Introduce replication progress tracking infrastructure.

When implementing a replication solution ontop of logical decoding, two
related problems exist:
* How to safely keep track of replication progress
* How to change replication behavior, based on the origin of a row;
  e.g. to avoid loops in bi-directional replication setups

The solution to these problems, as implemented here, consist out of
three parts:

1) 'replication origins', which identify nodes in a replication setup.
2) 'replication progress tracking', which remembers, for each
   replication origin, how far replay has progressed in a efficient and
   crash safe manner.
3) The ability to filter out changes performed on the behest of a
   replication origin during logical decoding; this allows complex
   replication topologies. E.g. by filtering all replayed changes out.

Most of this could also be implemented in "userspace", e.g. by inserting
additional rows contain origin information, but that ends up being much
less efficient and more complicated.  We don't want to require various
replication solutions to reimplement logic for this independently. The
infrastructure is intended to be generic enough to be reusable.

This infrastructure also replaces the 'nodeid' infrastructure of commit
timestamps. It is intended to provide all the former capabilities,
except that there's only 2^16 different origins; but now they integrate
with logical decoding. Additionally more functionality is accessible via
SQL.  Since the commit timestamp infrastructure has also been introduced
in 9.5 (commit 73c986add) changing the API is not a problem.

For now the number of origins for which the replication progress can be
tracked simultaneously is determined by the max_replication_slots
GUC. That GUC is not a perfect match to configure this, but there
doesn't seem to be sufficient reason to introduce a separate new one.

Bumps both catversion and wal page magic.

Author: Andres Freund, with contributions from Petr Jelinek and Craig Ringer
Reviewed-By: Heikki Linnakangas, Petr Jelinek, Robert Haas, Steve Singer
Discussion: 20150216002155.GI15326@awork2.anarazel.de,
    20140923182422.GA15776@alap3.anarazel.de,
    20131114172632.GE7522@alap2.anarazel.de

4 files changed, 113 insertions, 1 deletions

diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index b36e4edd84..e8334025e1 100644
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201504261
+#define CATALOG_VERSION_NO	201504291
 
 #endif
diff --git a/src/include/catalog/indexing.h b/src/include/catalog/indexing.h
index a234bde293..71e0010a6f 100644
--- a/src/include/catalog/indexing.h
+++ b/src/include/catalog/indexing.h
@@ -310,6 +310,12 @@ DECLARE_UNIQUE_INDEX(pg_policy_oid_index, 3257, on pg_policy using btree(oid oid
 DECLARE_UNIQUE_INDEX(pg_policy_polrelid_polname_index, 3258, on pg_policy using btree(polrelid oid_ops, polname name_ops));
 #define PolicyPolrelidPolnameIndexId				3258
 
+DECLARE_UNIQUE_INDEX(pg_replication_origin_roiident_index, 6001, on pg_replication_origin using btree(roident oid_ops));
+#define ReplicationOriginIdentIndex 6001
+
+DECLARE_UNIQUE_INDEX(pg_replication_origin_roname_index, 6002, on pg_replication_origin using btree(roname varchar_pattern_ops));
+#define ReplicationOriginNameIndex 6002
+
 /* last step of initialization script: build the indexes declared above */
 BUILD_INDICES
 
diff --git a/src/include/catalog/pg_proc.h b/src/include/catalog/pg_proc.h
index e97e6b1944..55c246e73d 100644
--- a/src/include/catalog/pg_proc.h
+++ b/src/include/catalog/pg_proc.h
@@ -5203,6 +5203,42 @@ DESCR("for use by pg_upgrade");
 DATA(insert OID = 3591 ( binary_upgrade_create_empty_extension PGNSP PGUID  12 1 0 0 0 f f f f f f v 7 0 2278 "25 25 16 25 1028 1009 1009" _null_ _null_ _null_ _null_ _null_ binary_upgrade_create_empty_extension _null_ _null_ _null_ ));
 DESCR("for use by pg_upgrade");
 
