Fix handling of bare boolean expressions in mcv_get_match_bitmap.

Since v14, the extended stats machinery will try to estimate for
otherwise-unsupported boolean expressions if they match an expression
available from an extended stats object.  mcv.c did not get the memo
about this, and would spit up with "unknown clause type".  Fortunately
the case is easy to handle, since we can expect the expression yields
boolean.

While here, replace some not-terribly-on-point assertions with
simpler runtime tests for lookup failure.  That seems appropriate
so that we get an elog not a crash if we somehow get to the new
it-should-be-a-bool-expression code with a subexpression that
doesn't match any stats column.

Per report from Danny Shemesh.  Thanks to Justin Pryzby for
preliminary investigation.

Discussion: https://postgr.es/m/CAFZC=QqD6=27wQPOW1pbRa98KPyuyn+7cL_Ay_Ck-roZV84vHg@mail.gmail.com

diff --git a/src/backend/statistics/mcv.c b/src/backend/statistics/mcv.c
index 35bb21c43eae4da04ca67644fdfda045f61e26b9..0be53a89f9cef32bb2c0e7b6cf9fece109d213b3 100644 (file)
--- a/src/backend/statistics/mcv.c
+++ b/src/backend/statistics/mcv.c
@@ -1532,13 +1532,13 @@ pg_mcv_list_send(PG_FUNCTION_ARGS)
 /*
  * match the attribute/expression to a dimension of the statistic
  *
- * Match the attribute/expression to statistics dimension. Optionally
- * determine the collation.
+ * Returns the zero-based index of the matching statistics dimension.
+ * Optionally determines the collation.
  */
 static int
 mcv_match_expression(Node *expr, Bitmapset *keys, List *exprs, Oid *collid)
 {
-   int         idx = -1;
+   int         idx;
 
    if (IsA(expr, Var))
    {
@@ -1550,20 +1550,19 @@ mcv_match_expression(Node *expr, Bitmapset *keys, List *exprs, Oid *collid)
 
        idx = bms_member_index(keys, var->varattno);
 
-       /* make sure the index is valid */
-       Assert((idx >= 0) && (idx <= bms_num_members(keys)));
+       if (idx < 0)
+           elog(ERROR, "variable not found in statistics object");
    }
    else
    {
+       /* expression - lookup in stats expressions */
        ListCell   *lc;
 
-       /* expressions are stored after the simple columns */
-       idx = bms_num_members(keys);
-
        if (collid)
            *collid = exprCollation(expr);
 
-       /* expression - lookup in stats expressions */
+       /* expressions are stored after the simple columns */
+       idx = bms_num_members(keys);
        foreach(lc, exprs)
        {
            Node       *stat_expr = (Node *) lfirst(lc);
@@ -1574,13 +1573,10 @@ mcv_match_expression(Node *expr, Bitmapset *keys, List *exprs, Oid *collid)
            idx++;
        }
 
-       /* make sure the index is valid */
-       Assert((idx >= bms_num_members(keys)) &&
-              (idx <= bms_num_members(keys) + list_length(exprs)));
+       if (lc == NULL)
+           elog(ERROR, "expression not found in statistics object");
    }
 
-   Assert((idx >= 0) && (idx < bms_num_members(keys) + list_length(exprs)));
-
    return idx;
 }
 
@@ -1659,8 +1655,6 @@ mcv_get_match_bitmap(PlannerInfo *root, List *clauses,
            /* match the attribute/expression to a dimension of the statistic */
            idx = mcv_match_expression(clause_expr, keys, exprs, &collid);
 
-           Assert((idx >= 0) && (idx < bms_num_members(keys) + list_length(exprs)));
-
            /*
             * Walk through the MCV items and evaluate the current clause. We
             * can skip items that were already ruled out, and terminate if
@@ -1944,7 +1938,30 @@ mcv_get_match_bitmap(PlannerInfo *root, List *clauses,
            }
        }
        else
-           elog(ERROR, "unknown clause type: %d", clause->type);
+       {
+           /* Otherwise, it must be a bare boolean-returning expression */
+           int         idx;
+
+           /* match the expression to a dimension of the statistic */
+           idx = mcv_match_expression(clause, keys, exprs, NULL);
+
+           /*
+            * Walk through the MCV items and evaluate the current clause. We
+            * can skip items that were already ruled out, and terminate if
+            * there are no remaining MCV items that might possibly match.
+            */
+           for (i = 0; i < mcvlist->nitems; i++)
+           {
+               bool        match;
+               MCVItem    *item = &mcvlist->items[i];
+
+               /* "match" just means it's bool TRUE */
+               match = !item->isnull[idx] && DatumGetBool(item->values[idx]);
+
+               /* now, update the match bitmap, depending on OR/AND type */
+               matches[i] = RESULT_MERGE(matches[i], is_or, match);
+           }
+       }
    }
 
