Make GIN and GIST pass the index collation to all their support functions.

Experimentation with contrib/btree_gist shows that the majority of the GIST
support functions potentially need collation information.  Safest policy
seems to be to pass it to all of them, instead of making assumptions about
which ones could possibly need it.

1 files changed, 17 insertions, 0 deletions

diff --git a/src/backend/access/gist/gist.c b/src/backend/access/gist/gist.c
index fae3464600a..4881a7dd48b 100644
--- a/src/backend/access/gist/gist.c
+++ b/src/backend/access/gist/gist.c
@@ -17,6 +17,7 @@
 #include "access/genam.h"
 #include "access/gist_private.h"
 #include "catalog/index.h"
+#include "catalog/pg_collation.h"
 #include "miscadmin.h"
 #include "storage/bufmgr.h"
 #include "storage/indexfsm.h"
@@ -1394,6 +1395,22 @@ initGISTstate(GISTSTATE *giststate, Relation index)
 						   CurrentMemoryContext);
 		else
 			giststate->distanceFn[i].fn_oid = InvalidOid;
+
+		/*
+		 * If the index column has a specified collation, we should honor that
+		 * while doing comparisons.  However, we may have a collatable storage
+		 * type for a noncollatable indexed data type.  If there's no index
+		 * collation then specify default collation in case the support
+		 * functions need collation.  This is harmless if the support
+		 * functions don't care about collation, so we just do it
+		 * unconditionally.  (We could alternatively call get_typcollation,
+		 * but that seems like expensive overkill --- there aren't going to be
+		 * any cases where a GIST storage type has a nondefault collation.)
+		 */
+		if (OidIsValid(index->rd_indcollation[i]))
+			giststate->supportCollation[i] = index->rd_indcollation[i];
+		else
+			giststate->supportCollation[i] = DEFAULT_COLLATION_OID;
 	}
 }