pg_dump: include comments on valid not-null constraints, too

We were missing collecting comments for not-null constraints that are
dumped inline with the table definition (i.e., valid ones), because they
aren't represented by a separately dumpable object.  Fix by creating
separate TocEntries for the comments.

Co-Authored-By: Jian He <jian.universality@gmail.com>
Co-Authored-By: Álvaro Herrera <alvherre@kurilemu.de>
Reported-By: Fujii Masao <masao.fujii@oss.nttdata.com>
Reviewed-By: Fujii Masao <masao.fujii@oss.nttdata.com>
Discussion: https://postgr.es/m/d50ff977-c728-4e9e-8488-fc2688e08754@oss.nttdata.com

doc/src/sgml/ref/pg_dump.sgml

@@ -1281,7 +1281,7 @@ PostgreSQL documentation
           materialized views, and foriegn tables.
           Post-data items include definitions of indexes, triggers, rules,
           statistics for indexes, and constraints other than validated check
-          constraints.
+          and not-null constraints.
           Pre-data items include all other data definition items.
          </para>
        </listitem>

src/bin/pg_dump/pg_dump.c

@@ -350,7 +350,9 @@ static void buildMatViewRefreshDependencies(Archive *fout);
 static void getTableDataFKConstraints(void);
 static void determineNotNullFlags(Archive *fout, PGresult *res, int r,
 								  TableInfo *tbinfo, int j,
-								  int i_notnull_name, int i_notnull_invalidoid,
+								  int i_notnull_name,
+								  int i_notnull_comment,
+								  int i_notnull_invalidoid,
 								  int i_notnull_noinherit,
 								  int i_notnull_islocal,
 								  PQExpBuffer *invalidnotnulloids);
@@ -9006,6 +9008,7 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 	int			i_attalign;
 	int			i_attislocal;
 	int			i_notnull_name;
+	int			i_notnull_comment;
 	int			i_notnull_noinherit;
 	int			i_notnull_islocal;
 	int			i_notnull_invalidoid;
@@ -9089,7 +9092,8 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 
 	/*
 	 * Find out any NOT NULL markings for each column.  In 18 and up we read
-	 * pg_constraint to obtain the constraint name.  notnull_noinherit is set
+	 * pg_constraint to obtain the constraint name, and for valid constraints
+	 * also pg_description to obtain its comment.  notnull_noinherit is set
 	 * according to the NO INHERIT property.  For versions prior to 18, we
 	 * store an empty string as the name when a constraint is marked as
 	 * attnotnull (this cues dumpTableSchema to print the NOT NULL clause
@@ -9097,7 +9101,8 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 	 *
 	 * For invalid constraints, we need to store their OIDs for processing
 	 * elsewhere, so we bring the pg_constraint.oid value when the constraint
-	 * is invalid, and NULL otherwise.
+	 * is invalid, and NULL otherwise.  Their comments are handled not here
+	 * but by collectComments, because they're their own dumpable object.
 	 *
 	 * We track in notnull_islocal whether the constraint was defined directly
 	 * in this table or via an ancestor, for binary upgrade.  flagInhAttrs
@@ -9107,6 +9112,8 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 	if (fout->remoteVersion >= 180000)
 		appendPQExpBufferStr(q,
 							 "co.conname AS notnull_name,\n"
+							 "CASE WHEN co.convalidated THEN pt.description"
+							 " ELSE NULL END AS notnull_comment,\n"
 							 "CASE WHEN NOT co.convalidated THEN co.oid "
 							 "ELSE NULL END AS notnull_invalidoid,\n"
 							 "co.connoinherit AS notnull_noinherit,\n"
@@ -9114,6 +9121,7 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 	else
 		appendPQExpBufferStr(q,
 							 "CASE WHEN a.attnotnull THEN '' ELSE NULL END AS notnull_name,\n"
+							 "NULL AS notnull_comment,\n"
 							 "NULL AS notnull_invalidoid,\n"
 							 "false AS notnull_noinherit,\n"
 							 "a.attislocal AS notnull_islocal,\n");
@@ -9157,15 +9165,16 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 
 	/*
 	 * In versions 18 and up, we need pg_constraint for explicit NOT NULL
-	 * entries.  Also, we need to know if the NOT NULL for each column is
-	 * backing a primary key.
+	 * entries and pg_description to get their comments.
 	 */
 	if (fout->remoteVersion >= 180000)
 		appendPQExpBufferStr(q,
 							 " LEFT JOIN pg_catalog.pg_constraint co ON "
 							 "(a.attrelid = co.conrelid\n"
 							 "   AND co.contype = 'n' AND "
-							 "co.conkey = array[a.attnum])\n");
+							 "co.conkey = array[a.attnum])\n"
+							 " LEFT JOIN pg_catalog.pg_description pt ON "
+							 "(pt.classoid = co.tableoid AND pt.objoid = co.oid)\n");
 
