Fix bug with whole-row references to append subplans.

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.

diff --git a/src/backend/executor/execQual.c b/src/backend/executor/execQual.c
index 81b404b5265f212596d235dae2516b1dd0027ae9..f5f506c3b8356d101c9adb19799e499cfb62bcc9 100644 (file)
--- a/src/backend/executor/execQual.c
+++ b/src/backend/executor/execQual.c
@@ -704,7 +704,6 @@ ExecEvalWholeRowVar(WholeRowVarExprState *wrvstate, ExprContext *econtext,
 {
        Var                *variable = (Var *) wrvstate->xprstate.expr;
        TupleTableSlot *slot;
-       TupleDesc       slot_tupdesc;
        bool            needslow = false;
 
        if (isDone)
@@ -794,25 +793,14 @@ 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;
 
                /*
@@ -829,6 +817,8 @@ 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),
@@ -886,6 +876,7 @@ ExecEvalWholeRowFast(WholeRowVarExprState *wrvstate, ExprContext *econtext,
 {
        Var                *variable = (Var *) wrvstate->xprstate.expr;
        TupleTableSlot *slot;
+       TupleDesc       slot_tupdesc;
        HeapTupleHeader dtuple;
 
        if (isDone)
@@ -913,6 +904,20 @@ 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 d31c8dc90a4d9c2f7555aded245040aff26e8076..5aac212c2963a7fec8f4b63ba168fbd343699d35 100644 (file)
--- a/src/test/regress/expected/subselect.out
+++ b/src/test/regress/expected/subselect.out
@@ -765,3 +765,21 @@ 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 eb88f948be55fc99ea448ae38998dcfa8178829d..42f1a907b3981fb0f0168d8a85f256920556fb03 100644 (file)
--- a/src/test/regress/sql/subselect.sql
+++ b/src/test/regress/sql/subselect.sql
@@ -427,3 +427,13 @@ select * from int4_tbl o where (f1, f1) in
 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;