Fix propagation of persistence to sequences in ALTER TABLE / ADD COLUMN

Fix for 344d62fb9a9: That commit introduced unlogged sequences and
made it so that identity/serial sequences automatically get the
persistence level of their owning table.  But this works only for
CREATE TABLE and not for ALTER TABLE / ADD COLUMN.  The latter would
always create the sequence as logged (default), independent of the
persistence setting of the table.  This is fixed here.

Note: It is allowed to change the persistence of identity sequences
directly using ALTER SEQUENCE.  So mistakes in existing databases can
be fixed manually.

Reviewed-by: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/c4b6e2ed-bcdf-4ea7-965f-e49761094827%40eisentraut.org

1 files changed, 10 insertions, 1 deletions

diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index d67580fc77a..9dcfc718275 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -456,7 +456,16 @@ generateSerialExtraStmts(CreateStmtContext *cxt, ColumnDef *column,
 	seqstmt = makeNode(CreateSeqStmt);
 	seqstmt->for_identity = for_identity;
 	seqstmt->sequence = makeRangeVar(snamespace, sname, -1);
-	seqstmt->sequence->relpersistence = cxt->relation->relpersistence;
+
+	/*
+	 * Copy the persistence of the table.  For CREATE TABLE, we get the
+	 * persistence from cxt->relation, which comes from the CreateStmt in
+	 * progress.  For ALTER TABLE, the parser won't set
+	 * cxt->relation->relpersistence, but we have cxt->rel as the existing
+	 * table, so we copy the persistence from there.
+	 */
+	seqstmt->sequence->relpersistence = cxt->rel ? cxt->rel->rd_rel->relpersistence : cxt->relation->relpersistence;
+
 	seqstmt->options = seqoptions;
 
 	/*