @@ typedef struct ArrayBuildState
 	char		typalign;
 } ArrayBuildState;
 
+/*
+ * working state for accumArrayResultArr() and friends
+ * note that the input must be arrays, and the same array type is returned
+ */
+typedef struct ArrayBuildStateArr
+{
+	MemoryContext mcontext;		/* where all the temp stuff is kept */
+	char	   *data;			/* accumulated data */
+	bits8	   *nullbitmap;		/* bitmap of is-null flags, or NULL if none */
+	int			abytes;			/* allocated length of "data" */
+	int			nbytes;			/* number of bytes used so far */
+	int			aitems;			/* allocated length of bitmap (in elements) */
+	int			nitems;			/* total number of elements in result */
+	int			ndims;			/* current dimensions of result */
+	int			dims[MAXDIM];
+	int			lbs[MAXDIM];
+	Oid			array_type;		/* data type of the arrays */
+	Oid			element_type;	/* data type of the array elements */
+} ArrayBuildStateArr;
+
+/*
+ * working state for accumArrayResultAny() and friends
+ * these functions handle both cases
+ */
+typedef struct ArrayBuildStateAny
+{
+	/* Exactly one of these is not NULL: */
+	ArrayBuildState *scalarstate;
+	ArrayBuildStateArr *arraystate;
+} ArrayBuildStateAny;
+
 /*
  * structure to cache type metadata needed for array manipulation
  */
@@ -252,6 +284,9 @@ extern void deconstruct_array(ArrayType *array,
 				  int elmlen, bool elmbyval, char elmalign,
 				  Datum **elemsp, bool **nullsp, int *nelemsp);
 extern bool array_contains_nulls(ArrayType *array);
+
+extern ArrayBuildState *initArrayResult(Oid element_type,
+				MemoryContext rcontext);
 extern ArrayBuildState *accumArrayResult(ArrayBuildState *astate,
 				 Datum dvalue, bool disnull,
 				 Oid element_type,
@@ -261,6 +296,24 @@ extern Datum makeArrayResult(ArrayBuildState *astate,
 extern Datum makeMdArrayResult(ArrayBuildState *astate, int ndims,
 				  int *dims, int *lbs, MemoryContext rcontext, bool release);
 
+extern ArrayBuildStateArr *initArrayResultArr(Oid array_type, Oid element_type,
+				   MemoryContext rcontext);
+extern ArrayBuildStateArr *accumArrayResultArr(ArrayBuildStateArr *astate,
+					Datum dvalue, bool disnull,
+					Oid array_type,
+					MemoryContext rcontext);
+extern Datum makeArrayResultArr(ArrayBuildStateArr *astate,
+				   MemoryContext rcontext, bool release);
+
+extern ArrayBuildStateAny *initArrayResultAny(Oid input_type,
+				   MemoryContext rcontext);
+extern ArrayBuildStateAny *accumArrayResultAny(ArrayBuildStateAny *astate,
+					Datum dvalue, bool disnull,
+					Oid input_type,
+					MemoryContext rcontext);
+extern Datum makeArrayResultAny(ArrayBuildStateAny *astate,
+				   MemoryContext rcontext, bool release);
+
 extern ArrayIterator array_create_iterator(ArrayType *arr, int slice_ndim);
 extern bool array_iterate(ArrayIterator iterator, Datum *value, bool *isnull);
 extern void array_free_iterator(ArrayIterator iterator);
@@ -292,6 +345,8 @@ extern ArrayType *create_singleton_array(FunctionCallInfo fcinfo,
 
 extern Datum array_agg_transfn(PG_FUNCTION_ARGS);
 extern Datum array_agg_finalfn(PG_FUNCTION_ARGS);
+extern Datum array_agg_array_transfn(PG_FUNCTION_ARGS);
+extern Datum array_agg_array_finalfn(PG_FUNCTION_ARGS);
 
