Fix handling of inherited check constraints in ALTER COLUMN TYPE (again).

The previous way of reconstructing check constraints was to do a separate
"ALTER TABLE ONLY tab ADD CONSTRAINT" for each table in an inheritance
hierarchy.  However, that way has no hope of reconstructing the check
constraints' own inheritance properties correctly, as pointed out in
bug #13779 from Jan Dirk Zijlstra.  What we should do instead is to do
a regular "ALTER TABLE", allowing recursion, at the topmost table that
has a particular constraint, and then suppress the work queue entries
for inherited instances of the constraint.

Annoyingly, we'd tried to fix this behavior before, in commit 5ed6546cf,
but we failed to notice that it wasn't reconstructing the pg_constraint
field values correctly.

As long as I'm touching pg_get_constraintdef_worker anyway, tweak it to
always schema-qualify the target table name; this seems like useful backup
to the protections installed by commit 5f173040.

In HEAD/9.5, get rid of get_constraint_relation_oids, which is now unused.
(I could alternatively have modified it to also return conislocal, but that
seemed like a pretty single-purpose API, so let's not pretend it has some
other use.)  It's unused in the back branches as well, but I left it in
place just in case some third-party code has decided to use it.

In HEAD/9.5, also rename pg_get_constraintdef_string to
pg_get_constraintdef_command, as the previous name did nothing to explain
what that entry point did differently from others (and its comment was
equally useless).  Again, that change doesn't seem like material for
back-patching.

I did a bit of re-pgindenting in tablecmds.c in HEAD/9.5, as well.

Otherwise, back-patch to all supported branches.

3 files changed, 80 insertions, 65 deletions

diff --git a/src/backend/catalog/pg_constraint.c b/src/backend/catalog/pg_constraint.c
index 3c756f82278..95bf08f716a 100644
--- a/src/backend/catalog/pg_constraint.c
+++ b/src/backend/catalog/pg_constraint.c
@@ -754,25 +754,6 @@ AlterConstraintNamespaces(Oid ownerId, Oid oldNspId,
 }
 
 /*
- * get_constraint_relation_oids
- *		Find the IDs of the relations to which a constraint refers.
- */
-void
-get_constraint_relation_oids(Oid constraint_oid, Oid *conrelid, Oid *confrelid)
-{
-	HeapTuple	tup;
-	Form_pg_constraint con;
-
-	tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constraint_oid));
-	if (!HeapTupleIsValid(tup)) /* should not happen */
-		elog(ERROR, "cache lookup failed for constraint %u", constraint_oid);
-	con = (Form_pg_constraint) GETSTRUCT(tup);
-	*conrelid = con->conrelid;
-	*confrelid = con->confrelid;
-	ReleaseSysCache(tup);
-}
-
-/*
  * get_relation_constraint_oid
  *		Find a constraint on the specified relation with the specified name.
  *		Returns constraint's OID.
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index c5bfee68a5a..15ca5ec9569 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -3519,7 +3519,7 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 										 * constraint */
 			address =
 				ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
-									false, true, lockmode);
+									true, true, lockmode);
 			break;
 		case AT_ReAddComment:	/* Re-add existing comment */
 			address = CommentObject((CommentStmt *) cmd->def);
@@ -6072,13 +6072,6 @@ ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
  * AddRelationNewConstraints would normally assign different names to the
  * child constraints.  To fix that, we must capture the name assigned at
  * the parent table and pass that down.
- *
- * When re-adding a previously existing constraint (during ALTER COLUMN TYPE),
- * we don't need to recurse here, because recursion will be carried out at a
- * higher level; the constraint name issue doesn't apply because the names
- * have already been assigned and are just being re-used.  We need a separate
- * "is_readd" flag for that; just setting recurse=false would result in an
- * error if there are child tables.
  */
 static ObjectAddress
 ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
@@ -6107,7 +6100,7 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	 */
 	newcons = AddRelationNewConstraints(rel, NIL,
 										list_make1(copyObject(constr)),
-										recursing,		/* allow_merge */
+										recursing | is_readd,	/* allow_merge */
 										!recursing,		/* is_local */
 										is_readd);		/* is_internal */
 
