add parsing & ast for vexplain trace

Signed-off-by: Andres Taylor <[email protected]>

go/vt/sqlparser/ast_funcs.go

@@ -1923,6 +1923,8 @@ func (ty VExplainType) ToString() string {
 		return QueriesStr
 	case AllVExplainType:
 		return AllVExplainStr
+	case TraceVExplainType:
+		return TraceStr
 	default:
 		return "Unknown VExplainType"
 	}

go/vt/sqlparser/constants.go

@@ -276,6 +276,7 @@ const (
 	QueriesStr     = "queries"
 	AllVExplainStr = "all"
 	PlanStr        = "plan"
+	TraceStr       = "trace"
 
 	// Lock Types
 	ReadStr             = "read"
@@ -846,6 +847,7 @@ const (
 	QueriesVExplainType VExplainType = iota
 	PlanVExplainType
 	AllVExplainType
+	TraceVExplainType
 )
 
 // Constant for Enum Type - SelectIntoType

go/vt/sqlparser/keywords.go

@@ -711,6 +711,7 @@ var keywords = []keyword{
 	{"tinyint", TINYINT},
 	{"tinytext", TINYTEXT},
 	{"to", TO},
+	{"trace", TRACE},
 	{"trailing", TRAILING},
 	{"transaction", TRANSACTION},
 	{"transactions", TRANSACTIONS},

go/vt/sqlparser/parse_test.go

@@ -2567,6 +2567,9 @@ var (
 	}, {
 		input:  "vexplain select * from t",
 		output: "vexplain plan select * from t",
+	}, {
+		input:  "vexplain trace select * from t",
+		output: "vexplain trace select * from t",
 	}, {
 		input: "explain analyze select * from t",
 	}, {