Restore correct btree preprocessing of "indexedcol IS NULL" conditions.

Such a condition is unsatisfiable in combination with any other type of
btree-indexable condition (since we assume btree operators are always
strict).  8.3 and 8.4 had an explicit test for this, which I removed in
commit 29c4ad98293e3c5cb3fcdd413a3f4904efff8762, mistakenly thinking that
the case would be subsumed by the more general handling of IS (NOT) NULL
added in that patch.  Put it back, and improve the comments about it, and
add a regression test case.

Per bug #6079 from Renat Nasyrov, and analysis by Dean Rasheed.

2 files changed, 56 insertions, 0 deletions

diff --git a/src/test/regress/expected/create_index.out b/src/test/regress/expected/create_index.out
index c78d9ee1e80..b23c712204e 100644
--- a/src/test/regress/expected/create_index.out
+++ b/src/test/regress/expected/create_index.out
@@ -1279,6 +1279,18 @@ SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NOT NUL
      1
 (1 row)
 
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL AND unique1 > 500;
+ count 
+-------
+   499
+(1 row)
+
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique1 > 500;
+ count 
+-------
+     0
+(1 row)
+
 DROP INDEX onek_nulltest;
 CREATE UNIQUE INDEX onek_nulltest ON onek_with_null (unique2 desc,unique1);
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL;
@@ -1305,6 +1317,18 @@ SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NOT NUL
      1
 (1 row)
 
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL AND unique1 > 500;
+ count 
+-------
+   499
+(1 row)
+
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique1 > 500;
+ count 
+-------
+     0
+(1 row)
+
 DROP INDEX onek_nulltest;
 CREATE UNIQUE INDEX onek_nulltest ON onek_with_null (unique2 desc nulls last,unique1);
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL;
@@ -1331,6 +1355,18 @@ SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NOT NUL
      1
 (1 row)
 
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL AND unique1 > 500;
+ count 
+-------
+   499
+(1 row)
+
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique1 > 500;
+ count 
+-------
+     0
+(1 row)
+
 DROP INDEX onek_nulltest;
 CREATE UNIQUE INDEX onek_nulltest ON onek_with_null (unique2  nulls first,unique1);
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL;
@@ -1357,6 +1393,18 @@ SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NOT NUL
      1
 (1 row)
 
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL AND unique1 > 500;
+ count 
+-------
+   499
+(1 row)
+
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique1 > 500;
+ count 
+-------
+     0
+(1 row)
+
 RESET enable_seqscan;
 RESET enable_indexscan;
 RESET enable_bitmapscan;
diff --git a/src/test/regress/sql/create_index.sql b/src/test/regress/sql/create_index.sql
index 31b49ca2273..bf27379f591 100644
--- a/src/test/regress/sql/create_index.sql
+++ b/src/test/regress/sql/create_index.sql
@@ -451,6 +451,8 @@ SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NOT NULL;
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL AND unique1 > 500;
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique1 > 500;
 
 DROP INDEX onek_nulltest;
 
@@ -460,6 +462,8 @@ SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NOT NULL;
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL AND unique1 > 500;
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique1 > 500;
 
 DROP INDEX onek_nulltest;
 
@@ -469,6 +473,8 @@ SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NOT NULL;
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL AND unique1 > 500;
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique1 > 500;
 
 DROP INDEX onek_nulltest;
 
@@ -478,6 +484,8 @@ SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL;
 SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique2 IS NOT NULL;
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NOT NULL AND unique1 > 500;
+SELECT count(*) FROM onek_with_null WHERE unique1 IS NULL AND unique1 > 500;
 
 RESET enable_seqscan;
 RESET enable_indexscan;