>From 7332f3e927b82748398ae4563d23751d0b229499 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Thu, 25 Sep 2014 15:45:04 -0300
Subject: [PATCH 28/42] deparse: support COMMENT ON

---
 src/backend/tcop/deparse_utility.c | 93 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 92 insertions(+), 1 deletion(-)

diff --git a/src/backend/tcop/deparse_utility.c b/src/backend/tcop/deparse_utility.c
index 6110827..9d3ebba 100644
--- a/src/backend/tcop/deparse_utility.c
+++ b/src/backend/tcop/deparse_utility.c
@@ -4026,6 +4026,96 @@ deparse_AlterOwnerStmt(Oid objectId, Node *parsetree)
 	return ownerStmt;
 }
 
+/*
+ * Deparse a CommentStmt when it pertains to a constraint.
+ */
+static ObjTree *
+deparse_CommentOnConstraintSmt(Oid objectId, Node *parsetree)
+{
+	CommentStmt *node = (CommentStmt *) parsetree;
+	ObjTree	   *comment;
+	HeapTuple	constrTup;
+	Form_pg_constraint constrForm;
+	char	   *fmt;
+	ObjectAddress addr;
+
+	Assert(node->objtype == OBJECT_TABCONSTRAINT || node->objtype == OBJECT_DOMCONSTRAINT);
+
+	if (node->comment)
+		fmt = psprintf("COMMENT ON CONSTRAINT %%{identity}s ON %s%%{parentobj}s IS %%{comment}L",
+					   node->objtype == OBJECT_TABCONSTRAINT ? "" : "DOMAIN ");
+	else
+		fmt = psprintf("COMMENT ON CONSTRAINT %%{identity}s ON %s%%{parentobj}s IS NULL",
+					   node->objtype == OBJECT_TABCONSTRAINT ? "" : "DOMAIN ");
+	comment = new_objtree_VA(fmt, 0);
+	if (node->comment)
+		append_string_object(comment, "comment", node->comment);
+
+	constrTup = SearchSysCache1(CONSTROID, objectId);
+	if (!HeapTupleIsValid(constrTup))
+		elog(ERROR, "cache lookup failed for constraint %u", objectId);
+	constrForm = (Form_pg_constraint) GETSTRUCT(constrTup);
+
+	append_string_object(comment, "identity", pstrdup(NameStr(constrForm->conname)));
+
+	if (OidIsValid(constrForm->conrelid))
+	{
+		addr.classId = RelationRelationId;
+		addr.objectId = constrForm->conrelid;
+		addr.objectSubId = 0;
+	}
+	else
+	{
+		addr.classId = TypeRelationId;
+		addr.objectId = constrForm->contypid;
+		addr.objectSubId = 0;
+	}
+
+	append_string_object(comment, "parentobj",
+						 getObjectIdentity(&addr));
+
+	ReleaseSysCache(constrTup);
+
+	return comment;
+}
+
+static ObjTree *
+deparse_CommentStmt(Oid objectId, Oid objectSubId, Node *parsetree)
+{
+	CommentStmt *node = (CommentStmt *) parsetree;
+	ObjTree	   *comment;
+	ObjectAddress addr;
+	char	   *fmt;
+
+	/*
+	 * Constraints are sufficiently different that it is easier to handle them
+	 * separately.
+	 */
+	if (node->objtype == OBJECT_DOMCONSTRAINT ||
+		node->objtype == OBJECT_TABCONSTRAINT)
+		return deparse_CommentOnConstraintSmt(objectId, parsetree);
+
+	if (node->comment)
+		fmt = psprintf("COMMENT ON %s %%{identity}s IS %%{comment}L",
+					   stringify_objtype(node->objtype));
+	else
+		fmt = psprintf("COMMENT ON %s %%{identity}s IS NULL",
+					   stringify_objtype(node->objtype));
+
+	comment = new_objtree_VA(fmt, 0);
+	if (node->comment)
+		append_string_object(comment, "comment", node->comment);
+
+	addr.classId = get_objtype_catalog_oid(node->objtype);
+	addr.objectId = objectId;
+	addr.objectSubId = objectSubId;
+
+	append_string_object(comment, "identity",
+						 getObjectIdentity(&addr));
+
+	return comment;
+}
+
 static ObjTree *
 deparse_CreateConversion(Oid objectId, Node *parsetree)
 {
@@ -4996,7 +5086,8 @@ deparse_simple_command(StashedCommand *cmd)
 			break;
 
 		case T_CommentStmt:
-			command = NULL;
+			command = deparse_CommentStmt(objectId, cmd->d.simple.objectSubId,
+										  parsetree);
 			break;
 
 		case T_GrantStmt:
-- 
2.1.4