Adding mapping to error code 1049 for ErrDatabaseNotFound errors. Map…

…ping errors from ComInitDB to MySQL errors with error codes.

dolthub/dolt#7890

server/handler.go

@@ -90,7 +90,12 @@ func (h *Handler) NewConnection(c *mysql.Conn) {
 }
 
 func (h *Handler) ComInitDB(c *mysql.Conn, schemaName string) error {
-	return h.sm.SetDB(c, schemaName)
+	err := h.sm.SetDB(c, schemaName)
+	if err != nil {
+		logrus.WithField("database", schemaName).Errorf("unable to process ComInitDB: %s", err.Error())
+		err = sql.CastSQLError(err)
+	}
+	return err
 }
 
 // ComPrepare parses, partially analyzes, and caches a prepared statement's plan

server/handler_test.go

@@ -260,6 +260,11 @@ func TestHandlerErrors(t *testing.T) {
 			query:             "INSERT INTO `test`.`test_table` (`id`, `id`, `v`) VALUES (1, 2, 3)",
 			expectedErrorCode: mysql.ERFieldSpecifiedTwice,
 		},
+		{
+			name:              "use database that doesn't exist'",
+			query:             "USE does_not_exist_db;",
+			expectedErrorCode: mysql.ERBadDb,
+		},
 	}
 
 	handler.ComInitDB(dummyConn, "test")

sql/errors.go

@@ -936,6 +936,8 @@ func CastSQLError(err error) *mysql.SQLError {
 		code = mysql.ERNoSuchTable
 	case ErrDatabaseExists.Is(err):
 		code = mysql.ERDbCreateExists
+	case ErrDatabaseNotFound.Is(err):
+		code = mysql.ERBadDb
 	case ErrExpectedSingleRow.Is(err):
 		code = mysql.ERSubqueryNo1Row
 	case ErrInvalidOperandColumns.Is(err):