Fix planning of btree index scans using ScalarArrayOpExpr quals.

In commit 9e8da0f75731aaa7605cf4656c21ea09e84d2eb1, I improved btree
to handle ScalarArrayOpExpr quals natively, so that constructs like
"indexedcol IN (list)" could be supported by index-only scans.  Using
such a qual results in multiple scans of the index, under-the-hood.
I went to some lengths to ensure that this still produces rows in index
order ... but I failed to recognize that if a higher-order index column
is lacking an equality constraint, rescans can produce out-of-order
data from that column.  Tweak the planner to not expect sorted output
in that case.  Per trouble report from Robert McGehee.

diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 53bf15aea23ec151de6803f7ac3fca7d7f818378..444ec2a40e4ac2b0ed8435017149c7664869e34c 100644 (file)
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -787,6 +787,7 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
        List       *index_pathkeys;
        List       *useful_pathkeys;
        bool            found_clause;
+       bool            found_lower_saop_clause;
        bool            pathkeys_possibly_useful;
        bool            index_is_ordered;
        bool            index_only_scan;
@@ -824,6 +825,13 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
         * if saop_control is SAOP_REQUIRE, it has to be a ScalarArrayOpExpr
         * clause.
         *
+        * found_lower_saop_clause is set true if there's a ScalarArrayOpExpr
+        * index clause for a non-first index column.  This prevents us from
+        * assuming that the scan result is ordered.  (Actually, the result is
+        * still ordered if there are equality constraints for all earlier
+        * columns, but it seems too expensive and non-modular for this code to be
+        * aware of that refinement.)
+        *
         * We also build a Relids set showing which outer rels are required by the
         * selected clauses.  Any lateral_relids are included in that, but not
         * otherwise accounted for.
@@ -831,6 +839,7 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
        index_clauses = NIL;
        clause_columns = NIL;
        found_clause = false;
+       found_lower_saop_clause = false;
        outer_relids = bms_copy(rel->lateral_relids);
        for (indexcol = 0; indexcol < index->ncolumns; indexcol++)
        {
@@ -846,6 +855,8 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
                                if (saop_control == SAOP_PER_AM && !index->amsearcharray)
                                        continue;
                                found_clause = true;
+                               if (indexcol > 0)
+                                       found_lower_saop_clause = true;
                        }
                        else
                        {
@@ -882,9 +893,11 @@ build_index_paths(PlannerInfo *root, RelOptInfo *rel,
        /*
         * 2. Compute pathkeys describing index's ordering, if any, then see how
         * many of them are actually useful for this query.  This is not relevant
-        * if we are only trying to build bitmap indexscans.
+        * if we are only trying to build bitmap indexscans, nor if we have to
+        * assume the scan is unordered.
         */
        pathkeys_possibly_useful = (scantype != ST_BITMAPSCAN &&
+                                                               !found_lower_saop_clause &&
                                                                has_useful_pathkeys(root, rel));
        index_is_ordered = (index->sortopfamily != NULL);
        if (index_is_ordered && pathkeys_possibly_useful)

diff --git a/src/test/regress/expected/create_index.out b/src/test/regress/expected/create_index.out
index 999e38a67986ce4af46bfa7d94d1fd45159b0eda..2ae991eebe282dc1201c85194b804337a25c66e8 100644 (file)
--- a/src/test/regress/expected/create_index.out
+++ b/src/test/regress/expected/create_index.out
@@ -2676,3 +2676,48 @@ SELECT count(*) FROM dupindexcols
     97
 (1 row)
 
+--
+-- Check ordering of =ANY indexqual results (bug in 9.2.0)
+--
+vacuum analyze tenk1;          -- ensure we get consistent plans here
+explain (costs off)
+SELECT unique1 FROM tenk1
+WHERE unique1 IN (1,42,7)
+ORDER BY unique1;
+                      QUERY PLAN                       
+-------------------------------------------------------
+ Index Only Scan using tenk1_unique1 on tenk1
+   Index Cond: (unique1 = ANY ('{1,42,7}'::integer[]))
+(2 rows)
+
+SELECT unique1 FROM tenk1
+WHERE unique1 IN (1,42,7)
+ORDER BY unique1;
+ unique1 
+---------
+       1
+       7
+      42
+(3 rows)
+
+explain (costs off)
+SELECT thousand, tenthous FROM tenk1
+WHERE thousand < 2 AND tenthous IN (1001,3000)
+ORDER BY thousand;
+                                      QUERY PLAN                                      
+--------------------------------------------------------------------------------------
+ Sort
+   Sort Key: thousand
+   ->  Index Only Scan using tenk1_thous_tenthous on tenk1
+         Index Cond: ((thousand < 2) AND (tenthous = ANY ('{1001,3000}'::integer[])))
+(4 rows)
+
+SELECT thousand, tenthous FROM tenk1
+WHERE thousand < 2 AND tenthous IN (1001,3000)
+ORDER BY thousand;
+ thousand | tenthous 
+----------+----------
+        0 |     3000
+        1 |     1001
+(2 rows)
+

diff --git a/src/test/regress/sql/create_index.sql b/src/test/regress/sql/create_index.sql
index f8edb7ee76607ac3d0c4ce0260d234436405a0d5..914e7a57a472be210a089a04c3b9e7d8660975b1 100644 (file)
--- a/src/test/regress/sql/create_index.sql
+++ b/src/test/regress/sql/create_index.sql
@@ -888,3 +888,27 @@ EXPLAIN (COSTS OFF)
     WHERE f1 > 'WA' and id < 1000 and f1 ~<~ 'YX';
 SELECT count(*) FROM dupindexcols
   WHERE f1 > 'WA' and id < 1000 and f1 ~<~ 'YX';
+
+--
+-- Check ordering of =ANY indexqual results (bug in 9.2.0)
+--
+
+vacuum analyze tenk1;          -- ensure we get consistent plans here
+
+explain (costs off)
+SELECT unique1 FROM tenk1
+WHERE unique1 IN (1,42,7)
+ORDER BY unique1;
+
+SELECT unique1 FROM tenk1
+WHERE unique1 IN (1,42,7)
+ORDER BY unique1;
+
+explain (costs off)
+SELECT thousand, tenthous FROM tenk1
+WHERE thousand < 2 AND tenthous IN (1001,3000)
+ORDER BY thousand;
+
+SELECT thousand, tenthous FROM tenk1
+WHERE thousand < 2 AND tenthous IN (1001,3000)
+ORDER BY thousand;