Make 'col IS NULL' clauses be indexable conditions.

Teodor Sigaev, with some kibitzing from Tom Lane.

1 files changed, 36 insertions, 2 deletions

diff --git a/src/backend/executor/nodeIndexscan.c b/src/backend/executor/nodeIndexscan.c
index 5f0a66f92bb..d9136de0035 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 1.120 2007/01/05 22:19:28 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/executor/nodeIndexscan.c,v 1.121 2007/04/06 22:33:42 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -599,7 +599,7 @@ ExecInitIndexScan(IndexScan *node, EState *estate, int eflags)
  * The index quals are passed to the index AM in the form of a ScanKey array.
  * This routine sets up the ScanKeys, fills in all constant fields of the
  * ScanKeys, and prepares information about the keys that have non-constant
- * comparison values.  We divide index qual expressions into four types:
+ * comparison values.  We divide index qual expressions into five types:
  *
  * 1. Simple operator with constant comparison value ("indexkey op constant").
  * For these, we just fill in a ScanKey containing the constant value.
@@ -620,6 +620,8 @@ 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.
+ *
  * Input params are:
  *
  * planstate: executor state node we are working for
@@ -956,6 +958,38 @@ ExecIndexBuildScanKeys(PlanState *planstate, Relation index,
 								   opfuncid,	/* reg proc to use */
 								   (Datum) 0);	/* constant */
 		}
+		else if (IsA(clause, NullTest))
+		{
+			/* indexkey IS NULL */
+			Assert(((NullTest *) clause)->nulltesttype == IS_NULL);
+
+			/*
+			 * argument should be the index key Var, possibly relabeled
+			 */
+			leftop = ((NullTest *) clause)->arg;
+
+			if (leftop && IsA(leftop, RelabelType))
+				leftop = ((RelabelType *) leftop)->arg;
+
+			 Assert(leftop != NULL);
+
+			if (!(IsA(leftop, Var) &&
+				  var_is_rel((Var *) leftop)))
+				elog(ERROR, "NullTest indexqual has wrong key");
+
+			varattno = ((Var *) leftop)->varattno;
+
+			/*
+			 * initialize the scan key's fields appropriately
+			 */
+			ScanKeyEntryInitialize(this_scan_key,
+								   SK_ISNULL | SK_SEARCHNULL,
+								   varattno,    /* attribute number to scan */
+								   strategy,    /* op's strategy */
+								   subtype,		/* strategy subtype */
+								   InvalidOid,	/* no reg proc for this */
+								   (Datum) 0);	/* constant */
+		}
 		else
 			elog(ERROR, "unsupported indexqual type: %d",
 				 (int) nodeTag(clause));