Allow to omit boundaries in array subscript

Allow to omiy lower or upper or both boundaries in array subscript
for selecting slice of array.

Author: YUriy Zhuravlev

1 files changed, 32 insertions, 17 deletions

diff --git a/src/backend/parser/parse_node.c b/src/backend/parser/parse_node.c
index 4130cbff5ed..de6e0b89342 100644
--- a/src/backend/parser/parse_node.c
+++ b/src/backend/parser/parse_node.c
@@ -311,7 +311,7 @@ transformArraySubscripts(ParseState *pstate,
 		elementType = transformArrayType(&arrayType, &arrayTypMod);
 
 	/*
-	 * A list containing only single subscripts refers to a single array
+	 * A list containing only single subscripts (uidx) refers to a single array
 	 * element.  If any of the items are double subscripts (lower:upper), then
 	 * the subscript expression means an array slice operation. In this case,
 	 * we supply a default lower bound of 1 for any items that contain only a
@@ -322,7 +322,7 @@ transformArraySubscripts(ParseState *pstate,
 	{
 		A_Indices  *ai = (A_Indices *) lfirst(idx);
 
-		if (ai->lidx != NULL)
+		if (ai->lidx != NULL || ai->lidx_default)
 		{
 			isSlice = true;
 			break;
@@ -335,9 +335,17 @@ transformArraySubscripts(ParseState *pstate,
 	foreach(idx, indirection)
 	{
 		A_Indices  *ai = (A_Indices *) lfirst(idx);
-		Node	   *subexpr;
+		Node	   *subexpr = NULL;
 
 		Assert(IsA(ai, A_Indices));
+		if ((ai->uidx_default || ai->lidx_default) && assignFrom != NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
+					 errmsg("array subscript must have both boundaries"),
+					 errhint("You can't omit the upper or lower"
+							 " boundaries when updating or inserting"),
+					 parser_errposition(pstate, exprLocation(arrayBase))));
+
 		if (isSlice)
 		{
 			if (ai->lidx)
@@ -356,7 +364,7 @@ transformArraySubscripts(ParseState *pstate,
 							 errmsg("array subscript must have type integer"),
 						parser_errposition(pstate, exprLocation(ai->lidx))));
 			}
-			else
+			else if (ai->lidx_default == false)
 			{
 				/* Make a constant 1 */
 				subexpr = (Node *) makeConst(INT4OID,
@@ -369,19 +377,26 @@ transformArraySubscripts(ParseState *pstate,
 			}
 			lowerIndexpr = lappend(lowerIndexpr, subexpr);
 		}
-		subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
-		/* If it's not int4 already, try to coerce */
-		subexpr = coerce_to_target_type(pstate,
-										subexpr, exprType(subexpr),
-										INT4OID, -1,
-										COERCION_ASSIGNMENT,
-										COERCE_IMPLICIT_CAST,
-										-1);
-		if (subexpr == NULL)
-			ereport(ERROR,
-					(errcode(ERRCODE_DATATYPE_MISMATCH),
-					 errmsg("array subscript must have type integer"),
-					 parser_errposition(pstate, exprLocation(ai->uidx))));
+
+		if (ai->uidx_default == false)
+		{
+			subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
+			/* If it's not int4 already, try to coerce */
+			subexpr = coerce_to_target_type(pstate,
+											subexpr, exprType(subexpr),
+											INT4OID, -1,
+											COERCION_ASSIGNMENT,
+											COERCE_IMPLICIT_CAST,
+											-1);
+			if (subexpr == NULL)
+				ereport(ERROR,
+						(errcode(ERRCODE_DATATYPE_MISMATCH),
+						 errmsg("array subscript must have type integer"),
+						 parser_errposition(pstate, exprLocation(ai->uidx))));
+		}
+		else
+			subexpr = NULL;
+
 		upperIndexpr = lappend(upperIndexpr, subexpr);
 	}