 	appendPQExpBufferStr(q,
 						 "WHERE a.attnum > 0::pg_catalog.int2\n"
@@ -9189,6 +9198,7 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 	i_attalign = PQfnumber(res, "attalign");
 	i_attislocal = PQfnumber(res, "attislocal");
 	i_notnull_name = PQfnumber(res, "notnull_name");
+	i_notnull_comment = PQfnumber(res, "notnull_comment");
 	i_notnull_invalidoid = PQfnumber(res, "notnull_invalidoid");
 	i_notnull_noinherit = PQfnumber(res, "notnull_noinherit");
 	i_notnull_islocal = PQfnumber(res, "notnull_islocal");
@@ -9257,6 +9267,7 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 		tbinfo->attfdwoptions = (char **) pg_malloc(numatts * sizeof(char *));
 		tbinfo->attmissingval = (char **) pg_malloc(numatts * sizeof(char *));
 		tbinfo->notnull_constrs = (char **) pg_malloc(numatts * sizeof(char *));
+		tbinfo->notnull_comment = (char **) pg_malloc(numatts * sizeof(char *));
 		tbinfo->notnull_invalid = (bool *) pg_malloc(numatts * sizeof(bool));
 		tbinfo->notnull_noinh = (bool *) pg_malloc(numatts * sizeof(bool));
 		tbinfo->notnull_islocal = (bool *) pg_malloc(numatts * sizeof(bool));
@@ -9288,11 +9299,14 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
 			determineNotNullFlags(fout, res, r,
 								  tbinfo, j,
 								  i_notnull_name,
+								  i_notnull_comment,
 								  i_notnull_invalidoid,
 								  i_notnull_noinherit,
 								  i_notnull_islocal,
 								  &invalidnotnulloids);
 
