Support UPDATE/DELETE WHERE CURRENT OF cursor_name, per SQL standard.

Along the way, allow FOR UPDATE in non-WITH-HOLD cursors; there may once
have been a reason to disallow that, but it seems to work now, and it's
really rather necessary if you want to select a row via a cursor and then
update it in a concurrent-safe fashion.

Original patch by Arul Shaji, rather heavily editorialized by Tom Lane.

4 files changed, 61 insertions, 4 deletions

diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 39027b1dbc8..c868ff574d9 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -15,7 +15,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.377 2007/06/05 21:31:04 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/copyfuncs.c,v 1.378 2007/06/11 01:16:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1300,6 +1300,20 @@ _copySetToDefault(SetToDefault *from)
 }
 
 /*
+ * _copyCurrentOfExpr
+ */
+static CurrentOfExpr *
+_copyCurrentOfExpr(CurrentOfExpr *from)
+{
+	CurrentOfExpr *newnode = makeNode(CurrentOfExpr);
+
+	COPY_SCALAR_FIELD(cvarno);
+	COPY_STRING_FIELD(cursor_name);
+
+	return newnode;
+}
+
+/*
  * _copyTargetEntry
  */
 static TargetEntry *
@@ -3177,6 +3191,9 @@ copyObject(void *from)
 		case T_SetToDefault:
 			retval = _copySetToDefault(from);
 			break;
+		case T_CurrentOfExpr:
+			retval = _copyCurrentOfExpr(from);
+			break;
 		case T_TargetEntry:
 			retval = _copyTargetEntry(from);
 			break;
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 8a0957c117e..04072c7a654 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -18,7 +18,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.308 2007/06/05 21:31:04 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/equalfuncs.c,v 1.309 2007/06/11 01:16:22 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -599,6 +599,15 @@ _equalSetToDefault(SetToDefault *a, SetToDefault *b)
 }
 
 static bool
+_equalCurrentOfExpr(CurrentOfExpr *a, CurrentOfExpr *b)
+{
+	COMPARE_SCALAR_FIELD(cvarno);
+	COMPARE_STRING_FIELD(cursor_name);
+
+	return true;
+}
+
+static bool
 _equalTargetEntry(TargetEntry *a, TargetEntry *b)
 {
 	COMPARE_NODE_FIELD(expr);
@@ -2124,6 +2133,9 @@ equal(void *a, void *b)
 		case T_SetToDefault:
 			retval = _equalSetToDefault(a, b);
 			break;
+		case T_CurrentOfExpr:
+			retval = _equalCurrentOfExpr(a, b);
+			break;
 		case T_TargetEntry:
 			retval = _equalTargetEntry(a, b);
 			break;
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 5de540642f4..869905f0cc5 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.309 2007/06/05 21:31:04 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/outfuncs.c,v 1.310 2007/06/11 01:16:22 tgl Exp $
  *
  * NOTES
  *	  Every node type that can appear in stored rules' parsetrees *must*
@@ -1059,6 +1059,15 @@ _outSetToDefault(StringInfo str, SetToDefault *node)
 }
 
 static void
+_outCurrentOfExpr(StringInfo str, CurrentOfExpr *node)
+{
+	WRITE_NODE_TYPE("CURRENTOFEXPR");
+
+	WRITE_UINT_FIELD(cvarno);
+	WRITE_STRING_FIELD(cursor_name);
+}
+
+static void
 _outTargetEntry(StringInfo str, TargetEntry *node)
 {
 	WRITE_NODE_TYPE("TARGETENTRY");
@@ -2229,6 +2238,9 @@ _outNode(StringInfo str, void *obj)
 			case T_SetToDefault:
 				_outSetToDefault(str, obj);
 				break;
+			case T_CurrentOfExpr:
+				_outCurrentOfExpr(str, obj);
+				break;
 			case T_TargetEntry:
 				_outTargetEntry(str, obj);
 				break;
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 86c9e911a7c..e91a6e5b501 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/nodes/readfuncs.c,v 1.207 2007/06/05 21:31:04 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/nodes/readfuncs.c,v 1.208 2007/06/11 01:16:22 tgl Exp $
  *
  * NOTES
  *	  Path and Plan nodes do not have any readfuncs support, because we
@@ -874,6 +874,20 @@ _readSetToDefault(void)
 }
 
 /*
+ * _readCurrentOfExpr
+ */
+static CurrentOfExpr *
+_readCurrentOfExpr(void)
+{
+	READ_LOCALS(CurrentOfExpr);
+
+	READ_UINT_FIELD(cvarno);
+	READ_STRING_FIELD(cursor_name);
+
+	READ_DONE();
+}
+
+/*
  * _readTargetEntry
  */
 static TargetEntry *
@@ -1093,6 +1107,8 @@ parseNodeString(void)
 		return_value = _readCoerceToDomainValue();
 	else if (MATCH("SETTODEFAULT", 12))
 		return_value = _readSetToDefault();
+	else if (MATCH("CURRENTOFEXPR", 13))
+		return_value = _readCurrentOfExpr();
 	else if (MATCH("TARGETENTRY", 11))
 		return_value = _readTargetEntry();
 	else if (MATCH("RANGETBLREF", 11))