Fix handling of non-key columns get_index_column_opclass()

f2e40380 introduces support of non-key attributes in GiST indexes.  Then if
get_index_column_opclass() is asked by gistproperty() to get an opclass of
non-key column, it returns garbage past oidvector value.  This commit fixes
that by making get_index_column_opclass() return InvalidOid in this case.

Discussion: https://postgr.es/m/20190902231948.GA5343%40alvherre.pgsql
Author: Nikita Glukhov, Alexander Korotkov
Backpatch-through: 12

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index c13c08a97b4871c58451a675659d34e688fdc8ce..27602fa49c6b5c3677403e4363ecc4530bb664f1 100644 (file)
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -3157,7 +3157,8 @@ get_range_subtype(Oid rangeOid)
  *
  *             Given the index OID and column number,
  *             return opclass of the index column
- *                     or InvalidOid if the index was not found.
+ *                     or InvalidOid if the index was not found
+ *                             or column is non-key one.
  */
 Oid
 get_index_column_opclass(Oid index_oid, int attno)
@@ -3180,11 +3181,20 @@ get_index_column_opclass(Oid index_oid, int attno)
        /* caller is supposed to guarantee this */
        Assert(attno > 0 && attno <= rd_index->indnatts);
 
+       /* Non-key attributes don't have an opclass */
+       if (attno > rd_index->indnkeyatts)
+       {
+               ReleaseSysCache(tuple);
+               return InvalidOid;
+       }
+
        datum = SysCacheGetAttr(INDEXRELID, tuple,
                                                        Anum_pg_index_indclass, &isnull);
        Assert(!isnull);
 
        indclass = ((oidvector *) DatumGetPointer(datum));
+
+       Assert(attno <= indclass->dim1);
        opclass = indclass->values[attno - 1];
 
        ReleaseSysCache(tuple);