Add support for create-if-not-exists for 'create schema' (#362)

Author: Cyberax

internal/catalog/build.go

@@ -305,10 +305,12 @@ func Update(c *pg.Catalog, stmt nodes.Node) error {
 	case nodes.CreateSchemaStmt:
 		name := *n.Schemaname
 		if _, exists := c.Schemas[name]; exists {
-			return wrap(pg.ErrorSchemaAlreadyExists(name), raw.StmtLocation)
+			if !n.IfNotExists {
+				return wrap(pg.ErrorSchemaAlreadyExists(name), raw.StmtLocation)
+			}
+		} else {
+			c.Schemas[name] = pg.NewSchema()
 		}
-		c.Schemas[name] = pg.NewSchema()
-
 	case nodes.DropStmt:
 		for _, obj := range n.Objects.Items {
 			if n.RemoveType == nodes.OBJECT_TABLE || n.RemoveType == nodes.OBJECT_TYPE {

internal/endtoend/testdata/builtins/query.sql

@@ -22,3 +22,4 @@ SELECT trunc(42.8);
 SELECT trunc(42.4382, 2);
 SELECT width_bucket(5.35, 0.024, 10.06, 5);
 SELECT width_bucket(now(), array['yesterday', 'today', 'tomorrow']::timestamptz[]);
+create schema if not exists sqlc;