add an index for replication job source replicassmh-replication-queue-source-index

The reconciler checks whether a replica is acting as a source of a
replication job prior to avoid breaking existing jobs when scheduling
'delete_replica' jobs. This commit adds an index for this check to ensure
it doesn't slow down linearly with then number of jobs in the replication
queue.

1 files changed, 22 insertions, 0 deletions

diff --git a/internal/praefect/datastore/migrations/20210223160555_replication_queue_source_index.go b/internal/praefect/datastore/migrations/20210223160555_replication_queue_source_index.go
new file mode 100644
index 000000000..fbf8ce3cf
--- /dev/null
+++ b/internal/praefect/datastore/migrations/20210223160555_replication_queue_source_index.go
@@ -0,0 +1,22 @@
+package migrations
+
+import migrate "github.com/rubenv/sql-migrate"
+
+func init() {
+	m := &migrate.Migration{
+		Id: "20210223160555_replication_queue_source_index",
+		Up: []string{
+			`CREATE INDEX CONCURRENTLY replication_queue_source_index
+ON replication_queue (
+	(job->>'virtual_storage'),
+	(job->>'relative_path'),
+	(job->>'source_node_storage')
+)
+WHERE state NOT IN ('completed', 'cancelled', 'dead')`,
+		},
+		Down:                 []string{"DROP INDEX replication_queue_source_index"},
+		DisableTransactionUp: true,
+	}
+
+	allMigrations = append(allMigrations, m)
+}