Custom WAL Resource Managers.

Allow extensions to specify a new custom resource manager (rmgr),
which allows specialized WAL. This is meant to be used by a Table
Access Method or Index Access Method.

Prior to this commit, only Generic WAL was available, which offers
support for recovery and physical replication but not logical
replication.

Reviewed-by: Julien Rouhaud, Bharath Rupireddy, Andres Freund
Discussion: https://postgr.es/m/ed1fb2e22d15d3563ae0eb610f7b61bb15999c0a.camel%40j-davis.com

6 files changed, 49 insertions, 4 deletions

diff --git a/src/include/access/rmgr.h b/src/include/access/rmgr.h
index d9b512630ca..d9a96410d97 100644
--- a/src/include/access/rmgr.h
+++ b/src/include/access/rmgr.h
@@ -30,6 +30,23 @@ typedef enum RmgrIds
 
 #undef PG_RMGR
 
-#define RM_MAX_ID				(RM_NEXT_ID - 1)
+#define RM_MAX_ID			UINT8_MAX
+#define RM_MAX_BUILTIN_ID	(RM_NEXT_ID - 1)
+#define RM_MIN_CUSTOM_ID	128
+#define RM_MAX_CUSTOM_ID	UINT8_MAX
+#define RM_N_IDS			(UINT8_MAX + 1)
+#define RM_N_BUILTIN_IDS	(RM_MAX_BUILTIN_ID + 1)
+#define RM_N_CUSTOM_IDS		(RM_MAX_CUSTOM_ID - RM_MIN_CUSTOM_ID + 1)
+#define RMID_IS_BUILTIN(rmid) ((rmid) <= RM_MAX_BUILTIN_ID)
+#define RMID_IS_CUSTOM(rmid) ((rmid) >= RM_MIN_CUSTOM_ID && \
+							  (rmid) <= RM_MAX_CUSTOM_ID)
+#define RMID_IS_VALID(rmid) (RMID_IS_BUILTIN((rmid)) || RMID_IS_CUSTOM((rmid)))
+
+/*
+ * RmgrId to use for extensions that require an RmgrId, but are still in
+ * development and have not reserved their own unique RmgrId yet. See:
+ * https://wiki.postgresql.org/wiki/CustomWALResourceManagers
+ */
+#define RM_EXPERIMENTAL_ID		128
 
 #endif							/* RMGR_H */
diff --git a/src/include/access/xlog_internal.h b/src/include/access/xlog_internal.h
index b7c375fed1c..f69ea2355da 100644
--- a/src/include/access/xlog_internal.h
+++ b/src/include/access/xlog_internal.h
@@ -304,7 +304,8 @@ struct XLogRecordBuffer;
  * rm_mask takes as input a page modified by the resource manager and masks
  * out bits that shouldn't be flagged by wal_consistency_checking.
  *
- * RmgrTable[] is indexed by RmgrId values (see rmgrlist.h).
+ * RmgrTable[] is indexed by RmgrId values (see rmgrlist.h). If rm_name is
+ * NULL, the corresponding RmgrTable entry is considered invalid.
  */
 typedef struct RmgrData
 {
@@ -319,7 +320,25 @@ typedef struct RmgrData
 							  struct XLogRecordBuffer *buf);
 } RmgrData;
 
-extern const RmgrData RmgrTable[];
+extern RmgrData RmgrTable[];
+extern void RmgrStartup(void);
+extern void RmgrCleanup(void);
+extern void RmgrNotFound(RmgrId rmid);
+extern void RegisterCustomRmgr(RmgrId rmid, RmgrData *rmgr);
+
+static inline bool
+RmgrIdExists(RmgrId rmid)
+{
+	return RmgrTable[rmid].rm_name != NULL;
+}
+
+static inline RmgrData
+GetRmgr(RmgrId rmid)
+{
+	if (unlikely(!RmgrIdExists(rmid)))
+		RmgrNotFound(rmid);
+	return RmgrTable[rmid];
+}
 
 /*
  * Exported to support xlog switching from checkpointer
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index b6742b12c52..19bb3a79b42 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202204071
+#define CATALOG_VERSION_NO	202204072
 
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index e8f89a7b180..0f0f41b2f92 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6356,6 +6356,13 @@
   prorettype => 'text', proargtypes => '',
   prosrc => 'pg_get_wal_replay_pause_state' },
 
+{ oid => '8189', descr => 'get resource managers loaded in system',
+  proname => 'pg_get_wal_resource_managers', prorows => '50', proretset => 't',
+  provolatile => 'v', prorettype => 'record', proargtypes => '',
+  proallargtypes => '{int4,text,bool}', proargmodes => '{o,o,o}',
+  proargnames => '{rm_id, rm_name, rm_builtin}',
+  prosrc => 'pg_get_wal_resource_managers' },
+
 { oid => '2621', descr => 'reload configuration files',
   proname => 'pg_reload_conf', provolatile => 'v', prorettype => 'bool',
   proargtypes => '', prosrc => 'pg_reload_conf' },
diff --git a/src/include/miscadmin.h b/src/include/miscadmin.h
index 66c404c666d..bcf20164212 100644
--- a/src/include/miscadmin.h
+++ b/src/include/miscadmin.h
@@ -465,6 +465,7 @@ extern void BaseInit(void);
 /* in utils/init/miscinit.c */
 extern bool IgnoreSystemIndexes;
 extern PGDLLIMPORT bool process_shared_preload_libraries_in_progress;
+extern bool process_shared_preload_libraries_done;
 extern char *session_preload_libraries_string;
 extern char *shared_preload_libraries_string;
 extern char *local_preload_libraries_string;
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 3446334e906..74018ea27bc 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -367,6 +367,7 @@ extern void ProcessConfigFile(GucContext context);
 extern char *convert_GUC_name_for_parameter_acl(const char *name);
 extern bool check_GUC_name_for_parameter_acl(const char *name);
 extern void InitializeGUCOptions(void);
+extern void InitializeWalConsistencyChecking(void);
 extern bool SelectConfigFiles(const char *userDoption, const char *progname);
 extern void ResetAllOptions(void);
 extern void AtStart_GUC(void);