From fc8c5fbf5d7763b070f50b1afa85c7f955a83d77 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 6 Nov 2006 18:21:47 +0000
Subject: Repair bug #2694 concerning an ARRAY[] construct whose inputs are
 empty sub-arrays.  Per discussion, if all inputs are empty arrays then result
 must be an empty array too, whereas a mix of empty and nonempty arrays should
 (and already did) draw an error.  In the back branches, the construct was
 strict: any NULL input immediately yielded a NULL output; so I left that
 behavior alone.  HEAD was simply ignoring NULL sub-arrays, which doesn't seem
 very sensible.  For lack of a better idea it now treats NULL sub-arrays the
 same as empty ones.

---
 src/backend/executor/execQual.c | 39 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/src/backend/executor/execQual.c b/src/backend/executor/execQual.c
index 5ff95e1087..91271423b0 100644
--- a/src/backend/executor/execQual.c
+++ b/src/backend/executor/execQual.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.171.4.1 2005/10/19 22:51:26 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.171.4.2 2006/11/06 18:21:47 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2170,6 +2170,7 @@ ExecEvalArray(ArrayExprState *astate, ExprContext *econtext,
 		int		   *elem_dims = NULL;
 		int		   *elem_lbs = NULL;
 		bool		firstone = true;
+		bool		haveempty = false;
 		int			i;
 
 		/* loop through and get data area from each element */
@@ -2179,6 +2180,7 @@ ExecEvalArray(ArrayExprState *astate, ExprContext *econtext,
 			bool		eisnull;
 			Datum		arraydatum;
 			ArrayType  *array;
+			int			this_ndims;
 			int			elem_ndatabytes;
 
 			arraydatum = ExecEvalExpr(e, econtext, &eisnull, NULL);
@@ -2200,10 +2202,18 @@ ExecEvalArray(ArrayExprState *astate, ExprContext *econtext,
 								   format_type_be(ARR_ELEMTYPE(array)),
 								   format_type_be(element_type))));
 
+			this_ndims = ARR_NDIM(array);
+			/* temporarily ignore zero-dimensional subarrays */
+			if (this_ndims <= 0)
+			{
+				haveempty = true;
+				continue;
+			}
+
 			if (firstone)
 			{
 				/* Get sub-array details from first member */
-				elem_ndims = ARR_NDIM(array);
+				elem_ndims = this_ndims;
 				ndims = elem_ndims + 1;
 				if (ndims <= 0 || ndims > MAXDIM)
 					ereport(ERROR,
@@ -2221,7 +2231,7 @@ ExecEvalArray(ArrayExprState *astate, ExprContext *econtext,
 			else
 			{
 				/* Check other sub-arrays are compatible */
-				if (elem_ndims != ARR_NDIM(array) ||
+				if (elem_ndims != this_ndims ||
 					memcmp(elem_dims, ARR_DIMS(array),
 						   elem_ndims * sizeof(int)) != 0 ||
 					memcmp(elem_lbs, ARR_LBOUND(array),
@@ -2244,6 +2254,29 @@ ExecEvalArray(ArrayExprState *astate, ExprContext *econtext,
 				   elem_ndatabytes);
 		}
 
+		/*
+		 * If all items were empty arrays, return an empty array;
+		 * otherwise, if some were and some weren't, raise error.  (Note:
+		 * we must special-case this somehow to avoid trying to generate
+		 * a 1-D array formed from empty arrays.  It's not ideal...)
+		 */
+		if (haveempty)
+		{
+			if (ndims == 0)		/* didn't find any nonempty array */
+			{
+				result = (ArrayType *) palloc(sizeof(ArrayType));
+				result->size = sizeof(ArrayType);
+				result->ndim = 0;
+				result->flags = 0;
+				result->elemtype = element_type;
+				return PointerGetDatum(result);
+			}
+			ereport(ERROR,
+					(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
+					 errmsg("multidimensional arrays must have array "
+							"expressions with matching dimensions")));
+		}
+
 		/* setup for multi-D array */
 		dims[0] = outer_nelems;
 		lbs[0] = 1;
-- 
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