diff options
Diffstat (limited to 'src/backend/optimizer/path/pathkeys.c')
| -rw-r--r-- | src/backend/optimizer/path/pathkeys.c | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/src/backend/optimizer/path/pathkeys.c b/src/backend/optimizer/path/pathkeys.c index 4216768212c..dc7687916f6 100644 --- a/src/backend/optimizer/path/pathkeys.c +++ b/src/backend/optimizer/path/pathkeys.c @@ -11,7 +11,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.74 2005/11/22 18:17:12 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/pathkeys.c,v 1.75 2006/01/29 17:27:42 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -909,13 +909,20 @@ get_cheapest_fractional_path_for_pathkeys(List *paths, * If 'scandir' is BackwardScanDirection, attempt to build pathkeys * representing a backwards scan of the index. Return NIL if can't do it. * + * If 'canonical' is TRUE, we remove duplicate pathkeys (which can occur + * if two index columns are equijoined, eg WHERE x = 1 AND y = 1). This + * is required if the result is to be compared directly to a canonical query + * pathkeys list. However, some callers want a list with exactly one entry + * per index column, and they must pass FALSE. + * * We generate the full pathkeys list whether or not all are useful for the * current query. Caller should do truncate_useless_pathkeys(). */ List * build_index_pathkeys(PlannerInfo *root, IndexOptInfo *index, - ScanDirection scandir) + ScanDirection scandir, + bool canonical) { List *retval = NIL; int *indexkeys = index->indexkeys; @@ -956,11 +963,11 @@ build_index_pathkeys(PlannerInfo *root, item = makePathKeyItem(indexkey, sortop, true); cpathkey = make_canonical_pathkey(root, item); - /* - * Eliminate redundant ordering info; could happen if query is such - * that index keys are equijoined... - */ - retval = list_append_unique_ptr(retval, cpathkey); + /* Eliminate redundant ordering info if requested */ + if (canonical) + retval = list_append_unique_ptr(retval, cpathkey); + else + retval = lappend(retval, cpathkey); indexkeys++; ordering++; |