@@ -6156,10 +6149,8 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 
 	/*
 	 * If adding a NO INHERIT constraint, no need to find our children.
-	 * Likewise, in a re-add operation, we don't need to recurse (that will be
-	 * handled at higher levels).
 	 */
-	if (constr->is_no_inherit || is_readd)
+	if (constr->is_no_inherit)
 		return address;
 
 	/*
@@ -8191,7 +8182,7 @@ ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
 				if (!list_member_oid(tab->changedConstraintOids,
 									 foundObject.objectId))
 				{
-					char	   *defstring = pg_get_constraintdef_string(foundObject.objectId);
+					char	   *defstring = pg_get_constraintdef_command(foundObject.objectId);
 
 					/*
 					 * Put NORMAL dependencies at the front of the list and
@@ -8566,10 +8557,30 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
 			def_item, tab->changedConstraintDefs)
 	{
 		Oid			oldId = lfirst_oid(oid_item);
+		HeapTuple	tup;
+		Form_pg_constraint con;
 		Oid			relid;
 		Oid			confrelid;
+		bool		conislocal;
+
+		tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(oldId));
+		if (!HeapTupleIsValid(tup))		/* should not happen */
+			elog(ERROR, "cache lookup failed for constraint %u", oldId);
+		con = (Form_pg_constraint) GETSTRUCT(tup);
+		relid = con->conrelid;
+		confrelid = con->confrelid;
+		conislocal = con->conislocal;
+		ReleaseSysCache(tup);
+
+		/*
+		 * If the constraint is inherited (only), we don't want to inject a
+		 * new definition here; it'll get recreated when ATAddCheckConstraint
+		 * recurses from adding the parent table's constraint.  But we had to
+		 * carry the info this far so that we can drop the constraint below.
+		 */
+		if (!conislocal)
+			continue;
 
-		get_constraint_relation_oids(oldId, &relid, &confrelid);
 		ATPostAlterTypeParse(oldId, relid, confrelid,
 							 (char *) lfirst(def_item),
 							 wqueue, lockmode, tab->rewrite);
@@ -8743,7 +8754,7 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
 											 rel, con->conname);
 				}
 				else
-					elog(ERROR, "unexpected statement type: %d",
+					elog(ERROR, "unexpected statement subtype: %d",
 						 (int) cmd->subtype);
 			}
 		}
@@ -11254,9 +11265,9 @@ ATPrepChangePersistence(Relation rel, bool toLogged)
 				if (foreignrel->rd_rel->relpersistence != RELPERSISTENCE_PERMANENT)
 					ereport(ERROR,
 							(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
-						 errmsg("could not change table \"%s\" to logged because it references unlogged table \"%s\"",
-								RelationGetRelationName(rel),
-								RelationGetRelationName(foreignrel)),
+							 errmsg("could not change table \"%s\" to logged because it references unlogged table \"%s\"",
+									RelationGetRelationName(rel),
+									RelationGetRelationName(foreignrel)),
 							 errtableconstraint(rel, NameStr(con->conname))));
 			}
 			else
@@ -11264,9 +11275,9 @@ ATPrepChangePersistence(Relation rel, bool toLogged)
 				if (foreignrel->rd_rel->relpersistence == RELPERSISTENCE_PERMANENT)
 					ereport(ERROR,
 							(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
-					   errmsg("could not change table \"%s\" to unlogged because it references logged table \"%s\"",
-							  RelationGetRelationName(rel),
-							  RelationGetRelationName(foreignrel)),
+							 errmsg("could not change table \"%s\" to unlogged because it references logged table \"%s\"",
+									RelationGetRelationName(rel),
+									RelationGetRelationName(foreignrel)),
 							 errtableconstraint(rel, NameStr(con->conname))));
 			}
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 771b14b48ac..0ab839dc736 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -433,6 +433,7 @@ static Node *processIndirection(Node *node, deparse_context *context,
 static void printSubscripts(ArrayRef *aref, deparse_context *context);
 static char *get_relation_name(Oid relid);
 static char *generate_relation_name(Oid relid, List *namespaces);
+static char *generate_qualified_relation_name(Oid relid);
 static char *generate_function_name(Oid funcid, int nargs,
 					   List *argnames, Oid *argtypes,
 					   bool has_variadic, bool *use_variadic_p,
@@ -1314,9 +1315,11 @@ pg_get_constraintdef_ext(PG_FUNCTION_ARGS)
 															  prettyFlags)));
 }
 
