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

1 files changed, 18 insertions, 0 deletions

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 943931f65d0..e31ad6204e6 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1625,6 +1625,24 @@ typedef struct TidScanState
 } TidScanState;
 
 /* ----------------
+ *	 TidRangeScanState information
+ *
+ *		trss_tidexprs		list of TidOpExpr structs (see nodeTidrangescan.c)
+ *		trss_mintid			the lowest TID in the scan range
+ *		trss_maxtid			the highest TID in the scan range
+ *		trss_inScan			is a scan currently in progress?
+ * ----------------
+ */
+typedef struct TidRangeScanState
+{
+	ScanState	ss;				/* its first field is NodeTag */
+	List	   *trss_tidexprs;
+	ItemPointerData trss_mintid;
+	ItemPointerData trss_maxtid;
+	bool		trss_inScan;
+} TidRangeScanState;
+
+/* ----------------
  *	 SubqueryScanState information
  *
  *		SubqueryScanState is used for scanning a sub-query in the range table.