Avoid an Assert failure in deconstruct_array() by making get_attstatsslot()

use the actual element type of the array it's disassembling, rather than
trusting the type OID passed in by its caller.  This is needed because
sometimes the planner passes in a type OID that's only binary-compatible
with the target column's type, rather than being an exact match.  Per an
example from Bernd Helmle.

Possibly we should refactor get_attstatsslot/free_attstatsslot to not expect
the caller to supply type ID data at all, but for now I'll just do the
minimum-change fix.

Back-patch to 7.4.  Bernd's test case only crashes back to 8.0, but since
these subroutines are the same in 7.4, I suspect there may be variant
cases that would crash 7.4 as well.

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 15b676dd590aeef6a416e2e5f782f0b2acc9cd93..8035969187cd4a21b49449e903bad5387bcb8503 100644 (file)
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *   $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.129.2.1 2007/10/13 15:55:58 tgl Exp $
+ *   $PostgreSQL: pgsql/src/backend/utils/cache/lsyscache.c,v 1.129.2.2 2010/07/09 22:58:12 tgl Exp $
  *
  * NOTES
  *   Eventually, the index information should go through here, too.
@@ -1881,6 +1881,10 @@ get_attavgwidth(Oid relid, AttrNumber attnum)
  * If the attribute type is pass-by-reference, the values referenced by
  * the values array are themselves palloc'd.  The palloc'd stuff can be
  * freed by calling free_attstatsslot.
+ *
+ * Note: at present, atttype/atttypmod aren't actually used here at all.
+ * But the caller must have the correct (or at least binary-compatible)
+ * type ID to pass to free_attstatsslot later.
  */
 bool
 get_attstatsslot(HeapTuple statstuple,
@@ -1895,6 +1899,7 @@ get_attstatsslot(HeapTuple statstuple,
    Datum       val;
    bool        isnull;
    ArrayType  *statarray;
+   Oid         arrayelemtype;
    int         narrayelem;
    HeapTuple   typeTuple;
    Form_pg_type typeForm;
@@ -1917,17 +1922,24 @@ get_attstatsslot(HeapTuple statstuple,
            elog(ERROR, "stavalues is null");
        statarray = DatumGetArrayTypeP(val);
 
-       /* Need to get info about the array element type */
+       /*
+        * Need to get info about the array element type.  We look at the
+        * actual element type embedded in the array, which might be only
+        * binary-compatible with the passed-in atttype.  The info we
+        * extract here should be the same either way, but deconstruct_array
+        * is picky about having an exact type OID match.
+        */
+       arrayelemtype = ARR_ELEMTYPE(statarray);
        typeTuple = SearchSysCache(TYPEOID,
-                                  ObjectIdGetDatum(atttype),
+                                  ObjectIdGetDatum(arrayelemtype),
                                   0, 0, 0);
        if (!HeapTupleIsValid(typeTuple))
-           elog(ERROR, "cache lookup failed for type %u", atttype);
+           elog(ERROR, "cache lookup failed for type %u", arrayelemtype);
        typeForm = (Form_pg_type) GETSTRUCT(typeTuple);
 
        /* Deconstruct array into Datum elements */
        deconstruct_array(statarray,
-                         atttype,
+                         arrayelemtype,
                          typeForm->typlen,
                          typeForm->typbyval,
                          typeForm->typalign,