expression: cast json_extract as bool

expression/expression.go

@@ -455,7 +455,18 @@ func toBool(sc *stmtctx.StatementContext, eType types.EvalType, buf *chunk.Colum
 			}
 		}
 	case types.ETJson:
-		return errors.Errorf("cannot convert type json.BinaryJSON to bool")
+		mysqljsons := buf.MysqlJSONs()
+		for i := range sel {
+			if buf.IsNull(i) {
+				isZero[i] = -1
+			} else {
+				if mysqljsons[i].IsZero() {
+					isZero[i] = 0
+				} else {
+					isZero[i] = 1
+				}
+			}
+		}
 	}
 	return nil
 }

types/datum.go

@@ -1482,6 +1482,9 @@ func (d *Datum) ToBool(sc *stmtctx.StatementContext) (int64, error) {
 	case KindBinaryLiteral, KindMysqlBit:
 		val, err1 := d.GetBinaryLiteral().ToInt(sc)
 		isZero, err = val == 0, err1
+	case KindMysqlJSON:
+		val := d.GetMysqlJSON()
+		isZero = val.IsZero()
 	default:
 		return 0, errors.Errorf("cannot convert %v(type %T) to bool", d.GetValue(), d.GetValue())
 	}

types/json/binary.go

@@ -145,6 +145,28 @@ func (bj BinaryJSON) marshalTo(buf []byte) ([]byte, error) {
 	return buf, nil
 }
 
+//IsZero return a boolean indicate whether BinaryJSON is Zero
+func (bj BinaryJSON) IsZero() bool {
+	isZero := false
+	switch bj.TypeCode {
+	case TypeCodeString:
+		isZero = false
+	case TypeCodeLiteral:
+		isZero = false
+	case TypeCodeInt64:
+		isZero = bj.GetInt64() == 0
+	case TypeCodeUint64:
+		isZero = bj.GetUint64() == 0
+	case TypeCodeFloat64:
+		isZero = bj.GetFloat64() == 0
+	case TypeCodeArray:
+		isZero = false
+	case TypeCodeObject:
+		isZero = false
+	}
+	return isZero
+}
+
 // GetInt64 gets the int64 value.
 func (bj BinaryJSON) GetInt64() int64 {
 	return int64(endian.Uint64(bj.Value))

util/chunk/column.go

@@ -498,6 +498,15 @@ func (c *Column) Times() []types.Time {
 	return res
 }
 
+// MysqlJSONs returns an MysqlJSONs slice stored in this Column.
+func (c *Column) MysqlJSONs() []json.BinaryJSON {
+	var res []json.BinaryJSON
+	for i := 0; i < c.length; i++ {
+		res = append(res, c.GetJSON(i))
+	}
+	return res
+}
+
 // GetInt64 returns the int64 in the specific row.
 func (c *Column) GetInt64(rowID int) int64 {
 	return *(*int64)(unsafe.Pointer(&c.data[rowID*8]))