Allow omitting one or both boundaries in an array slice specifier.

Omitted boundaries represent the upper or lower limit of the corresponding
array subscript.  This allows simpler specification of many common
use-cases.

(Revised version of commit 9246af6799819847faa33baf441251003acbb8fe)

YUriy Zhuravlev

1 files changed, 31 insertions, 2 deletions

diff --git a/src/backend/utils/adt/arrayfuncs.c b/src/backend/utils/adt/arrayfuncs.c
index 67c9b357c85..359fb1462bc 100644
--- a/src/backend/utils/adt/arrayfuncs.c
+++ b/src/backend/utils/adt/arrayfuncs.c
@@ -1995,6 +1995,8 @@ array_get_element_expanded(Datum arraydatum,
  *	nSubscripts: number of subscripts supplied (must be same for upper/lower)
  *	upperIndx[]: the upper subscript values
  *	lowerIndx[]: the lower subscript values
+ *	upperProvided[]: true for provided upper subscript values
+ *	lowerProvided[]: true for provided lower subscript values
  *	arraytyplen: pg_type.typlen for the array type
  *	elmlen: pg_type.typlen for the array's element type
  *	elmbyval: pg_type.typbyval for the array's element type
@@ -2003,6 +2005,9 @@ array_get_element_expanded(Datum arraydatum,
  * Outputs:
  *	The return value is the new array Datum (it's never NULL)
  *
+ * Omitted upper and lower subscript values are replaced by the corresponding
+ * array bound.
+ *
  * NOTE: we assume it is OK to scribble on the provided subscript arrays
  * lowerIndx[] and upperIndx[].  These are generally just temporaries.
  */
@@ -2011,6 +2016,8 @@ array_get_slice(Datum arraydatum,
 				int nSubscripts,
 				int *upperIndx,
 				int *lowerIndx,
+				bool *upperProvided,
+				bool *lowerProvided,
 				int arraytyplen,
 				int elmlen,
 				bool elmbyval,
@@ -2081,9 +2088,9 @@ array_get_slice(Datum arraydatum,
 
 	for (i = 0; i < nSubscripts; i++)
 	{
-		if (lowerIndx[i] < lb[i])
+		if (!lowerProvided[i] || lowerIndx[i] < lb[i])
 			lowerIndx[i] = lb[i];
-		if (upperIndx[i] >= (dim[i] + lb[i]))
+		if (!upperProvided[i] || upperIndx[i] >= (dim[i] + lb[i]))
 			upperIndx[i] = dim[i] + lb[i] - 1;
 		if (lowerIndx[i] > upperIndx[i])
 			return PointerGetDatum(construct_empty_array(elemtype));
@@ -2708,6 +2715,8 @@ array_set_element_expanded(Datum arraydatum,
  *	nSubscripts: number of subscripts supplied (must be same for upper/lower)
  *	upperIndx[]: the upper subscript values
  *	lowerIndx[]: the lower subscript values
+ *	upperProvided[]: true for provided upper subscript values
+ *	lowerProvided[]: true for provided lower subscript values
  *	srcArrayDatum: the source for the inserted values
  *	isNull: indicates whether srcArrayDatum is NULL
  *	arraytyplen: pg_type.typlen for the array type
@@ -2719,6 +2728,9 @@ array_set_element_expanded(Datum arraydatum,
  *		  A new array is returned, just like the old except for the
  *		  modified range.  The original array object is not changed.
  *
+ * Omitted upper and lower subscript values are replaced by the corresponding
+ * array bound.
+ *
  * For one-dimensional arrays only, we allow the array to be extended
  * by assigning to positions outside the existing subscript range; any
  * positions between the existing elements and the new ones are set to NULLs.
@@ -2735,6 +2747,8 @@ array_set_slice(Datum arraydatum,
 				int nSubscripts,
 				int *upperIndx,
 				int *lowerIndx,
+				bool *upperProvided,
+				bool *lowerProvided,
 				Datum srcArrayDatum,
 				bool isNull,
 				int arraytyplen,
@@ -2806,6 +2820,13 @@ array_set_slice(Datum arraydatum,
 
 		for (i = 0; i < nSubscripts; i++)
 		{
+			if (!upperProvided[i] || !lowerProvided[i])
+				ereport(ERROR,
+						(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
+				errmsg("array slice subscript must provide both boundaries"),
+				errdetail("When assigning to a slice of an empty array value,"
+						  " slice boundaries must be fully specified.")));
+
 			dim[i] = 1 + upperIndx[i] - lowerIndx[i];
 			lb[i] = lowerIndx[i];
 		}
@@ -2839,6 +2860,10 @@ array_set_slice(Datum arraydatum,
 	if (ndim == 1)
 	{
 		Assert(nSubscripts == 1);
+		if (!lowerProvided[0])
+			lowerIndx[0] = lb[0];
+		if (!upperProvided[0])
+			upperIndx[0] = dim[0] + lb[0] - 1;
 		if (lowerIndx[0] > upperIndx[0])
 			ereport(ERROR,
 					(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
@@ -2867,6 +2892,10 @@ array_set_slice(Datum arraydatum,
 		 */
 		for (i = 0; i < nSubscripts; i++)
 		{
+			if (!lowerProvided[i])
+				lowerIndx[i] = lb[i];
+			if (!upperProvided[i])
+				upperIndx[i] = dim[i] + lb[i] - 1;
 			if (lowerIndx[i] > upperIndx[i])
 				ereport(ERROR,
 						(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),