Add optional pid parameter to pg_replication_origin_session_setup().

Commit 216a784829c introduced parallel apply workers, allowing multiple
processes to share a replication origin. To support this,
replorigin_session_setup() was extended to accept a pid argument
identifying the process using the origin.

This commit exposes that capability through the SQL interface function
pg_replication_origin_session_setup() by adding an optional pid parameter.
This enables multiple processes to coordinate replication using the same
origin when using SQL-level replication functions.

This change allows the non-builtin logical replication solutions to
implement parallel apply for large transactions.

Additionally, an existing internal error was made user-facing, as it can
now be triggered via the exposed SQL API.

Author: Doruk Yilmaz <doruk@mixrank.com>
Author: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Euler Taveira <euler@eulerto.com>
Discussion: https://postgr.es/m/CAMPB6wfe4zLjJL8jiZV5kjjpwBM2=rTRme0UCL7Ra4L8MTVdOg@mail.gmail.com
Discussion: https://postgr.es/m/CAE2gYzyTSNvHY1+iWUwykaLETSuAZsCWyryokjP6rG46ZvRgQA@mail.gmail.com

contrib/test_decoding/Makefile

@@ -9,7 +9,7 @@ REGRESS = ddl xact rewrite toast permissions decoding_in_xact \
 ISOLATION = mxact delayed_startup ondisk_startup concurrent_ddl_dml \
 	oldest_xmin snapshot_transfer subxact_without_top concurrent_stream \
 	twophase_snapshot slot_creation_error catalog_change_snapshot \
-	skip_snapshot_restore invalidation_distribution
+	skip_snapshot_restore invalidation_distribution parallel_session_origin
 
 REGRESS_OPTS = --temp-config $(top_srcdir)/contrib/test_decoding/logical.conf
 ISOLATION_OPTS = --temp-config $(top_srcdir)/contrib/test_decoding/logical.conf

contrib/test_decoding/expected/parallel_session_origin.out

@@ -0,0 +1,79 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s0_setup s0_is_setup s1_setup s1_is_setup s0_add_message s0_store_lsn s1_add_message s1_store_lsn s0_compare s0_reset s1_reset
+step s0_setup: SELECT pg_replication_origin_session_setup('origin');
+pg_replication_origin_session_setup
+-----------------------------------
+                                   
+(1 row)
+
+step s0_is_setup: SELECT pg_replication_origin_session_is_setup();
+pg_replication_origin_session_is_setup
+--------------------------------------
+t                                     
+(1 row)
+
+step s1_setup: 
+    SELECT pg_replication_origin_session_setup('origin', pid)
+    FROM pg_stat_activity
+    WHERE application_name = 'isolation/parallel_session_origin/s0';
+
+pg_replication_origin_session_setup
+-----------------------------------
+                                   
+(1 row)
+
+step s1_is_setup: SELECT pg_replication_origin_session_is_setup();
+pg_replication_origin_session_is_setup
+--------------------------------------
+t                                     
+(1 row)
+
+step s0_add_message: 
+    SELECT 1
+    FROM pg_logical_emit_message(true, 'prefix', 'message on s0');
+
+?column?
+--------
+       1
+(1 row)
+
+step s0_store_lsn: 
+    INSERT INTO local_lsn_store
+    SELECT 0, local_lsn FROM pg_replication_origin_status;
+
+step s1_add_message: 
+    SELECT 1
+    FROM pg_logical_emit_message(true, 'prefix', 'message on s1');
+
+?column?
+--------
+       1
+(1 row)
+
+step s1_store_lsn: 
+    INSERT INTO local_lsn_store
+    SELECT 1, local_lsn FROM pg_replication_origin_status;
+
+step s0_compare: 
+    SELECT s0.lsn < s1.lsn
+    FROM local_lsn_store as s0, local_lsn_store as s1
+    WHERE s0.session = 0 AND s1.session = 1;
+
+?column?
+--------
+t       
+(1 row)
+
+step s0_reset: SELECT pg_replication_origin_session_reset();
+pg_replication_origin_session_reset
+-----------------------------------
+                                   
+(1 row)
+
+step s1_reset: SELECT pg_replication_origin_session_reset();
+pg_replication_origin_session_reset
+-----------------------------------
+                                   
+(1 row)
+

contrib/test_decoding/expected/replorigin.out

@@ -41,6 +41,9 @@ SELECT pg_replication_origin_create('regress_test_decoding: regression_slot');
 SELECT pg_replication_origin_create('regress_test_decoding: regression_slot');
 ERROR:  duplicate key value violates unique constraint "pg_replication_origin_roname_index"
 DETAIL:  Key (roname)=(regress_test_decoding: regression_slot) already exists.
+-- ensure inactive origin cannot be set as session one if pid is specified
+SELECT pg_replication_origin_session_setup('regress_test_decoding: regression_slot', -1);
+ERROR:  cannot use PID -1 for inactive replication origin with ID 1
 --ensure deletions work (once)
 SELECT pg_replication_origin_create('regress_test_decoding: temp');
  pg_replication_origin_create 

