1 files changed, 123 insertions, 1 deletions

diff --git a/src/backend/access/transam/rmgr.c b/src/backend/access/transam/rmgr.c
index f8847d5aebf..3c2dc1000db 100644
--- a/src/backend/access/transam/rmgr.c
+++ b/src/backend/access/transam/rmgr.c
@@ -24,16 +24,138 @@
 #include "commands/dbcommands_xlog.h"
 #include "commands/sequence.h"
 #include "commands/tablespace.h"
+#include "fmgr.h"
+#include "funcapi.h"
+#include "miscadmin.h"
 #include "replication/decode.h"
 #include "replication/message.h"
 #include "replication/origin.h"
 #include "storage/standby.h"
+#include "utils/builtins.h"
 #include "utils/relmapper.h"
 
 /* must be kept in sync with RmgrData definition in xlog_internal.h */
 #define PG_RMGR(symname,name,redo,desc,identify,startup,cleanup,mask,decode) \
 	{ name, redo, desc, identify, startup, cleanup, mask, decode },
 
-const RmgrData RmgrTable[RM_MAX_ID + 1] = {
+RmgrData RmgrTable[RM_MAX_ID + 1] = {
 #include "access/rmgrlist.h"
 };
+
+/*
+ * Start up all resource managers.
+ */
+void
+RmgrStartup(void)
+{
+	for (int rmid = 0; rmid <= RM_MAX_ID; rmid++)
+	{
+		if (!RmgrIdExists(rmid))
+			continue;
+
+		if (RmgrTable[rmid].rm_startup != NULL)
+			RmgrTable[rmid].rm_startup();
+	}
+}
+
+/*
+ * Clean up all resource managers.
+ */
+void
+RmgrCleanup(void)
+{
+	for (int rmid = 0; rmid <= RM_MAX_ID; rmid++)
+	{
+		if (!RmgrIdExists(rmid))
+			continue;
+
+		if (RmgrTable[rmid].rm_cleanup != NULL)
+			RmgrTable[rmid].rm_cleanup();
+	}
+}
+
+/*
+ * Emit ERROR when we encounter a record with an RmgrId we don't
+ * recognize.
+ */
+void
+RmgrNotFound(RmgrId rmid)
+{
+	ereport(ERROR, (errmsg("resource manager with ID %d not registered", rmid),
+					errhint("Include the extension module that implements this resource manager in shared_preload_libraries.")));
+}
+
+/*
+ * Register a new custom WAL resource manager.
+ *
+ * Resource manager IDs must be globally unique across all extensions. Refer
+ * to https://wiki.postgresql.org/wiki/CustomWALResourceManager to reserve a
+ * unique RmgrId for your extension, to avoid conflicts with other extension
+ * developers. During development, use RM_EXPERIMENTAL_ID to avoid needlessly
+ * reserving a new ID.
+ */
+void
+RegisterCustomRmgr(RmgrId rmid, RmgrData *rmgr)
+{
+	if (rmgr->rm_name == NULL || strlen(rmgr->rm_name) == 0)
+		ereport(ERROR, (errmsg("custom resource manager name is invalid"),
+						errhint("Provide a non-empty name for the custom resource manager.")));
+
+	if (!RMID_IS_CUSTOM(rmid))
+		ereport(ERROR, (errmsg("custom resource manager ID %d is out of range", rmid),
+						errhint("Provide a custom resource manager ID between %d and %d.",
+								RM_MIN_CUSTOM_ID, RM_MAX_CUSTOM_ID)));
+
+	if (!process_shared_preload_libraries_in_progress)
+		ereport(ERROR,
+				(errmsg("failed to register custom resource manager \"%s\" with ID %d", rmgr->rm_name, rmid),
+				 errdetail("Custom resource manager must be registered while initializing modules in shared_preload_libraries.")));
+
+	if (RmgrTable[rmid].rm_name != NULL)
+		ereport(ERROR,
+				(errmsg("failed to register custom resource manager \"%s\" with ID %d", rmgr->rm_name, rmid),
+				 errdetail("Custom resource manager \"%s\" already registered with the same ID.",
+						   RmgrTable[rmid].rm_name)));
+
+	/* check for existing rmgr with the same name */
+	for (int existing_rmid = 0; existing_rmid <= RM_MAX_ID; existing_rmid++)
+	{
+		if (!RmgrIdExists(existing_rmid))
+			continue;
+
+		if (!pg_strcasecmp(RmgrTable[existing_rmid].rm_name, rmgr->rm_name))
+			ereport(ERROR,
+				(errmsg("failed to register custom resource manager \"%s\" with ID %d", rmgr->rm_name, rmid),
+				 errdetail("Existing resource manager with ID %d has the same name.", existing_rmid)));
+	}
+
+	/* register it */
+	RmgrTable[rmid] = *rmgr;
+	ereport(LOG,
+			(errmsg("registered custom resource manager \"%s\" with ID %d",
+					rmgr->rm_name, rmid)));
+}
+
+/* SQL SRF showing loaded resource managers */
+Datum
+pg_get_wal_resource_managers(PG_FUNCTION_ARGS)
+{
+#define PG_GET_RESOURCE_MANAGERS_COLS 3
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+	Datum		values[PG_GET_RESOURCE_MANAGERS_COLS];
+	bool		nulls[PG_GET_RESOURCE_MANAGERS_COLS] = {0};
+
+	SetSingleFuncCall(fcinfo, 0);
+
+	for (int rmid = 0; rmid <= RM_MAX_ID; rmid++)
+	{
+		if (!RmgrIdExists(rmid))
+			continue;
+		values[0] = Int32GetDatum(rmid);
+		values[1] = CStringGetTextDatum(GetRmgr(rmid).rm_name);
+		values[2] = BoolGetDatum(RMID_IS_BUILTIN(rmid));
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+	}
+
+	return (Datum) 0;
+}