Support MergeAppend plans, to allow sorted output from append relations.

This patch eliminates the former need to sort the output of an Append scan
when an ordered scan of an inheritance tree is wanted.  This should be
particularly useful for fast-start cases such as queries with LIMIT.

Original patch by Greg Stark, with further hacking by Hans-Jurgen Schonig,
Robert Haas, and Tom Lane.

1 files changed, 42 insertions, 0 deletions

diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 55665ca20e5..ee2aeb0ad30 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -345,6 +345,32 @@ _outAppend(StringInfo str, Append *node)
 }
 
 static void
+_outMergeAppend(StringInfo str, MergeAppend *node)
+{
+	int			i;
+
+	WRITE_NODE_TYPE("MERGEAPPEND");
+
+	_outPlanInfo(str, (Plan *) node);
+
+	WRITE_NODE_FIELD(mergeplans);
+
+	WRITE_INT_FIELD(numCols);
+
+	appendStringInfo(str, " :sortColIdx");
+	for (i = 0; i < node->numCols; i++)
+		appendStringInfo(str, " %d", node->sortColIdx[i]);
+
+	appendStringInfo(str, " :sortOperators");
+	for (i = 0; i < node->numCols; i++)
+		appendStringInfo(str, " %u", node->sortOperators[i]);
+
+	appendStringInfo(str, " :nullsFirst");
+	for (i = 0; i < node->numCols; i++)
+		appendStringInfo(str, " %s", booltostr(node->nullsFirst[i]));
+}
+
+static void
 _outRecursiveUnion(StringInfo str, RecursiveUnion *node)
 {
 	int			i;
@@ -1460,6 +1486,16 @@ _outAppendPath(StringInfo str, AppendPath *node)
 }
 
 static void
+_outMergeAppendPath(StringInfo str, MergeAppendPath *node)
+{
+	WRITE_NODE_TYPE("MERGEAPPENDPATH");
+
+	_outPathInfo(str, (Path *) node);
+
+	WRITE_NODE_FIELD(subpaths);
+}
+
+static void
 _outResultPath(StringInfo str, ResultPath *node)
 {
 	WRITE_NODE_TYPE("RESULTPATH");
@@ -2498,6 +2534,9 @@ _outNode(StringInfo str, void *obj)
 			case T_Append:
 				_outAppend(str, obj);
 				break;
+			case T_MergeAppend:
+				_outMergeAppend(str, obj);
+				break;
 			case T_RecursiveUnion:
 				_outRecursiveUnion(str, obj);
 				break;
@@ -2745,6 +2784,9 @@ _outNode(StringInfo str, void *obj)
 			case T_AppendPath:
 				_outAppendPath(str, obj);
 				break;
+			case T_MergeAppendPath:
+				_outMergeAppendPath(str, obj);
+				break;
 			case T_ResultPath:
 				_outResultPath(str, obj);
 				break;