Fix possible sorting error when aborting use of abbreviated keys.

Due to an error in the abbreviated key abort logic, the most recently
processed SortTuple could be incorrectly marked NULL, resulting in an
incorrect final sort order.

In the worst case, this could result in a corrupt btree index, which
would need to be rebuild using REINDEX.  However, abbrevation doesn't
abort very often, not all data types use it, and only one tuple would
end up in the wrong place, so the practical impact of this mistake may
be somewhat limited.

Report and patch by Peter Geoghegan.

diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 510565c339e49272d71b7ec1ef6d7a2f2210d8bc..ae384a8546ac450018b63e04154a40afa6c97f29 100644 (file)
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -1443,7 +1443,7 @@ tuplesort_putindextuplevalues(Tuplesortstate *state, Relation rel,
                        mtup->datum1 = index_getattr(tuple,
                                                                                 1,
                                                                                 RelationGetDescr(state->indexRel),
-                                                                                &stup.isnull1);
+                                                                                &mtup->isnull1);
                }
        }
 
@@ -4271,7 +4271,7 @@ copytup_cluster(Tuplesortstate *state, SortTuple *stup, void *tup)
                        mtup->datum1 = heap_getattr(tuple,
                                                                          state->indexInfo->ii_KeyAttrNumbers[0],
                                                                                state->tupDesc,
-                                                                               &stup->isnull1);
+                                                                               &mtup->isnull1);
                }
        }
 }
@@ -4588,7 +4588,7 @@ copytup_index(Tuplesortstate *state, SortTuple *stup, void *tup)
                        mtup->datum1 = index_getattr(tuple,
                                                                                 1,
                                                                                 RelationGetDescr(state->indexRel),
-                                                                                &stup->isnull1);
+                                                                                &mtup->isnull1);
                }
        }
 }