From fe4043aea631bf38bc7502aac4225c74f44a73a3 Mon Sep 17 00:00:00 2001
From: Ronan Dunklau <ronan.dunklau@aiven.io>
Date: Fri, 1 Mar 2024 09:45:48 +0100
Subject: [PATCH 1/2] Provide an aiven_extras.truncate_freespacemap function

When a bug involving FSM corruption, we currently have no easy way of fixing it.
We can either VACUUM FULL the relation, which will rewrite everything including the FSM. Or we can stop the service, delete the FSM manually, and restart it.

This function is copy-pasted from pg_truncate_visibility_map, and allows to truncate an FSM online.
---
 Makefile                                |  2 +-
 sql/aiven_extras.sql                    |  6 +++
 src/{standby_slots.c => aiven_extras.c} | 69 +++++++++++++++++++++++++
 3 files changed, 76 insertions(+), 1 deletion(-)
 rename src/{standby_slots.c => aiven_extras.c} (69%)

diff --git a/Makefile b/Makefile
index 77a28c0..a9b5860 100644
--- a/Makefile
+++ b/Makefile
@@ -11,7 +11,7 @@ RPM_MINOR_VERSION_SUFFIX ?=
 # Extension packaging
 EXTENSION = aiven_extras
 MODULE_big = aiven_extras
-OBJS = src/standby_slots.o
+OBJS = src/aiven_extras.o
 PG_CONFIG ?= pg_config
 DATA = $(filter-out $(generated),$(wildcard sql/*--*.sql))
 DATA_built = $(generated)
diff --git a/sql/aiven_extras.sql b/sql/aiven_extras.sql
index f346b87..e4449f4 100644
--- a/sql/aiven_extras.sql
+++ b/sql/aiven_extras.sql
@@ -580,3 +580,9 @@ CREATE FUNCTION aiven_extras.pg_create_logical_replication_slot_on_standby(
 	OUT slot_name name, OUT lsn pg_lsn)
 AS 'MODULE_PATHNAME', 'standby_slot_create'
 LANGUAGE C;
+
+DROP FUNCTION IF EXISTS aiven_extras.aiven_truncate_freespace_map(regclass);
+CREATE FUNCTION aiven_extras.truncate_freespace_map(regclass)
+RETURNS void 
+AS 'MODULE_PATHNAME', 'aiven_truncate_freespace_map'
+LANGUAGE C;
diff --git a/src/standby_slots.c b/src/aiven_extras.c
similarity index 69%
rename from src/standby_slots.c
rename to src/aiven_extras.c
index f056948..630ec53 100644
--- a/src/standby_slots.c
+++ b/src/aiven_extras.c
@@ -2,19 +2,28 @@
 #include "fmgr.h"
 #include "funcapi.h"
 #include "miscadmin.h"
+#include "storage/freespace.h"
+#include "storage/smgr.h"
+#if PG_VERSION_NUM >= 160000
+#include "access/relation.h"
+#endif
+#include "access/xloginsert.h"
 #include "access/xlogreader.h"
 #include "access/xlogutils.h"
 #include "replication/logical.h"
+#include "catalog/storage_xlog.h"
 #include "replication/slot.h"
 #include "replication/walreceiver.h"
 #if PG_VERSION_NUM >= 120000 && PG_VERSION_NUM < 130000
 #include "replication/logicalfuncs.h"
 #endif
 #include "utils/pg_lsn.h"
+#include "utils/rel.h"
 
 PG_MODULE_MAGIC;
 
 PG_FUNCTION_INFO_V1(standby_slot_create);
+PG_FUNCTION_INFO_V1(aiven_truncate_freespace_map);
 	Datum
 standby_slot_create(PG_FUNCTION_ARGS)
 {
@@ -120,3 +129,63 @@ standby_slot_create(PG_FUNCTION_ARGS)
 	ReplicationSlotRelease();
 	PG_RETURN_DATUM(result);
 }
+
+
+
+#if PG_VERSION_NUM >= 160000
+Datum
+aiven_truncate_freespace_map(PG_FUNCTION_ARGS)
+{
+	Oid			relid = PG_GETARG_OID(0);
+	Relation	rel;
+	ForkNumber	fork;
+	BlockNumber block;
+
+	rel = relation_open(relid, AccessExclusiveLock);
+
+	/* Only some relkinds have a freespacemap map */
+	if (!RELKIND_HAS_TABLE_AM(rel->rd_rel->relkind))
+		ereport(ERROR,
+				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				 errmsg("relation \"%s\" is of wrong relation kind",
+						RelationGetRelationName(rel)),
+				 errdetail_relkind_not_supported(rel->rd_rel->relkind)));
+
+
+	/* Forcibly reset cached file size */
+	RelationGetSmgr(rel)->smgr_cached_nblocks[FSM_FORKNUM] = InvalidBlockNumber;
+
+	/* Just pretend we're going to wipeout the whole rel */
+	block = FreeSpaceMapPrepareTruncateRel(rel, 0);
+
+	if (BlockNumberIsValid(block))
+	{
+		fork = FSM_FORKNUM;
+		smgrtruncate(RelationGetSmgr(rel), &fork, 1, &block);
+	}
+
+	if (RelationNeedsWAL(rel))
+	{
+		xl_smgr_truncate xlrec;
+
+		xlrec.blkno = 0;
+		xlrec.rlocator = rel->rd_locator;
+		xlrec.flags = SMGR_TRUNCATE_FSM;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, sizeof(xlrec));
+
+		XLogInsert(RM_SMGR_ID, XLOG_SMGR_TRUNCATE | XLR_SPECIAL_REL_UPDATE);
+	}
+
+	relation_close(rel, AccessExclusiveLock);
+
+	PG_RETURN_VOID();
+}
+#else
+Datum
+aiven_truncate_freespace_map(PG_FUNCTION_ARGS)
+{
+	elog(ERROR, "aiven_truncate_freespace_map is not supported on this version.");
+}
+#endif

From 72ca8614b508a388e9ba0a660b7c9fa1eb65a5c8 Mon Sep 17 00:00:00 2001
From: Ronan Dunklau <ronan.dunklau@aiven.io>
Date: Fri, 1 Mar 2024 09:50:17 +0100
Subject: [PATCH 2/2] Bump version

---
 Makefile                             | 4 ++--
 sql/aiven_extras--1.1.10--1.1.11.sql | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)
 create mode 100644 sql/aiven_extras--1.1.10--1.1.11.sql

diff --git a/Makefile b/Makefile
index a9b5860..84ffa85 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
-short_ver = 1.1.11
-last_ver = 1.1.10
+short_ver = 1.1.12
+last_ver = 1.1.11
 long_ver = $(shell git describe --long 2>/dev/null || echo $(short_ver)-0-unknown-g`git describe --always`)
 generated = aiven_extras.control \
 			sql/aiven_extras--$(short_ver).sql \
diff --git a/sql/aiven_extras--1.1.10--1.1.11.sql b/sql/aiven_extras--1.1.10--1.1.11.sql
new file mode 100644
index 0000000..e2f08fc
--- /dev/null
+++ b/sql/aiven_extras--1.1.10--1.1.11.sql
@@ -0,0 +1 @@
+-- NOOP