Add TID Range Scans to support efficient scanning ranges of TIDs

This adds a new executor node named TID Range Scan.  The query planner
will generate paths for TID Range scans when quals are discovered on base
relations which search for ranges on the table's ctid column.  These
ranges may be open at either end. For example, WHERE ctid >= '(10,0)';
will return all tuples on page 10 and over.

To support this, two new optional callback functions have been added to
table AM.  scan_set_tidrange is used to set the scan range to just the
given range of TIDs.  scan_getnextslot_tidrange fetches the next tuple
in the given range.

For AMs were scanning ranges of TIDs would not make sense, these functions
can be set to NULL in the TableAmRoutine.  The query planner won't
generate TID Range Scan Paths in that case.

Author: Edmund Horner, David Rowley
Reviewed-by: David Rowley, Tomas Vondra, Tom Lane, Andres Freund, Zhihong Yu
Discussion: https://postgr.es/m/CAMyN-kB-nFTkF=VA_JPwFNo08S0d-Yk0F741S2B7LDmYAi8eyA@mail.gmail.com

2 files changed, 38 insertions, 0 deletions

diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 65bbc18ecba..aaba1ec2c4a 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -586,6 +586,27 @@ _copyTidScan(const TidScan *from)
 }
 
 /*
+ * _copyTidRangeScan
+ */
+static TidRangeScan *
+_copyTidRangeScan(const TidRangeScan *from)
+{
+	TidRangeScan *newnode = makeNode(TidRangeScan);
+
+	/*
+	 * copy node superclass fields
+	 */
+	CopyScanFields((const Scan *) from, (Scan *) newnode);
+
+	/*
+	 * copy remainder of node
+	 */
+	COPY_NODE_FIELD(tidrangequals);
+
+	return newnode;
+}
+
+/*
  * _copySubqueryScan
  */
 static SubqueryScan *
@@ -4938,6 +4959,9 @@ copyObjectImpl(const void *from)
 		case T_TidScan:
 			retval = _copyTidScan(from);
 			break;
+		case T_TidRangeScan:
+			retval = _copyTidRangeScan(from);
+			break;
 		case T_SubqueryScan:
 			retval = _copySubqueryScan(from);
 			break;
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index f5dcedf6e89..8fc432bfe17 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -609,6 +609,16 @@ _outTidScan(StringInfo str, const TidScan *node)
 }
 
 static void
+_outTidRangeScan(StringInfo str, const TidRangeScan *node)
+{
+	WRITE_NODE_TYPE("TIDRANGESCAN");
+
+	_outScanInfo(str, (const Scan *) node);
+
+	WRITE_NODE_FIELD(tidrangequals);
+}
+
+static void
 _outSubqueryScan(StringInfo str, const SubqueryScan *node)
 {
 	WRITE_NODE_TYPE("SUBQUERYSCAN");
@@ -2314,6 +2324,7 @@ _outRelOptInfo(StringInfo str, const RelOptInfo *node)
 	WRITE_NODE_FIELD(subroot);
 	WRITE_NODE_FIELD(subplan_params);
 	WRITE_INT_FIELD(rel_parallel_workers);
+	WRITE_UINT_FIELD(amflags);
 	WRITE_OID_FIELD(serverid);
 	WRITE_OID_FIELD(userid);
 	WRITE_BOOL_FIELD(useridiscurrent);
@@ -3810,6 +3821,9 @@ outNode(StringInfo str, const void *obj)
 			case T_TidScan:
 				_outTidScan(str, obj);
 				break;
+			case T_TidRangeScan:
+				_outTidRangeScan(str, obj);
+				break;
 			case T_SubqueryScan:
 				_outSubqueryScan(str, obj);
 				break;