 /*
  * prototypes for functions defined in array_typanalyze.c

src/include/utils/lsyscache.h

@@ -128,6 +128,7 @@ extern void get_type_category_preferred(Oid typid,
 extern Oid	get_typ_typrelid(Oid typid);
 extern Oid	get_element_type(Oid typid);
 extern Oid	get_array_type(Oid typid);
+extern Oid	get_promoted_array_type(Oid typid);
 extern Oid	get_base_element_type(Oid typid);
 extern void getTypeInputInfo(Oid type, Oid *typInput, Oid *typIOParam);
 extern void getTypeOutputInfo(Oid type, Oid *typOutput, bool *typIsVarlena);

src/pl/plperl/plperl.c

@@ -268,7 +268,7 @@ static Datum plperl_sv_to_datum(SV *sv, Oid typid, int32 typmod,
 				   bool *isnull);
 static void _sv_to_datum_finfo(Oid typid, FmgrInfo *finfo, Oid *typioparam);
 static Datum plperl_array_to_datum(SV *src, Oid typid, int32 typmod);
-static ArrayBuildState *array_to_datum_internal(AV *av, ArrayBuildState *astate,
+static void array_to_datum_internal(AV *av, ArrayBuildState *astate,
 						int *ndims, int *dims, int cur_depth,
 						Oid arraytypid, Oid elemtypid, int32 typmod,
 						FmgrInfo *finfo, Oid typioparam);
@@ -1127,7 +1127,7 @@ get_perl_array_ref(SV *sv)
 /*
  * helper function for plperl_array_to_datum, recurses for multi-D arrays
  */
-static ArrayBuildState *
+static void
 array_to_datum_internal(AV *av, ArrayBuildState *astate,
 						int *ndims, int *dims, int cur_depth,
 						Oid arraytypid, Oid elemtypid, int32 typmod,
@@ -1168,7 +1168,7 @@ array_to_datum_internal(AV *av, ArrayBuildState *astate,
 						 errmsg("multidimensional arrays must have array expressions with matching dimensions")));
 
 			/* recurse to fetch elements of this sub-array */
-			astate = array_to_datum_internal(nav, astate,
+			array_to_datum_internal(nav, astate,
 									ndims, dims, cur_depth + 1,
 									arraytypid, elemtypid, typmod,
 									finfo, typioparam);
@@ -1192,12 +1192,10 @@ array_to_datum_internal(AV *av, ArrayBuildState *astate,
 									 typioparam,
 									 &isnull);
 
-			astate = accumArrayResult(astate, dat, isnull,
+			(void) accumArrayResult(astate, dat, isnull,
 									elemtypid, CurrentMemoryContext);
 		}
 	}
-
-	return astate;
 }
 
 /*
@@ -1222,18 +1220,21 @@ plperl_array_to_datum(SV *src, Oid typid, int32 typmod)
 				 errmsg("cannot convert Perl array to non-array type %s",
 						format_type_be(typid))));
 
+	astate = initArrayResult(elemtypid, CurrentMemoryContext);
+
 	_sv_to_datum_finfo(elemtypid, &finfo, &typioparam);
 
 	memset(dims, 0, sizeof(dims));
 	dims[0] = av_len((AV *) SvRV(src)) + 1;
 
-	astate = array_to_datum_internal((AV *) SvRV(src), NULL,
+	array_to_datum_internal((AV *) SvRV(src), astate,
 							&ndims, dims, 1,
 							typid, elemtypid, typmod,
 							&finfo, typioparam);
 
-	if (!astate)
-		return PointerGetDatum(construct_empty_array(elemtypid));
+	/* ensure we get zero-D array for no inputs, as per PG convention */
+	if (dims[0] <= 0)
+		ndims = 0;
 
 	for (i = 0; i < ndims; i++)
 		lbs[i] = 1;

src/test/regress/expected/arrays.out

@@ -1497,6 +1497,7 @@ select cardinality('{{{1,9},{5,6}},{{2,3},{3,4}}}'::int[]);
            8
 (1 row)
 
+-- array_agg(anynonarray)
 select array_agg(unique1) from (select unique1 from tenk1 where unique1 < 15 order by unique1) ss;
               array_agg               
 --------------------------------------
@@ -1521,6 +1522,55 @@ select array_agg(unique1) from tenk1 where unique1 < -15;
  
 (1 row)
 
