Remove dead NoMovementScanDirection code

Here remove some dead code from heapgettup() and heapgettup_pagemode()
which was trying to support NoMovementScanDirection scans.  This code can
never be reached as standard_ExecutorRun() never calls ExecutePlan with
NoMovementScanDirection.

Additionally, plans which were scanning an unordered index would use
NoMovementScanDirection rather than ForwardScanDirection.  There was no
real need for this, so here we adjust this so we use ForwardScanDirection
for unordered index scans.  A comment in pathnodes.h claimed that
NoMovementScanDirection was used for PathKey reasons, but if that was
true, it no longer is, per code in build_index_paths().

This does change the non-text format of the EXPLAIN output so that
unordered index scans now have a "Forward" scan direction rather than
"NoMovement".  The text format of EXPLAIN has not changed.

Author: Melanie Plageman
Reviewed-by: Tom Lane, David Rowley
Discussion: https://postgr.es/m/CAAKRu_bvkhka0CZQun28KTqhuUh5ZqY=_T8QEqZqOL02rpi2bw@mail.gmail.com

1 files changed, 7 insertions, 9 deletions

diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
index f1ced9ff0fa..4540c7781d2 100644
--- a/src/backend/executor/nodeIndexscan.c
+++ b/src/backend/executor/nodeIndexscan.c
@@ -90,15 +90,13 @@ IndexNext(IndexScanState *node)
 	 * extract necessary information from index scan node
 	 */
 	estate = node->ss.ps.state;
-	direction = estate->es_direction;
-	/* flip direction if this is an overall backward scan */
-	if (ScanDirectionIsBackward(((IndexScan *) node->ss.ps.plan)->indexorderdir))
-	{
-		if (ScanDirectionIsForward(direction))
-			direction = BackwardScanDirection;
-		else if (ScanDirectionIsBackward(direction))
-			direction = ForwardScanDirection;
-	}
+
+	/*
+	 * Determine which direction to scan the index in based on the plan's scan
+	 * direction and the current direction of execution.
+	 */
+	direction = ScanDirectionCombine(estate->es_direction,
+									 ((IndexScan *) node->ss.ps.plan)->indexorderdir);
 	scandesc = node->iss_ScanDesc;
 	econtext = node->ss.ps.ps_ExprContext;
 	slot = node->ss.ss_ScanTupleSlot;