contrib/test_decoding/meson.build

@@ -64,6 +64,7 @@ tests += {
       'slot_creation_error',
       'skip_snapshot_restore',
       'invalidation_distribution',
+      'parallel_session_origin',
     ],
     'regress_args': [
       '--temp-config', files('logical.conf'),

contrib/test_decoding/specs/parallel_session_origin.spec

@@ -0,0 +1,56 @@
+# Test parallel replication origin manipulations; ensure local_lsn can be
+# updated by all attached sessions.
+
+setup
+{
+    SELECT pg_replication_origin_create('origin');
+    CREATE UNLOGGED TABLE local_lsn_store (session int, lsn pg_lsn);
+}
+
+teardown
+{
+    SELECT pg_replication_origin_drop('origin');
+    DROP TABLE local_lsn_store;
+}
+
+session "s0"
+setup { SET synchronous_commit = on; }
+step "s0_setup" { SELECT pg_replication_origin_session_setup('origin'); }
+step "s0_is_setup" { SELECT pg_replication_origin_session_is_setup(); }
+step "s0_add_message" {
+    SELECT 1
+    FROM pg_logical_emit_message(true, 'prefix', 'message on s0');
+}
+step "s0_store_lsn" {
+    INSERT INTO local_lsn_store
+    SELECT 0, local_lsn FROM pg_replication_origin_status;
+}
+step "s0_compare" {
+    SELECT s0.lsn < s1.lsn
+    FROM local_lsn_store as s0, local_lsn_store as s1
+    WHERE s0.session = 0 AND s1.session = 1;
+}
+step "s0_reset" { SELECT pg_replication_origin_session_reset(); }
+
+session "s1"
+setup { SET synchronous_commit = on; }
+step "s1_setup" {
+    SELECT pg_replication_origin_session_setup('origin', pid)
+    FROM pg_stat_activity
+    WHERE application_name = 'isolation/parallel_session_origin/s0';
+}
+step "s1_is_setup" { SELECT pg_replication_origin_session_is_setup(); }
+step "s1_add_message" {
+    SELECT 1
+    FROM pg_logical_emit_message(true, 'prefix', 'message on s1');
+}
+step "s1_store_lsn" {
+    INSERT INTO local_lsn_store
+    SELECT 1, local_lsn FROM pg_replication_origin_status;
+}
+step "s1_reset" { SELECT pg_replication_origin_session_reset(); }
+
+# Firstly s0 attaches to a origin and s1 attaches to the same. Both sessions
+# commits a transaction and store the local_lsn of the replication origin.
+# Compare LSNs and expect latter transaction (done by s1) has larger local_lsn.
+permutation "s0_setup" "s0_is_setup" "s1_setup" "s1_is_setup" "s0_add_message" "s0_store_lsn" "s1_add_message" "s1_store_lsn" "s0_compare" "s0_reset" "s1_reset"

contrib/test_decoding/sql/replorigin.sql

@@ -26,6 +26,9 @@ SELECT pg_replication_origin_create('regress_test_decoding: regression_slot');
 -- ensure duplicate creations fail
 SELECT pg_replication_origin_create('regress_test_decoding: regression_slot');
 
+-- ensure inactive origin cannot be set as session one if pid is specified
+SELECT pg_replication_origin_session_setup('regress_test_decoding: regression_slot', -1);
+
 --ensure deletions work (once)
 SELECT pg_replication_origin_create('regress_test_decoding: temp');
 SELECT pg_replication_origin_drop('regress_test_decoding: temp');

doc/src/sgml/func/func-admin.sgml

@@ -1315,7 +1315,7 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset
         <indexterm>
          <primary>pg_replication_origin_session_setup</primary>
         </indexterm>
-        <function>pg_replication_origin_session_setup</function> ( <parameter>node_name</parameter> <type>text</type> )
+        <function>pg_replication_origin_session_setup</function> ( <parameter>node_name</parameter> <type>text</type> <optional>, <parameter>pid</parameter> <type>integer</type> <literal>DEFAULT</literal> <literal>0</literal></optional> )
         <returnvalue>void</returnvalue>
        </para>
        <para>
@@ -1323,7 +1323,26 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset
         origin, allowing replay progress to be tracked.
         Can only be used if no origin is currently selected.
         Use <function>pg_replication_origin_session_reset</function> to undo.
-       </para></entry>
+        If multiple processes can safely use the same replication origin (for
+        example, parallel apply processes), the optional <parameter>pid</parameter>
+        parameter can be used to specify the process ID of the first process.
+        The first process must provide <parameter>pid</parameter> equals to
+        <literal>0</literal> and the other processes that share the same
+        replication origin should provide the process ID of the first process.
+       </para>
+       <caution>
+        <para>
+         When multiple processes share the same replication origin, it is critical
+         to maintain commit order to prevent data inconsistency. While processes
+         may send operations out of order, they must commit transactions in the
+         correct sequence to ensure proper replication consistency. The recommended workflow
+         for each worker is: set up the replication origin session with the first process's PID,
+         apply changes within transactions, call <function>pg_replication_origin_xact_setup</function>
+         with the LSN and commit timestamp before committing, then commit the
+         transaction only if everything succeeded.
+        </para>
+       </caution>
+      </entry>
       </row>
 
