Do not explicitly create NOT NULL constraints for columns in PRIMARY KEY.

NOT NULL constraint is created automatically for each column in the PRIMARY
KEY. So far it was fine to create the NOT NULL constraint explicitly - the
attempt was silently ignored. However, it causes ERROR in PostgreSQL >= 18.2.

Bumped version number to 2.1.

Author: Antonin Houska

Makefile

@@ -5,7 +5,7 @@ PGFILEDESC = "pg_rewrite - tools for maintenance that requires table rewriting."
 
 EXTENSION = pg_rewrite
 DATA = pg_rewrite--1.0.sql pg_rewrite--1.0--1.1.sql pg_rewrite--1.1--1.2.sql\
-pg_rewrite--1.2--2.0.sql pg_rewrite--1.3--2.0.sql
+pg_rewrite--1.2--2.0.sql pg_rewrite--1.3--2.0.sql pg_rewrite--2.0--2.1.sql
 DOCS = pg_rewrite.md
 
 REGRESS = pg_rewrite generated

NEWS

@@ -1,3 +1,17 @@
+Release 2.1
+===========
+
+1. Do not try to create NOT NULL constraint unnecessarily.
+
+NOT NULL constraint is automatically created for columns involved in PRIMARY
+KEY constraint. Thus if the old table has a NOT NULL constraint in the
+catalog, we should only create it on the new table if the related column is
+not part of primary key.
+
+While this unnecessary ALTER TABLE ... ADD CONSTRAINT ... NOT NULL command
+used to be ignored silently so far, it causes ERROR since PostgreSQL 18.2.
+
+
 Release 2.0
 ===========
 

README.md

@@ -154,7 +154,7 @@ source table. It's recommended to handle constraints creation this way:
     constraints of the source table to the target table. `rewrite_table()`
     by-passes validation of these, but all the rows it inserts into the target
     table must have been validated in the source table. Even if the column
-    data tape is different in the target table, the data type conversion
+    data type is different in the target table, the data type conversion
     should not turn non-NULL value to NULL or vice versa.
 
 3.  CHECK constraints are created automatically by `rewrite_table()`

pg_rewrite--2.0--2.1.sql

@@ -0,0 +1 @@
+-- No SQL changes for this upgrade.

pg_rewrite.c

@@ -77,7 +77,7 @@
 #include "utils/varlena.h"
 
 #ifdef PG_MODULE_MAGIC_EXT
-PG_MODULE_MAGIC_EXT(.name = "pg_rewrite", .version = "2.0");
+PG_MODULE_MAGIC_EXT(.name = "pg_rewrite", .version = "2.1");
 #else
 PG_MODULE_MAGIC;
 #endif
@@ -179,6 +179,7 @@ static void dump_check_constraint(Oid relid_dst, const char *relname_dst,
 #if PG_VERSION_NUM >= 180000
 static void dump_null_constraint(Oid relid_dst, const char *relname_dst,
 								 HeapTuple tup, StringInfo buf);
+static bool is_notnull_in_pk(Form_pg_constraint notnull, Oid relid);
 #endif
 static void dump_constraint_common(const char *nsp, const char *relname,
 								   Form_pg_constraint con, StringInfo buf);
@@ -3327,7 +3328,12 @@ copy_constraints(Oid relid_dst, const char *relname_dst, Oid relid_src)
 #if PG_VERSION_NUM >= 180000
 			case CONSTRAINT_NOTNULL:
 				{
-					if (con->conrelid == relid_src)
+					/*
+					 * Do not create NOT NULL constraint if it should already
+					 * exist due to primary key constraint.
+					 */
+					if (con->conrelid == relid_src &&
+						!is_notnull_in_pk(con, relid_src))
 						dump_null_constraint(relid_dst, relname_dst, tuple,
 											 buf);
 					break;
@@ -3655,6 +3661,25 @@ dump_null_constraint(Oid relid_dst, const char *relname_dst,
 		appendStringInfoString(buf, " NO INHERIT");
 
 }
+
+/*
+ * Should NOT NULL constraint have already been created due to PK of table
+ * specified by 'relid'?
+ */
+static bool
+is_notnull_in_pk(Form_pg_constraint notnull, Oid relid)
+{
+	Bitmapset	*notnull_attnos, *pk_attnos;
+	Oid		notnullid, pkoid;
+
+	notnull_attnos = get_relation_constraint_attnos(relid,
+													NameStr(notnull->conname),
+													false, &notnullid);
+	Assert(bms_num_members(notnull_attnos) == 1);
+	pk_attnos = get_primary_key_attnos(relid, true, &pkoid);
+
+	return bms_overlap(notnull_attnos, pk_attnos);
+}
 #endif
 
 static void

pg_rewrite.control

@@ -1,5 +1,5 @@
 # pg_rewrite extension
 comment = 'Tool for maintenance that requires table rewriting.'
-default_version = '2.0'
+default_version = '2.1'
 module_pathname = '$libdir/pg_rewrite'
 relocatable = true