make load_config() return status, rework pg_pathman's utility relations (e.g. pathman_config) Oid cache

funbringer · funbringer · commit e5ad13457c64 · 2016-08-19T20:17:21.000+03:00
diff --git a/src/init.c b/src/init.c
@@ -53,6 +53,8 @@ bool			initialization_needed = true;
 static bool		relcache_callback_needed = true;
 
 
+static bool init_pathman_relation_oids(void);
+static void fini_pathman_relation_oids(void);
 static void init_local_cache(void);
 static void fini_local_cache(void);
 static void read_pathman_config(void);
@@ -79,12 +81,22 @@ static int oid_cmp(const void *p1, const void *p2);
 
 /*
  * Create local PartRelationInfo cache & load pg_pathman's config.
+ * Return true on success. May occasionally emit ERROR.
  */
-void
+bool
 load_config(void)
 {
-	/* Cache PATHMAN_CONFIG relation's Oid */
-	pathman_config_relid = get_relname_relid(PATHMAN_CONFIG, get_pathman_schema());
+	/*
+	 * Try to cache important relids.
+	 *
+	 * Once CREATE EXTENSION stmt is processed, get_pathman_schema()
+	 * function starts returning perfectly valid schema Oid, which
+	 * means we have to check that *ALL* pg_pathman's relations' Oids
+	 * have been cached properly. Only then can we assume that
+	 * initialization is not needed anymore.
+	 */
+	if (!init_pathman_relation_oids())
+		return false; /* remain 'uninitialized', exit before creating main caches */
 
 	init_local_cache();		/* create 'partitioned_rels' hash table */
 	read_pathman_config();	/* read PATHMAN_CONFIG table & fill cache */
@@ -100,6 +112,8 @@ load_config(void)
 	initialization_needed = false;
 
 	elog(DEBUG2, "pg_pathman's config has been loaded successfully [%u]", MyProcPid);
+
+	return true;
 }
 
 /*
@@ -108,10 +122,11 @@ load_config(void)
 void
 unload_config(void)
 {
-	/* Don't forget to reset cached PATHMAN_CONFIG relation's Oid */
-	pathman_config_relid = InvalidOid;
+	/* Don't forget to reset pg_pathman's cached relids */
+	fini_pathman_relation_oids();
 
-	fini_local_cache();		/* destroy 'partitioned_rels' hash table */
+	/* Destroy 'partitioned_rels' & 'parent_cache' hash tables */
+	fini_local_cache();
 
 	/* Mark pg_pathman as uninitialized */
 	initialization_needed = true;
@@ -128,6 +143,40 @@ estimate_pathman_shmem_size(void)
 	return estimate_dsm_config_size() + MAXALIGN(sizeof(PathmanState));
 }
 
+/*
+ * Cache *all* important pg_pathman's relids at once.
+ * We should NOT rely on any previously cached values.
+ */
+static bool
+init_pathman_relation_oids(void)
+{
+	Oid schema = get_pathman_schema();
+	Assert(schema != InvalidOid);
+
+	/* Cache PATHMAN_CONFIG relation's Oid */
+	pathman_config_relid = get_relname_relid(PATHMAN_CONFIG, schema);
+	/* NOTE: add more relations to be cached right here ^^^ */
+
+	/* Return false if *any* relation doesn't exist yet */
+	if (pathman_config_relid == InvalidOid)
+	{
+		return false;
+	}
+
+	/* Everything is fine, proceed */
+	return true;
+}
+
+/*
+ * Forget *all* pg_pathman's cached relids.
+ */
+static void
+fini_pathman_relation_oids(void)
+{
+	pathman_config_relid = InvalidOid;
+	/* NOTE: add more relations to be forgotten right here ^^^ */
+}
+
 /*
  * Initialize per-process resources.
  */
diff --git a/src/init.h b/src/init.h
@@ -26,7 +26,7 @@ extern bool		initialization_needed;
 
 Size estimate_pathman_shmem_size(void);
 void init_shmem_config(void);
-void load_config(void);
+bool load_config(void);
 void unload_config(void);
 
 void fill_prel_with_partitions(const Oid *partitions,
diff --git a/src/worker.c b/src/worker.c
@@ -104,9 +104,13 @@ UnpackDatumFromByteArray(Datum *datum, Size datum_size, bool typbyval,
 static void
 bg_worker_load_config(const char *bgw_name)
 {
-	load_config();
-	elog(LOG, "%s: loaded pg_pathman's config [%u]",
-		 bgw_name, MyProcPid);
+	/* Try to load config */
+	if (!load_config())
+		elog(ERROR, "%s: could not load pg_pathman's config [%u]",
+			 bgw_name, MyProcPid);
+	else
+		elog(LOG, "%s: loaded pg_pathman's config [%u]",
+			 bgw_name, MyProcPid);
 }
 
 /*
