Date: Mon, 28 Apr 2025 16:51:07 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Nisha Moond <nisha.moond412@gmail.com>,
	Euler Taveira <euler@eulerto.com>,
	Michael Paquier <michael@paquier.xyz>,
	Amit Kapila <amit.kapila16@gmail.com>,
	Alexander Lakhin <exclusion@gmail.com>,
	"Jonathan S. Katz" <jkatz@postgresql.org>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Large expressions in indexes can't be stored (non-TOASTable)
Message-ID: <aA_4S5ZBaI_Qje2s@nathan>
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On Mon, Apr 28, 2025 at 05:35:08PM -0400, Tom Lane wrote:
> Possibly better idea: can we add something like
> Assert(!OidIsValid(reltoastrelid)) in the code that is making this
> assumption?

Yeah, we could add something like that to replorigin_create() pretty
easily.  The comment for that would be even harder to miss.

-- 
nathan

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	filename="v6-0001-Remove-pg_replication_origin-s-TOAST-table.patch"

From 39f870e69aa0cb08c0ef653b60ff07fa020c6bba Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathan@postgresql.org>
Date: Mon, 28 Apr 2025 16:27:33 -0500
Subject: [PATCH v6 1/1] Remove pg_replication_origin's TOAST table.

Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Euler Taveira <euler@eulerto.com>
Reviewed-by: Nisha Moond <nisha.moond412@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/ZvMSUPOqUU-VNADN%40nathan
---
 doc/src/sgml/func.sgml                       |  1 +
 src/backend/catalog/catalog.c                |  2 --
 src/backend/replication/logical/origin.c     | 22 ++++++++++++++++++++
 src/include/catalog/pg_replication_origin.h  |  2 --
 src/include/replication/origin.h             |  7 +++++++
 src/test/regress/expected/misc_functions.out |  4 ++++
 src/test/regress/expected/misc_sanity.out    |  7 ++++++-
 src/test/regress/sql/misc_functions.sql      |  3 +++
 src/test/regress/sql/misc_sanity.sql         |  4 ++++
 9 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 574a544d9fa..593e45495be 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -29941,6 +29941,7 @@ postgres=# SELECT '0/0'::pg_lsn + pd.segment_number * ps.setting::int + :offset
        <para>
         Creates a replication origin with the given external
         name, and returns the internal ID assigned to it.
+        The name must be no longer than 512 bytes.
        </para></entry>
       </row>
 
diff --git a/src/backend/catalog/catalog.c b/src/backend/catalog/catalog.c
index 60000bd0bc7..59caae8f1bc 100644
--- a/src/backend/catalog/catalog.c
+++ b/src/backend/catalog/catalog.c
@@ -346,8 +346,6 @@ IsSharedRelation(Oid relationId)
 		relationId == PgDbRoleSettingToastIndex ||
 		relationId == PgParameterAclToastTable ||
 		relationId == PgParameterAclToastIndex ||
-		relationId == PgReplicationOriginToastTable ||
-		relationId == PgReplicationOriginToastIndex ||
 		relationId == PgShdescriptionToastTable ||
 		relationId == PgShdescriptionToastIndex ||
 		relationId == PgShseclabelToastTable ||
diff --git a/src/backend/replication/logical/origin.c b/src/backend/replication/logical/origin.c
index 6583dd497da..bd827bc6ed0 100644
--- a/src/backend/replication/logical/origin.c
+++ b/src/backend/replication/logical/origin.c
@@ -287,6 +287,16 @@ replorigin_create(const char *roname)
 
 	rel = table_open(ReplicationOriginRelationId, ExclusiveLock);
 
+	/*
+	 * We want to be able to access pg_replication_origin without setting up a
+	 * snapshot. As of this writing, its TOAST table would only be used for
+	 * replication origin names, which we avoid with a reasonable length
+	 * restriction.  If you add a TOAST table to this catalog, be sure to set
+	 * up a snapshot everywhere it might be needed.  For more information, see
+	 * https://postgr.es/m/ZvMSUPOqUU-VNADN%40nathan.
+	 */
+	Assert(!OidIsValid(rel->rd_rel->reltoastrelid));
+
 	for (roident = InvalidOid + 1; roident < PG_UINT16_MAX; roident++)
 	{
 		bool		nulls[Natts_pg_replication_origin];
@@ -1296,6 +1306,18 @@ pg_replication_origin_create(PG_FUNCTION_ARGS)
 		elog(WARNING, "replication origins created by regression test cases should have names starting with \"regress_\"");
 #endif
 
+	/*
+	 * To avoid needing a TOAST table for pg_replication_origin, we restrict
+	 * replication origin names to 512 bytes.  This should be more than enough
+	 * for all practical use.
+	 */
+	if (strlen(name) > MAX_RONAME_LEN)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
+				 errmsg("replication origin name is too long"),
+				 errdetail("Replication origin names must be no longer than %d bytes.",
+						   MAX_RONAME_LEN)));
+
 	roident = replorigin_create(name);
 
 	pfree(name);
diff --git a/src/include/catalog/pg_replication_origin.h b/src/include/catalog/pg_replication_origin.h
index deb43065fe9..7ade8bbda39 100644
--- a/src/include/catalog/pg_replication_origin.h
+++ b/src/include/catalog/pg_replication_origin.h
@@ -54,8 +54,6 @@ CATALOG(pg_replication_origin,6000,ReplicationOriginRelationId) BKI_SHARED_RELAT
 
 typedef FormData_pg_replication_origin *Form_pg_replication_origin;
 