+-- array_agg(anyarray)
+select array_agg(ar)
+  from (values ('{1,2}'::int[]), ('{3,4}'::int[])) v(ar);
+   array_agg   
+---------------
+ {{1,2},{3,4}}
+(1 row)
+
+select array_agg(distinct ar order by ar desc)
+  from (select array[i / 2] from generate_series(1,10) a(i)) b(ar);
+         array_agg         
+---------------------------
+ {{5},{4},{3},{2},{1},{0}}
+(1 row)
+
+select array_agg(ar)
+  from (select array_agg(array[i, i+1, i-1])
+        from generate_series(1,2) a(i)) b(ar);
+      array_agg      
+---------------------
+ {{{1,2,0},{2,3,1}}}
+(1 row)
+
+select array_agg(array[i+1.2, i+1.3, i+1.4]) from generate_series(1,3) g(i);
+                  array_agg                  
+---------------------------------------------
+ {{2.2,2.3,2.4},{3.2,3.3,3.4},{4.2,4.3,4.4}}
+(1 row)
+
+select array_agg(array['Hello', i::text]) from generate_series(9,11) g(i);
+             array_agg             
+-----------------------------------
+ {{Hello,9},{Hello,10},{Hello,11}}
+(1 row)
+
+select array_agg(array[i, nullif(i, 3), i+1]) from generate_series(1,4) g(i);
+              array_agg               
+--------------------------------------
+ {{1,1,2},{2,2,3},{3,NULL,4},{4,4,5}}
+(1 row)
+
+-- errors
+select array_agg('{}'::int[]) from generate_series(1,2);
+ERROR:  cannot accumulate empty arrays
+select array_agg(null::int[]) from generate_series(1,2);
+ERROR:  cannot accumulate null arrays
+select array_agg(ar)
+  from (values ('{1,2}'::int[]), ('{3}'::int[])) v(ar);
+ERROR:  cannot accumulate arrays of different dimensionality
 select unnest(array[1,2,3]);
  unnest 
 --------
@@ -1660,6 +1710,19 @@ select array_replace(array['AB',NULL,'CDE'],NULL,'12');
  {AB,12,CDE}
 (1 row)
 
+-- array(select array-value ...)
+select array(select array[i,i/2] from generate_series(1,5) i);
+              array              
+---------------------------------
+ {{1,0},{2,1},{3,1},{4,2},{5,2}}
+(1 row)
+
+select array(select array['Hello', i::text] from generate_series(9,11) i);
+               array               
+-----------------------------------
+ {{Hello,9},{Hello,10},{Hello,11}}
+(1 row)
+
 -- Insert/update on a column that is array of composite
 create temp table t1 (f1 int8_tbl[]);
 insert into t1 (f1[5].q1) values(42);

src/test/regress/sql/arrays.sql

@@ -427,11 +427,29 @@ select cardinality('{{1,2}}'::int[]);
 select cardinality('{{1,2},{3,4},{5,6}}'::int[]);
 select cardinality('{{{1,9},{5,6}},{{2,3},{3,4}}}'::int[]);
 
+-- array_agg(anynonarray)
 select array_agg(unique1) from (select unique1 from tenk1 where unique1 < 15 order by unique1) ss;
 select array_agg(ten) from (select ten from tenk1 where unique1 < 15 order by unique1) ss;
 select array_agg(nullif(ten, 4)) from (select ten from tenk1 where unique1 < 15 order by unique1) ss;
 select array_agg(unique1) from tenk1 where unique1 < -15;
 
+-- array_agg(anyarray)
+select array_agg(ar)
+  from (values ('{1,2}'::int[]), ('{3,4}'::int[])) v(ar);
+select array_agg(distinct ar order by ar desc)
+  from (select array[i / 2] from generate_series(1,10) a(i)) b(ar);
+select array_agg(ar)
+  from (select array_agg(array[i, i+1, i-1])
+        from generate_series(1,2) a(i)) b(ar);
+select array_agg(array[i+1.2, i+1.3, i+1.4]) from generate_series(1,3) g(i);
+select array_agg(array['Hello', i::text]) from generate_series(9,11) g(i);
+select array_agg(array[i, nullif(i, 3), i+1]) from generate_series(1,4) g(i);
+-- errors
+select array_agg('{}'::int[]) from generate_series(1,2);
+select array_agg(null::int[]) from generate_series(1,2);
+select array_agg(ar)
+  from (values ('{1,2}'::int[]), ('{3}'::int[])) v(ar);
+
 select unnest(array[1,2,3]);
 select * from unnest(array[1,2,3]);
 select unnest(array[1,2,3,4.5]::float8[]);
@@ -452,6 +470,10 @@ select array_replace(array['A','B','DD','B'],'B','CC');
 select array_replace(array[1,NULL,3],NULL,NULL);
 select array_replace(array['AB',NULL,'CDE'],NULL,'12');
 
+-- array(select array-value ...)
+select array(select array[i,i/2] from generate_series(1,5) i);
+select array(select array['Hello', i::text] from generate_series(9,11) i);
+
 -- Insert/update on a column that is array of composite
 
 create temp table t1 (f1 int8_tbl[]);