    return matches;

diff --git a/src/test/regress/expected/stats_ext.out b/src/test/regress/expected/stats_ext.out
index fbd872524a66016c3c4fdbc76409fe71a203eaa7..1b1a5e1112a3c676e431016a42b21bce5e71236c 100644 (file)
--- a/src/test/regress/expected/stats_ext.out
+++ b/src/test/regress/expected/stats_ext.out
@@ -271,14 +271,23 @@ SELECT stxkind FROM pg_statistic_ext WHERE stxname = 'ab1_exprstat_3';
 CREATE STATISTICS ab1_exprstat_4 ON date_trunc('day', d) FROM ab1;
 -- date_trunc on timestamp is immutable
 CREATE STATISTICS ab1_exprstat_5 ON date_trunc('day', c) FROM ab1;
+-- check use of a boolean-returning expression
+CREATE STATISTICS ab1_exprstat_6 ON
+  (case a when 1 then true else false end), b FROM ab1;
 -- insert some data and run analyze, to test that these cases build properly
 INSERT INTO ab1
-SELECT
-    generate_series(1,10),
-    generate_series(1,10),
-    generate_series('2020-10-01'::timestamp, '2020-10-10'::timestamp, interval '1 day'),
-    generate_series('2020-10-01'::timestamptz, '2020-10-10'::timestamptz, interval '1 day');
+SELECT x / 10, x / 3,
+    '2020-10-01'::timestamp + x * interval '1 day',
+    '2020-10-01'::timestamptz + x * interval '1 day'
+FROM generate_series(1, 100) x;
 ANALYZE ab1;
+-- apply some stats
+SELECT * FROM check_estimated_rows('SELECT * FROM ab1 WHERE (case a when 1 then true else false end) AND b=2');
+ estimated | actual 
+-----------+--------
+         1 |      0
+(1 row)
+
 DROP TABLE ab1;
 -- Verify supported object types for extended statistics
 CREATE schema tststats;

diff --git a/src/test/regress/sql/stats_ext.sql b/src/test/regress/sql/stats_ext.sql
index 4394ede8c8b383ec3b19e465e1e80b76acd8d58f..b9237982d4855d02e9dfb6f34dc27dff0d815300 100644 (file)
--- a/src/test/regress/sql/stats_ext.sql
+++ b/src/test/regress/sql/stats_ext.sql
@@ -165,14 +165,21 @@ CREATE STATISTICS ab1_exprstat_4 ON date_trunc('day', d) FROM ab1;
 -- date_trunc on timestamp is immutable
 CREATE STATISTICS ab1_exprstat_5 ON date_trunc('day', c) FROM ab1;
 
+-- check use of a boolean-returning expression
+CREATE STATISTICS ab1_exprstat_6 ON
+  (case a when 1 then true else false end), b FROM ab1;
+
 -- insert some data and run analyze, to test that these cases build properly
 INSERT INTO ab1
-SELECT
-    generate_series(1,10),
-    generate_series(1,10),
-    generate_series('2020-10-01'::timestamp, '2020-10-10'::timestamp, interval '1 day'),
-    generate_series('2020-10-01'::timestamptz, '2020-10-10'::timestamptz, interval '1 day');
+SELECT x / 10, x / 3,
+    '2020-10-01'::timestamp + x * interval '1 day',
+    '2020-10-01'::timestamptz + x * interval '1 day'
+FROM generate_series(1, 100) x;
 ANALYZE ab1;
+
+-- apply some stats
+SELECT * FROM check_estimated_rows('SELECT * FROM ab1 WHERE (case a when 1 then true else false end) AND b=2');
+
 DROP TABLE ab1;
 
 -- Verify supported object types for extended statistics