+			tbinfo->notnull_comment[j] = PQgetisnull(res, r, i_notnull_comment) ?
+				NULL : pg_strdup(PQgetvalue(res, r, i_notnull_comment));
 			tbinfo->attoptions[j] = pg_strdup(PQgetvalue(res, r, i_attoptions));
 			tbinfo->attcollation[j] = atooid(PQgetvalue(res, r, i_attcollation));
 			tbinfo->attcompression[j] = *(PQgetvalue(res, r, i_attcompression));
@@ -9704,8 +9718,9 @@ getTableAttrs(Archive *fout, TableInfo *tblinfo, int numTables)
  * 4) The column has a constraint with a known name; in that case
  *    notnull_constrs carries that name and dumpTableSchema will print
  *    "CONSTRAINT the_name NOT NULL".  However, if the name is the default
- *    (table_column_not_null), there's no need to print that name in the dump,
- *    so notnull_constrs is set to the empty string and it behaves as case 2.
+ *    (table_column_not_null) and there's no comment on the constraint,
+ *    there's no need to print that name in the dump, so notnull_constrs
+ *    is set to the empty string and it behaves as case 2.
  *
  * In a child table that inherits from a parent already containing NOT NULL
  * constraints and the columns in the child don't have their own NOT NULL
@@ -9732,6 +9747,7 @@ static void
 determineNotNullFlags(Archive *fout, PGresult *res, int r,
 					  TableInfo *tbinfo, int j,
 					  int i_notnull_name,
+					  int i_notnull_comment,
 					  int i_notnull_invalidoid,
 					  int i_notnull_noinherit,
 					  int i_notnull_islocal,
@@ -9805,11 +9821,13 @@ determineNotNullFlags(Archive *fout, PGresult *res, int r,
 		{
 			/*
 			 * In binary upgrade of inheritance child tables, must have a
-			 * constraint name that we can UPDATE later.
+			 * constraint name that we can UPDATE later; same if there's a
+			 * comment on the constraint.
 			 */
-			if (dopt->binary_upgrade &&
+			if ((dopt->binary_upgrade &&
 				 !tbinfo->ispartition &&
-				!tbinfo->notnull_islocal)
+				 !tbinfo->notnull_islocal) ||
+				!PQgetisnull(res, r, i_notnull_comment))
 			{
 				tbinfo->notnull_constrs[j] =
 					pstrdup(PQgetvalue(res, r, i_notnull_name));
@@ -17686,6 +17704,56 @@ dumpTableSchema(Archive *fout, const TableInfo *tbinfo)
 	if (tbinfo->dobj.dump & DUMP_COMPONENT_SECLABEL)
 		dumpTableSecLabel(fout, tbinfo, reltypename);
 
+	/*
+	 * Dump comments for not-null constraints that aren't to be dumped
+	 * separately (those are processed by collectComments/dumpComment).
+	 */
+	if (!fout->dopt->no_comments && dopt->dumpSchema &&
+		fout->remoteVersion >= 180000)
+	{
+		PQExpBuffer comment = NULL;
+		PQExpBuffer tag = NULL;
+
+		for (j = 0; j < tbinfo->numatts; j++)
+		{
+			if (tbinfo->notnull_constrs[j] != NULL &&
+				tbinfo->notnull_comment[j] != NULL)
+			{
+				if (comment == NULL)
+				{
+					comment = createPQExpBuffer();
+					tag = createPQExpBuffer();
+				}
+				else
+				{
+					resetPQExpBuffer(comment);
+					resetPQExpBuffer(tag);
+				}
+
+				appendPQExpBuffer(comment, "COMMENT ON CONSTRAINT %s ON %s IS ",
+								  fmtId(tbinfo->notnull_constrs[j]), qualrelname);
+				appendStringLiteralAH(comment, tbinfo->notnull_comment[j], fout);
+				appendPQExpBufferStr(comment, ";\n");
+
+				appendPQExpBuffer(tag, "CONSTRAINT %s ON %s",
+								  fmtId(tbinfo->notnull_constrs[j]), qrelname);
+
+				ArchiveEntry(fout, nilCatalogId, createDumpId(),
+							 ARCHIVE_OPTS(.tag = tag->data,
+										  .namespace = tbinfo->dobj.namespace->dobj.name,
+										  .owner = tbinfo->rolname,
+										  .description = "COMMENT",
+										  .section = SECTION_NONE,
+										  .createStmt = comment->data,
+										  .deps = &(tbinfo->dobj.dumpId),
+										  .nDeps = 1));
+			}
+		}
+
+		destroyPQExpBuffer(comment);
+		destroyPQExpBuffer(tag);
+	}
+
 	/* Dump comments on inlined table constraints */
 	for (j = 0; j < tbinfo->ncheck; j++)
 	{

src/bin/pg_dump/pg_dump.h

@@ -365,6 +365,7 @@ typedef struct _tableInfo
 									 * there isn't one on this column. If
 									 * empty string, unnamed constraint
 									 * (pre-v17) */
+	char	  **notnull_comment;	/* comment thereof */
 	bool	   *notnull_invalid;	/* true for NOT NULL NOT VALID */
 	bool	   *notnull_noinh;	/* NOT NULL is NO INHERIT */
 	bool	   *notnull_islocal;	/* true if NOT NULL has local definition */

