From 344d62fb9a978a72cf8347f0369b9ee643fd0b31 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Thu, 7 Apr 2022 16:13:23 +0200
Subject: Unlogged sequences

Add support for unlogged sequences.  Unlike for unlogged tables, this
is not a performance feature.  It allows sequences associated with
unlogged tables to be excluded from replication.

A new subcommand ALTER SEQUENCE ... SET LOGGED/UNLOGGED is added.

An identity/serial sequence now automatically gets and follows the
persistence level (logged/unlogged) of its owning table.  (The
sequences owned by temporary tables were already temporary through the
separate mechanism in RangeVarAdjustRelationPersistence().)  But you
can still change the persistence of an owned sequence separately.
Also, pg_dump and pg_upgrade preserve the persistence of existing
sequences.

Discussion: https://www.postgresql.org/message-id/flat/04e12818-2f98-257c-b926-2845d74ed04f%402ndquadrant.com
---
 src/backend/commands/tablecmds.c | 32 +++++++++++++++++++++++++++++---
 1 file changed, 29 insertions(+), 3 deletions(-)

(limited to 'src/backend/commands/tablecmds.c')

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index a241b444975..4dd545cdd20 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -319,6 +319,7 @@ struct DropRelationCallbackState
 #define		ATT_COMPOSITE_TYPE		0x0010
 #define		ATT_FOREIGN_TABLE		0x0020
 #define		ATT_PARTITIONED_INDEX	0x0040
+#define		ATT_SEQUENCE			0x0080
 
 /*
  * ForeignTruncateInfo
@@ -4660,7 +4661,7 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			pass = AT_PASS_MISC;
 			break;
 		case AT_SetLogged:		/* SET LOGGED */
-			ATSimplePermissions(cmd->subtype, rel, ATT_TABLE);
+			ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_SEQUENCE);
 			if (tab->chgPersistence)
 				ereport(ERROR,
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -4675,7 +4676,7 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			pass = AT_PASS_MISC;
 			break;
 		case AT_SetUnLogged:	/* SET UNLOGGED */
-			ATSimplePermissions(cmd->subtype, rel, ATT_TABLE);
+			ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_SEQUENCE);
 			if (tab->chgPersistence)
 				ereport(ERROR,
 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -5425,7 +5426,7 @@ ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode,
 		 * and assigns a new relfilenode, we automatically create or drop an
 		 * init fork for the relation as appropriate.
 		 */
-		if (tab->rewrite > 0)
+		if (tab->rewrite > 0 && tab->relkind != RELKIND_SEQUENCE)
 		{
 			/* Build a temporary relation and copy data */
 			Relation	OldHeap;
@@ -5546,6 +5547,11 @@ ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode,
 
 			InvokeObjectPostAlterHook(RelationRelationId, tab->relid, 0);
 		}
+		else if (tab->rewrite > 0 && tab->relkind == RELKIND_SEQUENCE)
+		{
+			if (tab->chgPersistence)
+				SequenceChangePersistence(tab->relid, tab->newrelpersistence);
+		}
 		else
 		{
 			/*
@@ -5564,6 +5570,23 @@ ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode,
 			if (tab->newTableSpace)
 				ATExecSetTableSpace(tab->relid, tab->newTableSpace, lockmode);
 		}
+
+		/*
+		 * Also change persistence of owned sequences, so that it matches the
+		 * table persistence.
+		 */
+		if (tab->chgPersistence)
+		{
+			List	   *seqlist = getOwnedSequences(tab->relid);
+			ListCell   *lc;
+
+			foreach(lc, seqlist)
+			{
+				Oid         seq_relid = lfirst_oid(lc);
+
+				SequenceChangePersistence(seq_relid, tab->newrelpersistence);
+			}
+		}
 	}
 
 	/*
@@ -6224,6 +6247,9 @@ ATSimplePermissions(AlterTableType cmdtype, Relation rel, int allowed_targets)
 		case RELKIND_FOREIGN_TABLE:
 			actual_target = ATT_FOREIGN_TABLE;
 			break;
+		case RELKIND_SEQUENCE:
+			actual_target = ATT_SEQUENCE;
+			break;
 		default:
 			actual_target = 0;
 			break;
-- 
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