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Fix bug with whole-row references to append subplans.
authorTom Lane <tgl@sss.pgh.pa.us>
Fri, 11 Jul 2014 23:12:56 +0000 (19:12 -0400)
committerTom Lane <tgl@sss.pgh.pa.us>
Fri, 11 Jul 2014 23:12:56 +0000 (19:12 -0400)
ExecEvalWholeRowVar incorrectly supposed that it could "bless" the source
TupleTableSlot just once per query.  But if the input is coming from an
Append (or, perhaps, other cases?) more than one slot might be returned
over the query run.  This led to "record type has not been registered"
errors when a composite datum was extracted from a non-blessed slot.

This bug has been there a long time; I guess it escaped notice because when
dealing with subqueries the planner tends to expand whole-row Vars into
RowExprs, which don't have the same problem.  It is possible to trigger
the problem in all active branches, though, as illustrated by the added
regression test.

src/backend/executor/execQual.c patch | blob | blame | history
src/test/regress/expected/subselect.out patch | blob | blame | history
src/test/regress/sql/subselect.sql patch | blob | blame | history

diff --git a/src/backend/executor/execQual.c b/src/backend/executor/execQual.c
index 8410032cf50c61e835061ba92a8c72b759b6bc4d..61c8d61530eb3fe4c18feab4a93adbe168f9bb98 100644 (file)
--- a/src/backend/executor/execQual.c
+++ b/src/backend/executor/execQual.c
@@ -712,7 +712,6 @@ ExecEvalWholeRowVar(WholeRowVarExprState *wrvstate, ExprContext *econtext,
 {
    Var        *variable = (Var *) wrvstate->xprstate.expr;
    TupleTableSlot *slot;
-   TupleDesc   slot_tupdesc;
    bool        needslow = false;
 
    if (isDone)
@@ -790,25 +789,14 @@ ExecEvalWholeRowVar(WholeRowVarExprState *wrvstate, ExprContext *econtext,
    if (wrvstate->wrv_junkFilter != NULL)
        slot = ExecFilterJunk(wrvstate->wrv_junkFilter, slot);
 
-   slot_tupdesc = slot->tts_tupleDescriptor;
-
    /*
-    * If it's a RECORD Var, we'll use the slot's type ID info.  It's likely
-    * that the slot's type is also RECORD; if so, make sure it's been
-    * "blessed", so that the Datum can be interpreted later.
-    *
     * If the Var identifies a named composite type, we must check that the
     * actual tuple type is compatible with it.
     */
-   if (variable->vartype == RECORDOID)
-   {
-       if (slot_tupdesc->tdtypeid == RECORDOID &&
-           slot_tupdesc->tdtypmod < 0)
-           assign_record_type_typmod(slot_tupdesc);
-   }
-   else
+   if (variable->vartype != RECORDOID)
    {
        TupleDesc   var_tupdesc;
+       TupleDesc   slot_tupdesc;
        int         i;
 
        /*
@@ -825,6 +813,8 @@ ExecEvalWholeRowVar(WholeRowVarExprState *wrvstate, ExprContext *econtext,
         */
        var_tupdesc = lookup_rowtype_tupdesc(variable->vartype, -1);
 
+       slot_tupdesc = slot->tts_tupleDescriptor;
+
        if (var_tupdesc->natts != slot_tupdesc->natts)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
@@ -882,6 +872,7 @@ ExecEvalWholeRowFast(WholeRowVarExprState *wrvstate, ExprContext *econtext,
 {
    Var        *variable = (Var *) wrvstate->xprstate.expr;
    TupleTableSlot *slot = econtext->ecxt_scantuple;
+   TupleDesc   slot_tupdesc;
    HeapTupleHeader dtuple;
 
    if (isDone)
@@ -892,6 +883,20 @@ ExecEvalWholeRowFast(WholeRowVarExprState *wrvstate, ExprContext *econtext,
    if (wrvstate->wrv_junkFilter != NULL)
        slot = ExecFilterJunk(wrvstate->wrv_junkFilter, slot);
 
+   /*
+    * If it's a RECORD Var, we'll use the slot's type ID info.  It's likely
+    * that the slot's type is also RECORD; if so, make sure it's been
+    * "blessed", so that the Datum can be interpreted later.  (Note: we must
+    * do this here, not in ExecEvalWholeRowVar, because some plan trees may
+    * return different slots at different times.  We have to be ready to
+    * bless additional slots during the run.)
+    */
+   slot_tupdesc = slot->tts_tupleDescriptor;
+   if (variable->vartype == RECORDOID &&
+       slot_tupdesc->tdtypeid == RECORDOID &&
+       slot_tupdesc->tdtypmod < 0)
+       assign_record_type_typmod(slot_tupdesc);
+
    /*
     * Copy the slot tuple and make sure any toasted fields get detoasted.
     */
diff --git a/src/test/regress/expected/subselect.out b/src/test/regress/expected/subselect.out
index c9d80bc045a1b3550f1262216dadbfef28a98afa..5d9aa4e2eb90a6e0a55a360d42ad29b142a9b1ac 100644 (file)
--- a/src/test/regress/expected/subselect.out
+++ b/src/test/regress/expected/subselect.out
@@ -662,3 +662,21 @@ select * from int4_tbl o where (f1, f1) in
 (1 row)
 
 reset enable_hashjoin;
+--
+-- check for over-optimization of whole-row Var referencing an Append plan
+--
+select (select q from
+         (select 1,2,3 where f1 > 0
+          union all
+          select 4,5,6.0 where f1 <= 0
+         ) q )
+from int4_tbl;
+ ?column?  
+-----------
+ (4,5,6.0)
+ (1,2,3)
+ (4,5,6.0)
+ (1,2,3)
+ (4,5,6.0)
+(5 rows)
+
diff --git a/src/test/regress/sql/subselect.sql b/src/test/regress/sql/subselect.sql
index a748889b23d4c2d2b038ea7750d96b11b15cf77b..2862bf791bcd122318fba49341e852958ae9fe81 100644 (file)
--- a/src/test/regress/sql/subselect.sql
+++ b/src/test/regress/sql/subselect.sql
@@ -404,3 +404,13 @@ set enable_hashjoin to 0;
 select * from int4_tbl o where (f1, f1) in
   (select f1, generate_series(1,2) / 10 g from int4_tbl i group by f1);
 reset enable_hashjoin;
+
+--
+-- check for over-optimization of whole-row Var referencing an Append plan
+--
+select (select q from
+         (select 1,2,3 where f1 > 0
+          union all
+          select 4,5,6.0 where f1 <= 0
+         ) q )
+from int4_tbl;
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