src/bin/pg_dump/t/002_pg_dump.pl

@@ -1191,7 +1191,9 @@ my %tests = (
 							) INHERITS (dump_test.test_table_nn, dump_test.test_table_nn_2);
 			ALTER TABLE dump_test.test_table_nn ADD CONSTRAINT nn NOT NULL col1 NOT VALID;
 			ALTER TABLE dump_test.test_table_nn_chld1 VALIDATE CONSTRAINT nn;
-			ALTER TABLE dump_test.test_table_nn_chld2 VALIDATE CONSTRAINT nn;',
+			ALTER TABLE dump_test.test_table_nn_chld2 VALIDATE CONSTRAINT nn;
+			COMMENT ON CONSTRAINT nn ON dump_test.test_table_nn IS \'nn comment is valid\';
+			COMMENT ON CONSTRAINT nn ON dump_test.test_table_nn_chld2 IS \'nn_chld2 comment is valid\';',
 		regexp => qr/^
 			\QALTER TABLE dump_test.test_table_nn\E \n^\s+
 			\QADD CONSTRAINT nn NOT NULL col1 NOT VALID;\E
@@ -1205,6 +1207,34 @@ my %tests = (
 		},
 	},
 
+	# This constraint is invalid therefore it goes in SECTION_POST_DATA
+	'COMMENT ON CONSTRAINT ON test_table_nn' => {
+		regexp => qr/^
+		\QCOMMENT ON CONSTRAINT nn ON dump_test.test_table_nn IS\E
+		/xm,
+		like => {
+			%full_runs, %dump_test_schema_runs, section_post_data => 1,
+		},
+		unlike => {
+			exclude_dump_test_schema => 1,
+			only_dump_measurement => 1,
+		},
+	},
+
+	# This constraint is valid therefore it goes in SECTION_PRE_DATA
+	'COMMENT ON CONSTRAINT ON test_table_chld2' => {
+		regexp => qr/^
+		\QCOMMENT ON CONSTRAINT nn ON dump_test.test_table_nn_chld2 IS\E
+		/xm,
+		like => {
+			%full_runs, %dump_test_schema_runs, section_pre_data => 1,
+		},
+		unlike => {
+			exclude_dump_test_schema => 1,
+			only_dump_measurement => 1,
+		},
+	},
+
 	'CONSTRAINT NOT NULL / NOT VALID (child1)' => {
 		regexp => qr/^
 		\QCREATE TABLE dump_test.test_table_nn_chld1 (\E\n

src/test/regress/expected/constraints.out

@@ -1659,6 +1659,8 @@ EXECUTE get_nnconstraint_info('{constr_parent3, constr_child3}');
  constr_parent3 | constr_parent3_a_not_null | t            | t          |           0
 (2 rows)
 
+COMMENT ON CONSTRAINT constr_parent2_a_not_null ON constr_parent2 IS 'this constraint is invalid';
+COMMENT ON CONSTRAINT constr_parent2_a_not_null ON constr_child2 IS 'this constraint is valid';
 DEALLOCATE get_nnconstraint_info;
 -- end NOT NULL NOT VALID
 -- Comments

src/test/regress/sql/constraints.sql

@@ -997,6 +997,9 @@ create table constr_parent3 (a int not null);
 create table constr_child3 () inherits (constr_parent2, constr_parent3);
 EXECUTE get_nnconstraint_info('{constr_parent3, constr_child3}');
 
+COMMENT ON CONSTRAINT constr_parent2_a_not_null ON constr_parent2 IS 'this constraint is invalid';
+COMMENT ON CONSTRAINT constr_parent2_a_not_null ON constr_child2 IS 'this constraint is valid';
+
 DEALLOCATE get_nnconstraint_info;
 
 -- end NOT NULL NOT VALID