Minimal infrastructure for per-backend citus initialization.

src/backend/distributed/shared_library_init.c

@@ -1,7 +1,7 @@
 /*-------------------------------------------------------------------------
  *
  * shared_library_init.c
- *	  Initialize Citus extension
+ *	  Functionality related to the initialization of the Citus extension.
  *
  * Copyright (c) 2012-2016, Citus Data, Inc.
  *-------------------------------------------------------------------------
@@ -36,6 +36,7 @@
 #include "distributed/pg_dist_partition.h"
 #include "distributed/placement_connection.h"
 #include "distributed/remote_commands.h"
+#include "distributed/shared_library_init.h"
 #include "distributed/task_tracker.h"
 #include "distributed/transaction_management.h"
 #include "distributed/worker_manager.h"
@@ -177,6 +178,20 @@ _PG_init(void)
 }
 
 
+/*
+ * StartupCitusBackend initializes per-backend infrastructure, and is called
+ * the first time citus is used in a database.
+ *
+ * NB: All code here has to be able to cope with this routine being called
+ * multiple times in the same backend.  This will e.g. happen when the
+ * extension is created or upgraded.
+ */
+void
+StartupCitusBackend(void)
+{
+}
+
+
 /*
  * CreateRequiredDirectories - Create directories required for Citus to
  * function.

src/backend/distributed/utils/metadata_cache.c

@@ -35,6 +35,7 @@
 #include "distributed/pg_dist_partition.h"
 #include "distributed/pg_dist_shard.h"
 #include "distributed/pg_dist_shard_placement.h"
+#include "distributed/shared_library_init.h"
 #include "distributed/shardinterval_utils.h"
 #include "distributed/worker_manager.h"
 #include "distributed/worker_protocol.h"
@@ -1118,6 +1119,13 @@ CitusHasBeenLoaded(void)
 			{
 				extensionScriptExecuted = false;
 			}
+
+			/*
+			 * Whenever the extension exists, even when currently creating it,
+			 * we need the infrastructure to run citus in this database to be
+			 * ready.
+			 */
+			StartupCitusBackend();
 		}
 
 		/* we disable extension features during pg_upgrade */

src/include/distributed/shared_library_init.h

@@ -0,0 +1,16 @@
+/*-------------------------------------------------------------------------
+ *
+ * shared_library_init.h
+ *	  Functionality related to the initialization of the Citus extension.
+ *
+ * Copyright (c) 2017, Citus Data, Inc.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef SHARED_LIBRARY_INIT_H
+#define SHARED_LIBRARY_INIT_H
+
+extern void StartupCitusBackend(void);
+
+#endif /* SHARED_LIBRARY_INIT_H */