       <row>

src/backend/catalog/system_functions.sql

@@ -650,6 +650,13 @@ LANGUAGE INTERNAL
 CALLED ON NULL INPUT VOLATILE PARALLEL SAFE
 AS 'pg_stat_reset_slru';
 
+CREATE OR REPLACE FUNCTION
+  pg_replication_origin_session_setup(node_name text, pid integer DEFAULT 0)
+RETURNS void
+LANGUAGE INTERNAL
+STRICT VOLATILE PARALLEL UNSAFE
+AS 'pg_replication_origin_session_setup';
+
 --
 -- The default permissions for functions mean that anyone can execute them.
 -- A number of functions shouldn't be executable by just anyone, but rather
@@ -751,7 +758,7 @@ REVOKE EXECUTE ON FUNCTION pg_replication_origin_session_progress(boolean) FROM
 
 REVOKE EXECUTE ON FUNCTION pg_replication_origin_session_reset() FROM public;
 
-REVOKE EXECUTE ON FUNCTION pg_replication_origin_session_setup(text) FROM public;
+REVOKE EXECUTE ON FUNCTION pg_replication_origin_session_setup(text, integer) FROM public;
 
 REVOKE EXECUTE ON FUNCTION pg_replication_origin_xact_reset() FROM public;
 

src/backend/replication/logical/origin.c

@@ -1167,6 +1167,14 @@ replorigin_session_setup(RepOriginId node, int acquired_by)
 							curstate->roident, curstate->acquired_by)));
 		}
 
+		else if (curstate->acquired_by != acquired_by)
+		{
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_IN_USE),
+					 errmsg("could not find replication state slot for replication origin with OID %u which was acquired by %d",
+							node, acquired_by)));
+		}
+
 		/* ok, found slot */
 		session_replication_state = curstate;
 		break;
@@ -1181,6 +1189,12 @@ replorigin_session_setup(RepOriginId node, int acquired_by)
 				 errhint("Increase \"max_active_replication_origins\" and try again.")));
 	else if (session_replication_state == NULL)
 	{
+		if (acquired_by)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("cannot use PID %d for inactive replication origin with ID %d",
+							acquired_by, node)));
+
 		/* initialize new slot */
 		session_replication_state = &replication_states[free_slot];
 		Assert(session_replication_state->remote_lsn == InvalidXLogRecPtr);
@@ -1193,9 +1207,8 @@ replorigin_session_setup(RepOriginId node, int acquired_by)
 
 	if (acquired_by == 0)
 		session_replication_state->acquired_by = MyProcPid;
-	else if (session_replication_state->acquired_by != acquired_by)
-		elog(ERROR, "could not find replication state slot for replication origin with OID %u which was acquired by %d",
-			 node, acquired_by);
+	else
+		Assert(session_replication_state->acquired_by == acquired_by);
 
 	LWLockRelease(ReplicationOriginLock);
 
@@ -1374,12 +1387,14 @@ pg_replication_origin_session_setup(PG_FUNCTION_ARGS)
 {
 	char	   *name;
 	RepOriginId origin;
+	int			pid;
 
 	replorigin_check_prerequisites(true, false);
 
 	name = text_to_cstring((text *) DatumGetPointer(PG_GETARG_DATUM(0)));
 	origin = replorigin_by_name(name, false);
-	replorigin_session_setup(origin, 0);
+	pid = PG_GETARG_INT32(1);
+	replorigin_session_setup(origin, pid);
 
 	replorigin_session_origin = origin;
 

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202509091
+#define CATALOG_VERSION_NO	202509191
 
 #endif

src/include/catalog/pg_proc.dat

@@ -12235,7 +12235,7 @@
 { oid => '6006',
   descr => 'configure session to maintain replication progress tracking for the passed in origin',
   proname => 'pg_replication_origin_session_setup', provolatile => 'v',
-  proparallel => 'u', prorettype => 'void', proargtypes => 'text',
+  proparallel => 'u', prorettype => 'void', proargtypes => 'text int4',
   prosrc => 'pg_replication_origin_session_setup' },
 
 { oid => '6007', descr => 'teardown configured replication progress tracking',