-DECLARE_TOAST_WITH_MACRO(pg_replication_origin, 4181, 4182, PgReplicationOriginToastTable, PgReplicationOriginToastIndex);
-
 DECLARE_UNIQUE_INDEX_PKEY(pg_replication_origin_roiident_index, 6001, ReplicationOriginIdentIndex, pg_replication_origin, btree(roident oid_ops));
 DECLARE_UNIQUE_INDEX(pg_replication_origin_roname_index, 6002, ReplicationOriginNameIndex, pg_replication_origin, btree(roname text_ops));
 
diff --git a/src/include/replication/origin.h b/src/include/replication/origin.h
index 9cb2248fa9f..29724c0dcae 100644
--- a/src/include/replication/origin.h
+++ b/src/include/replication/origin.h
@@ -33,6 +33,13 @@ typedef struct xl_replorigin_drop
 #define InvalidRepOriginId 0
 #define DoNotReplicateId PG_UINT16_MAX
 
+/*
+ * To avoid needing a TOAST table for pg_replication_origin, we restrict
+ * replication origin names to 512 bytes.  This should be more than enough for
+ * all practical use.
+ */
+#define MAX_RONAME_LEN	512
+
 extern PGDLLIMPORT RepOriginId replorigin_session_origin;
 extern PGDLLIMPORT XLogRecPtr replorigin_session_origin_lsn;
 extern PGDLLIMPORT TimestampTz replorigin_session_origin_timestamp;
diff --git a/src/test/regress/expected/misc_functions.out b/src/test/regress/expected/misc_functions.out
index d3f5d16a672..3de32c3c7ef 100644
--- a/src/test/regress/expected/misc_functions.out
+++ b/src/test/regress/expected/misc_functions.out
@@ -914,3 +914,7 @@ SELECT test_relpath();
  
 (1 row)
 
+-- pg_replication_origin.roname length restriction
+SELECT pg_replication_origin_create('regress_' || repeat('a', 505));
+ERROR:  replication origin name is too long
+DETAIL:  Replication origin names must be no longer than 512 bytes.
diff --git a/src/test/regress/expected/misc_sanity.out b/src/test/regress/expected/misc_sanity.out
index b032a3f4761..b0b76fe3d9a 100644
--- a/src/test/regress/expected/misc_sanity.out
+++ b/src/test/regress/expected/misc_sanity.out
@@ -42,6 +42,10 @@ WHERE refclassid = 0 OR refobjid = 0 OR
 -- as user data by pg_upgrade, which would cause failures.
 -- 3. pg_authid, since its toast table cannot be accessed when it would be
 -- needed, i.e., during authentication before we've selected a database.
+-- 4. pg_replication_origin, since we want to be able to access that catalog
+-- without setting up a snapshot.  As of this writing, its toast table would
+-- only be used for replication origin names, which we can avoid with a
+-- reasonable length restriction.
 SELECT relname, attname, atttypid::regtype
 FROM pg_class c JOIN pg_attribute a ON c.oid = attrelid
 WHERE c.oid < 16384 AND
@@ -61,7 +65,8 @@ ORDER BY 1, 2;
  pg_class                | relpartbound  | pg_node_tree
  pg_largeobject          | data          | bytea
  pg_largeobject_metadata | lomacl        | aclitem[]
-(10 rows)
+ pg_replication_origin   | roname        | text
+(11 rows)
 
 -- system catalogs without primary keys
 --
diff --git a/src/test/regress/sql/misc_functions.sql b/src/test/regress/sql/misc_functions.sql
index aaebb298330..ea72a62dab7 100644
--- a/src/test/regress/sql/misc_functions.sql
+++ b/src/test/regress/sql/misc_functions.sql
@@ -411,3 +411,6 @@ CREATE FUNCTION test_relpath()
     AS :'regresslib'
     LANGUAGE C;
 SELECT test_relpath();
+
+-- pg_replication_origin.roname length restriction
+SELECT pg_replication_origin_create('regress_' || repeat('a', 505));
diff --git a/src/test/regress/sql/misc_sanity.sql b/src/test/regress/sql/misc_sanity.sql
index 135793871b4..86c193a0c42 100644
--- a/src/test/regress/sql/misc_sanity.sql
+++ b/src/test/regress/sql/misc_sanity.sql
@@ -45,6 +45,10 @@ WHERE refclassid = 0 OR refobjid = 0 OR
 -- as user data by pg_upgrade, which would cause failures.
 -- 3. pg_authid, since its toast table cannot be accessed when it would be
 -- needed, i.e., during authentication before we've selected a database.
+-- 4. pg_replication_origin, since we want to be able to access that catalog
+-- without setting up a snapshot.  As of this writing, its toast table would
+-- only be used for replication origin names, which we can avoid with a
+-- reasonable length restriction.
 
 SELECT relname, attname, atttypid::regtype
 FROM pg_class c JOIN pg_attribute a ON c.oid = attrelid
-- 
2.39.5 (Apple Git-154)


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