-/* Internal version that returns a palloc'd C string; no pretty-printing */
+/*
+ * Internal version that returns a full ALTER TABLE ... ADD CONSTRAINT command
+ */
 char *
-pg_get_constraintdef_string(Oid constraintId)
+pg_get_constraintdef_command(Oid constraintId)
 {
 	return pg_get_constraintdef_worker(constraintId, true, 0);
 }
@@ -1363,10 +1366,16 @@ pg_get_constraintdef_worker(Oid constraintId, bool fullCommand,
 
 	initStringInfo(&buf);
 
-	if (fullCommand && OidIsValid(conForm->conrelid))
+	if (fullCommand)
 	{
-		appendStringInfo(&buf, "ALTER TABLE ONLY %s ADD CONSTRAINT %s ",
-						 generate_relation_name(conForm->conrelid, NIL),
+		/*
+		 * Currently, callers want ALTER TABLE (without ONLY) for CHECK
+		 * constraints, and other types of constraints don't inherit anyway so
+		 * it doesn't matter whether we say ONLY or not.  Someday we might
+		 * need to let callers specify whether to put ONLY in the command.
+		 */
+		appendStringInfo(&buf, "ALTER TABLE %s ADD CONSTRAINT %s ",
+						 generate_qualified_relation_name(conForm->conrelid),
 						 quote_identifier(NameStr(conForm->conname)));
 	}
 
@@ -1890,28 +1899,9 @@ pg_get_serial_sequence(PG_FUNCTION_ARGS)
 
 	if (OidIsValid(sequenceId))
 	{
-		HeapTuple	classtup;
-		Form_pg_class classtuple;
-		char	   *nspname;
 		char	   *result;
 
-		/* Get the sequence's pg_class entry */
-		classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(sequenceId));
-		if (!HeapTupleIsValid(classtup))
-			elog(ERROR, "cache lookup failed for relation %u", sequenceId);
-		classtuple = (Form_pg_class) GETSTRUCT(classtup);
-
-		/* Get the namespace */
-		nspname = get_namespace_name(classtuple->relnamespace);
-		if (!nspname)
-			elog(ERROR, "cache lookup failed for namespace %u",
-				 classtuple->relnamespace);
-
-		/* And construct the result string */
-		result = quote_qualified_identifier(nspname,
-											NameStr(classtuple->relname));
-
-		ReleaseSysCache(classtup);
+		result = generate_qualified_relation_name(sequenceId);
 
 		PG_RETURN_TEXT_P(string_to_text(result));
 	}
@@ -9578,6 +9568,39 @@ generate_relation_name(Oid relid, List *namespaces)
 }
 
 /*
+ * generate_qualified_relation_name
+ *		Compute the name to display for a relation specified by OID
+ *
+ * As above, but unconditionally schema-qualify the name.
+ */
+static char *
+generate_qualified_relation_name(Oid relid)
+{
+	HeapTuple	tp;
+	Form_pg_class reltup;
+	char	   *relname;
+	char	   *nspname;
+	char	   *result;
+
+	tp = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
+	if (!HeapTupleIsValid(tp))
+		elog(ERROR, "cache lookup failed for relation %u", relid);
+	reltup = (Form_pg_class) GETSTRUCT(tp);
+	relname = NameStr(reltup->relname);
+
+	nspname = get_namespace_name(reltup->relnamespace);
+	if (!nspname)
+		elog(ERROR, "cache lookup failed for namespace %u",
+			 reltup->relnamespace);
+
+	result = quote_qualified_identifier(nspname, relname);
+
+	ReleaseSysCache(tp);
+
+	return result;
+}
+
+/*
  * generate_function_name
  *		Compute the name to display for a function specified by OID,
  *		given that it is being called with the specified actual arg names and