Merge lp:~lifeless/launchpad/bug-121363 into lp:launchpad/db-devel

[Robert Collins]

Permit bug searches ordered by date_closed desc, id to come from index.

Permit bug searches ordered by date_closed desc, id to come from index.

[Robert Collins (lifeless)]

If the existing index is actually being used to order other queries, we could just add the new one.

[Stuart Bishop (stub)]

The CREATE INDEX needs to be in a separate patch because we will be applying it live. patch-2208-08-3.sql.

The DROP INDEX can go in patch-2208-15-0.sql

review: Approve (db)

=== added file 'database/schema/patch-2208-08-3.sql'
--- database/schema/patch-2208-08-3.sql	1970-01-01 00:00:00 +0000
+++ database/schema/patch-2208-08-3.sql	2010-09-20 02:15:58 +0000
@@ -0,0 +1,8 @@
+SET client_min_messages=ERROR;
+
+-- Permit bug searches ordered by 'date_closed desc, id' to serve from
+-- index rather than doing the full search and sorting.
+
+CREATE INDEX bugtask__date_closed__id__idx2 ON BugTask (date_closed, id desc nulls first);
+
+INSERT INTO LaunchpadDatabaseRevision VALUES (2208, 8, 3);

=== added file 'database/schema/patch-2208-15-0.sql'
--- database/schema/patch-2208-15-0.sql	1970-01-01 00:00:00 +0000
+++ database/schema/patch-2208-15-0.sql	2010-09-20 02:15:58 +0000
@@ -0,0 +1,7 @@
+SET client_min_messages=ERROR;
+
+-- Delete index obsoleted by bugtask__date_closed__id__idx2
+
+DROP INDEX bugtask__date_closed__id__idx;
+
+INSERT INTO LaunchpadDatabaseRevision VALUES (2208, 15, 0);