schema: Provide index on flights by start time

We often use flight number as a proxy for ordering, but this is not
always appropriate and not always done (and sometimes it's a bit of a
bodge).

Provide an index to find flights by start time.  This significantly
speeds up the host allocation $equivstatusq query, and the duration
estimator.

(I have tested this by creating a trial index in the production
database.  That index can be dropped again, preferably after this
commit makes it to production.)

Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

diff --git a/schema/flights-started-index.sql b/schema/flights-started-index.sql
new file mode 100644 (file)
index 0000000..c230d9d
--- /dev/null
+++ b/schema/flights-started-index.sql
@@ -0,0 +1,7 @@
+-- ##OSSTEST## 011 Harmless
+--
+-- This index helps ts-hosts-allocate-Executive find recent instances
+-- of the same job.  It may be useful for other things too.
+
+CREATE INDEX flights_blessing_started_idx
+    ON flights (blessing, started);