Improve ALTER DOMAIN / DROP CONSTRAINT with nonexistent constraint

ALTER DOMAIN / DROP CONSTRAINT on a nonexistent constraint name did
not report any error.  Now it reports an error.  The IF EXISTS option
was added to get the usual behavior of ignoring nonexistent objects to
drop.

5 files changed, 32 insertions, 2 deletions

diff --git a/src/backend/commands/typecmds.c b/src/backend/commands/typecmds.c
index 4bbbaf36c93..0f8af31feef 100644
--- a/src/backend/commands/typecmds.c
+++ b/src/backend/commands/typecmds.c
@@ -2264,7 +2264,7 @@ AlterDomainNotNull(List *names, bool notNull)
  */
 void
 AlterDomainDropConstraint(List *names, const char *constrName,
-						  DropBehavior behavior)
+						  DropBehavior behavior, bool missing_ok)
 {
 	TypeName   *typename;
 	Oid			domainoid;
@@ -2274,6 +2274,7 @@ AlterDomainDropConstraint(List *names, const char *constrName,
 	SysScanDesc conscan;
 	ScanKeyData key[1];
 	HeapTuple	contup;
+	bool		found = false;
 
 	/* Make a TypeName so we can use standard type lookup machinery */
 	typename = makeTypeNameFromNameList(names);
@@ -2317,6 +2318,7 @@ AlterDomainDropConstraint(List *names, const char *constrName,
 			conobj.objectSubId = 0;
 
 			performDeletion(&conobj, behavior);
+			found = true;
 		}
 	}
 	/* Clean up after the scan */
@@ -2324,6 +2326,19 @@ AlterDomainDropConstraint(List *names, const char *constrName,
 	heap_close(conrel, RowExclusiveLock);
 
 	heap_close(rel, NoLock);
+
+	if (!found)
+	{
+		if (!missing_ok)
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("constraint \"%s\" of domain \"%s\" does not exist",
+					   constrName, TypeNameToString(typename))));
+		else
+			ereport(NOTICE,
+					(errmsg("constraint \"%s\" of domain \"%s\" does not exist, skipping",
+							constrName, TypeNameToString(typename))));
+	}
 }
 
 /*
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index c9d3e2ee517..756e3a689b8 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2568,6 +2568,7 @@ _copyAlterDomainStmt(const AlterDomainStmt *from)
 	COPY_STRING_FIELD(name);
 	COPY_NODE_FIELD(def);
 	COPY_SCALAR_FIELD(behavior);
+	COPY_SCALAR_FIELD(missing_ok);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index efe2c96fea2..9eff42f707e 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -1034,6 +1034,7 @@ _equalAlterDomainStmt(const AlterDomainStmt *a, const AlterDomainStmt *b)
 	COMPARE_STRING_FIELD(name);
 	COMPARE_NODE_FIELD(def);
 	COMPARE_SCALAR_FIELD(behavior);
+	COMPARE_SCALAR_FIELD(missing_ok);
 
 	return true;
 }
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 29df0c16b3a..87d7305c762 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -7616,6 +7616,18 @@ AlterDomainStmt:
 					n->typeName = $3;
 					n->name = $6;
 					n->behavior = $7;
+					n->missing_ok = false;
+					$$ = (Node *)n;
+				}
+			/* ALTER DOMAIN <domain> DROP CONSTRAINT IF EXISTS <name> [RESTRICT|CASCADE] */
+			| ALTER DOMAIN_P any_name DROP CONSTRAINT IF_P EXISTS name opt_drop_behavior
+				{
+					AlterDomainStmt *n = makeNode(AlterDomainStmt);
+					n->subtype = 'X';
+					n->typeName = $3;
+					n->name = $8;
+					n->behavior = $9;
+					n->missing_ok = true;
 					$$ = (Node *)n;
 				}
 			/* ALTER DOMAIN <domain> VALIDATE CONSTRAINT <name> */
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 923da6a3f30..704bbe9cedf 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -768,7 +768,8 @@ standard_ProcessUtility(Node *parsetree,
 					case 'X':	/* DROP CONSTRAINT */
 						AlterDomainDropConstraint(stmt->typeName,
 												  stmt->name,
-												  stmt->behavior);
+												  stmt->behavior,
+												  stmt->missing_ok);
 						break;
 					case 'V':	/* VALIDATE CONSTRAINT */
 						AlterDomainValidateConstraint(stmt->typeName,