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 c6f31a0ad0b672eef99575340cd8d7a69afe0eec..229c2b051b2aa269afa1ead3228da107437031f1 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)
@@ -804,25 +803,14 @@ 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;
 
        /*
@@ -839,6 +827,8 @@ 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),
@@ -896,6 +886,7 @@ ExecEvalWholeRowFast(WholeRowVarExprState *wrvstate, ExprContext *econtext,
 {
    Var        *variable = (Var *) wrvstate->xprstate.expr;
    TupleTableSlot *slot;
+   TupleDesc   slot_tupdesc;
    HeapTupleHeader dtuple;
 
    if (isDone)
@@ -925,6 +916,20 @@ 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 5f2fac14f9bccdaf1cfcda508f5479662636a3ff..862185dddd810626a5d44627f575c277d537c3a6 100644 (file)
--- a/src/test/regress/expected/subselect.out
+++ b/src/test/regress/expected/subselect.out
@@ -772,3 +772,21 @@ select * from int4_tbl o where (f1, f1) in
   0
 (1 row)
 
+--
+-- 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;
+     q     
+-----------
+ (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 1975902726f99e02c2c4d579cd9869e529c13ff2..55ff70d47cd51e6937b3e3d87a2b7bd492d72d9b 100644 (file)
--- a/src/test/regress/sql/subselect.sql
+++ b/src/test/regress/sql/subselect.sql
@@ -431,3 +431,13 @@ select * from int4_tbl o where (f1, f1) in
   (select f1, generate_series(1,2) / 10 g from int4_tbl i group by f1);
 select * from int4_tbl o where (f1, f1) in
   (select f1, generate_series(1,2) / 10 g from int4_tbl i group by f1);
+
+--
+-- 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;