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.

diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c
index 6b399d34a66b229cd75fd8617e4476e746be5df3..3686d31b843034a7539c4aeae1d29f075a8c2bae 100644 (file)
--- a/src/backend/access/nbtree/nbtutils.c
+++ b/src/backend/access/nbtree/nbtutils.c
@@ -323,8 +323,14 @@ _bt_preprocess_keys(IndexScanDesc scan)
 
                        /*
                         * If = has been specified, all other keys can be eliminated as
-                        * redundant.  In case of key > 2 && key == 1 we can set qual_ok
-                        * to false and abandon further processing.
+                        * redundant.  If we have a case like key = 1 AND key > 2, we can
+                        * set qual_ok to false and abandon further processing.
+                        *
+                        * We also have to deal with the case of "key IS NULL", which is
+                        * unsatisfiable in combination with any other index condition.
+                        * By the time we get here, that's been classified as an equality
+                        * check, and we've rejected any combination of it with a regular
+                        * equality condition; but not with other types of conditions.
                         */
                        if (xform[BTEqualStrategyNumber - 1])
                        {
@@ -337,6 +343,13 @@ _bt_preprocess_keys(IndexScanDesc scan)
                                        if (!chk || j == (BTEqualStrategyNumber - 1))
                                                continue;
 
+                                       if (eq->sk_flags & SK_SEARCHNULL)
+                                       {
+                                               /* IS NULL is contradictory to anything else */
+                                               so->qual_ok = false;
+                                               return;
+                                       }
+
                                        if (_bt_compare_scankey_args(scan, chk, eq, chk,
                                                                                                 &test_result))
                                        {

diff --git a/src/test/regress/expected/create_index.out b/src/test/regress/expected/create_index.out
index 22753437040c091da871df2328ee3378e009f552..f2c0923730393b4d8d0556d6bf69798445a55c4e 100644 (file)
--- a/src/test/regress/expected/create_index.out
+++ b/src/test/regress/expected/create_index.out
@@ -942,6 +942,18 @@ 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;
@@ -968,6 +980,18 @@ 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;
@@ -994,6 +1018,18 @@ 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;
@@ -1020,6 +1056,18 @@ 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 a4261c0f5e2cd608dce7a1a180b937dfc9492d9a..62f439c3f0f76c6488e7165377d79dca73189140 100644 (file)
--- a/src/test/regress/sql/create_index.sql
+++ b/src/test/regress/sql/create_index.sql
@@ -393,6 +393,8 @@ 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;
 
@@ -402,6 +404,8 @@ 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;
 
@@ -411,6 +415,8 @@ 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;
 
@@ -420,6 +426,8 @@ 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;