From 29c4ad98293e3c5cb3fcdd413a3f4904efff8762 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 1 Jan 2010 21:53:49 +0000
Subject: Support "x IS NOT NULL" clauses as indexscan conditions.  This turns
 out to be just a minor extension of the previous patch that made "x IS NULL"
 indexable, because we can treat the IS NOT NULL condition as if it were "x <
 NULL" or "x > NULL" (depending on the index's NULLS FIRST/LAST option), just
 like IS NULL is treated like "x = NULL".  Aside from any possible usefulness
 in its own right, this is an important improvement for index-optimized
 MAX/MIN aggregates: it is now reliably possible to get a column's min or max
 value cheaply, even when there are a lot of nulls cluttering the interesting
 end of the index.

---
 src/backend/executor/nodeIndexscan.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

(limited to 'src/backend/executor/nodeIndexscan.c')

diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
index b136825dc8..df877ae191 100644
--- a/src/backend/executor/nodeIndexscan.c
+++ b/src/backend/executor/nodeIndexscan.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.136 2009/10/26 02:26:31 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.137 2010/01/01 21:53:49 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -640,7 +640,8 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
  * (Note that we treat all array-expressions as requiring runtime evaluation,
  * even if they happen to be constants.)
  *
- * 5. NullTest ("indexkey IS NULL").  We just fill in the ScanKey properly.
+ * 5. NullTest ("indexkey IS NULL/IS NOT NULL").  We just fill in the
+ * ScanKey properly.
  *
  * Input params are:
  *
@@ -987,13 +988,14 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
 		}
 		else if (IsA(clause, NullTest))
 		{
-			/* indexkey IS NULL */
-			Assert(((NullTest *) clause)->nulltesttype == IS_NULL);
+			/* indexkey IS NULL or indexkey IS NOT NULL */
+			NullTest   *ntest = (NullTest *) clause;
+			int			flags;
 
 			/*
 			 * argument should be the index key Var, possibly relabeled
 			 */
-			leftop = ((NullTest *) clause)->arg;
+			leftop = ntest->arg;
 
 			if (leftop && IsA(leftop, RelabelType))
 				leftop = ((RelabelType *) leftop)->arg;
@@ -1009,8 +1011,23 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index, Index scanrelid,
 			/*
 			 * initialize the scan key's fields appropriately
 			 */
+			switch (ntest->nulltesttype)
+			{
+				case IS_NULL:
+					flags = SK_ISNULL | SK_SEARCHNULL;
+					break;
+				case IS_NOT_NULL:
+					flags = SK_ISNULL | SK_SEARCHNOTNULL;
+					break;
+				default:
+					elog(ERROR, "unrecognized nulltesttype: %d",
+						 (int) ntest->nulltesttype);
+					flags = 0;	/* keep compiler quiet */
+					break;
+			}
+
 			ScanKeyEntryInitialize(this_scan_key,
-								   SK_ISNULL | SK_SEARCHNULL,
+								   flags,
 								   varattno,	/* attribute number to scan */
 								   InvalidStrategy,		/* no strategy */
 								   InvalidOid,	/* no strategy subtype */
-- 
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