+/* replication/origin.h */
+DATA(insert OID = 6003 ( pg_replication_origin_create PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 26 "25" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_create _null_ _null_ _null_ ));
+DESCR("create a replication origin");
+
+DATA(insert OID = 6004 ( pg_replication_origin_drop PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "25" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_drop _null_ _null_ _null_ ));
+DESCR("drop replication origin identified by its name");
+
+DATA(insert OID = 6005 ( pg_replication_origin_oid PGNSP PGUID 12 1 0 0 0 f f f f t f s 1 0 26 "25" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_oid _null_ _null_ _null_ ));
+DESCR("translate the replication origin's name to its id");
+
+DATA(insert OID = 6006 ( pg_replication_origin_session_setup PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 2278 "25" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_session_setup _null_ _null_ _null_ ));
+DESCR("configure session to maintain replication progress tracking for the passed in origin");
+
+DATA(insert OID = 6007 ( pg_replication_origin_session_reset PGNSP PGUID 12 1 0 0 0 f f f f t f v 0 0 2278 "" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_session_reset _null_ _null_ _null_ ));
+DESCR("teardown configured replication progress tracking");
+
+DATA(insert OID = 6008 ( pg_replication_origin_session_is_setup PGNSP PGUID 12 1 0 0 0 f f f f t f v 0 0 16 "" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_session_is_setup _null_ _null_ _null_ ));
+DESCR("is a replication origin configured in this session");
+
+DATA(insert OID = 6009 ( pg_replication_origin_session_progress PGNSP PGUID 12 1 0 0 0 f f f f t f v 1 0 3220 "16" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_session_progress _null_ _null_ _null_ ));
+DESCR("get the replication progress of the current session");
+
+DATA(insert OID = 6010 ( pg_replication_origin_xact_setup PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 2278 "3220 1184" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_xact_setup _null_ _null_ _null_ ));
+DESCR("setup the transaction's origin lsn and timestamp");
+
+DATA(insert OID = 6011 ( pg_replication_origin_xact_reset PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 2278 "3220 1184" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_xact_reset _null_ _null_ _null_ ));
+DESCR("reset the transaction's origin lsn and timestamp");
+
+DATA(insert OID = 6012 ( pg_replication_origin_advance PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 2278 "25 3220" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_advance _null_ _null_ _null_ ));
+DESCR("advance replication itentifier to specific location");
+
+DATA(insert OID = 6013 ( pg_replication_origin_progress PGNSP PGUID 12 1 0 0 0 f f f f t f v 2 0 3220 "25 16" _null_ _null_ _null_ _null_ _null_ pg_replication_origin_progress _null_ _null_ _null_ ));
+DESCR("get an individual replication origin's replication progress");
+
+DATA(insert OID = 6014 ( pg_show_replication_origin_status PGNSP PGUID 12 1 100 0 0 f f f f f t v 0 0 2249 "" "{26,25,3220,3220}" "{o,o,o,o}" "{local_id, external_id, remote_lsn, local_lsn}" _null_ _null_ pg_show_replication_origin_status _null_ _null_ _null_ ));
+DESCR("get progress for all replication origins");
 
 /*
  * Symbolic values for provolatile column: these indicate whether the result
diff --git a/src/include/catalog/pg_replication_origin.h b/src/include/catalog/pg_replication_origin.h
new file mode 100644
index 0000000000..3483809034
--- /dev/null
+++ b/src/include/catalog/pg_replication_origin.h
@@ -0,0 +1,70 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_replication_origin.h
+ *	  Persistent replication origin registry
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/catalog/pg_replication_origin.h
+ *
+ * NOTES
+ *	  the genbki.pl script reads this file and generates .bki
+ *	  information from the DATA() statements.
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef PG_REPLICATION_ORIGIN_H
+#define PG_REPLICATION_ORIGIN_H
+
+#include "catalog/genbki.h"
+#include "access/xlogdefs.h"
+
+/* ----------------
+ *		pg_replication_origin.  cpp turns this into
+ *		typedef struct FormData_pg_replication_origin
+ * ----------------
+ */
+#define ReplicationOriginRelationId 6000
+
+CATALOG(pg_replication_origin,6000) BKI_SHARED_RELATION BKI_WITHOUT_OIDS
+{
+	/*
+	 * Locally known id that get included into WAL.
+	 *
+	 * This should never leave the system.
+	 *
+	 * Needs to fit into a uint16, so we don't waste too much space in WAL
+	 * records. For this reason we don't use a normal Oid column here, since
+	 * we need to handle allocation of new values manually.
+	 */
+	Oid		roident;
+
+	/*
+	 * Variable-length fields start here, but we allow direct access to
+	 * roname.
+	 */
+
+	/* external, free-format, name */
+	text	roname BKI_FORCE_NOT_NULL;
+
+#ifdef CATALOG_VARLEN		/* further variable-length fields */
+#endif
+} FormData_pg_replication_origin;
+
+typedef FormData_pg_replication_origin *Form_pg_replication_origin;
+
+/* ----------------
+ *		compiler constants for pg_replication_origin
+ * ----------------
+ */
+#define Natts_pg_replication_origin					2
+#define Anum_pg_replication_origin_roident			1
+#define Anum_pg_replication_origin_roname			2
+
+/* ----------------
+ *		pg_replication_origin has no initial contents
+ * ----------------
+ */
+
+#endif   /* PG_REPLICATION_ORIGIN_H */