DDL: add two limits for JSON column: used as key and not null default…

… value. (pingcap#3401)

ddl/ddl.go

@@ -73,6 +73,10 @@ var (
 	errBadField              = terror.ClassDDL.New(codeBadField, "Unknown column '%s' in '%s'")
 	errInvalidDefault        = terror.ClassDDL.New(codeInvalidDefault, "Invalid default value for '%s'")
 	errInvalidUseOfNull      = terror.ClassDDL.New(codeInvalidUseOfNull, "Invalid use of NULL value")
+	// errJSONUsedAsKey forbiddens to use JSON as key or index.
+	errJSONUsedAsKey = terror.ClassDDL.New(codeJSONUsedAsKey, mysql.MySQLErrName[mysql.ErrJSONUsedAsKey])
+	// errBlobCantHaveDefault forbiddens to give not null default value to TEXT/BLOB/JSON.
+	errBlobCantHaveDefault = terror.ClassDDL.New(codeBlobCantHaveDefault, mysql.MySQLErrName[mysql.ErrBlobCantHaveDefault])
 
 	// ErrInvalidDBState returns for invalid database state.
 	ErrInvalidDBState = terror.ClassDDL.New(codeInvalidDBState, "invalid database state")
@@ -520,6 +524,8 @@ const (
 	codeInvalidUseOfNull      = 1138
 	codeBlobKeyWithoutLength  = 1170
 	codeInvalidOnUpdate       = 1294
+	codeJSONUsedAsKey         = 3152
+	codeBlobCantHaveDefault   = 1101
 )
 
 func init() {
@@ -541,6 +547,8 @@ func init() {
 		codeBadField:              mysql.ErrBadField,
 		codeInvalidDefault:        mysql.ErrInvalidDefault,
 		codeInvalidUseOfNull:      mysql.ErrInvalidUseOfNull,
+		codeJSONUsedAsKey:         mysql.ErrJSONUsedAsKey,
+		codeBlobCantHaveDefault:   mysql.ErrBlobCantHaveDefault,
 	}
 	terror.ErrClassToMySQLCodes[terror.ClassDDL] = ddlMySQLErrCodes
 }

ddl/ddl_api.go

@@ -224,6 +224,18 @@ func buildColumnAndConstraint(ctx context.Context, offset int,
 	return col, cts, nil
 }
 
+// checkColumnCantHaveDefaultValue checks the column can have value as default or not.
+// Now, TEXT/BLOB/JSON can't have not null value as default.
+func checkColumnCantHaveDefaultValue(col *table.Column, value interface{}) (err error) {
+	if value != nil && (col.Tp == mysql.TypeJSON ||
+		col.Tp == mysql.TypeTinyBlob || col.Tp == mysql.TypeMediumBlob ||
+		col.Tp == mysql.TypeLongBlob || col.Tp == mysql.TypeBlob) {
+		// TEXT/BLOB/JSON can't have not null default values.
+		return errBlobCantHaveDefault.GenByArgs(col.Name.O)
+	}
+	return nil
+}
+
 // columnDefToCol converts ColumnDef to Col and TableConstraints.
 func columnDefToCol(ctx context.Context, offset int, colDef *ast.ColumnDef) (*table.Column, []*ast.Constraint, error) {
 	constraints := []*ast.Constraint{}
@@ -292,6 +304,9 @@ func columnDefToCol(ctx context.Context, offset int, colDef *ast.ColumnDef) (*ta
 				if err != nil {
 					return nil, nil, ErrColumnBadNull.Gen("invalid default value - %s", err)
 				}
+				if err = checkColumnCantHaveDefaultValue(col, value); err != nil {
+					return nil, nil, errors.Trace(err)
+				}
 				col.DefaultValue = value
 				hasDefaultValue = true
 				removeOnUpdateNowFlag(col)
@@ -988,6 +1003,9 @@ func setDefaultAndComment(ctx context.Context, col *table.Column, options []*ast
 			if err != nil {
 				return ErrColumnBadNull.Gen("invalid default value - %s", err)
 			}
+			if err = checkColumnCantHaveDefaultValue(col, value); err != nil {
+				return errors.Trace(err)
+			}
 			col.DefaultValue = value
 			hasDefaultValue = true
 		case ast.ColumnOptionComment:
@@ -1004,7 +1022,6 @@ func setDefaultAndComment(ctx context.Context, col *table.Column, options []*ast
 			if !expression.IsCurrentTimeExpr(opt.Expr) {
 				return ErrInvalidOnUpdate.Gen("invalid ON UPDATE for - %s", col.Name)
 			}
-
 			col.Flag |= mysql.OnUpdateNowFlag
 			setOnUpdateNow = true
 		default:

ddl/index.go

@@ -49,6 +49,11 @@ func buildIndexColumns(columns []*model.ColumnInfo, idxColNames []*ast.IndexColN
 			return nil, errKeyColumnDoesNotExits.Gen("column does not exist: %s", ic.Column.Name)
 		}
 
+		// JSON column cannot index.
+		if col.FieldType.Tp == mysql.TypeJSON {
+			return nil, errors.Trace(errJSONUsedAsKey.GenByArgs(col.Name.O))
+		}
+
 		// Length must be specified for BLOB and TEXT column indexes.
 		if types.IsTypeBlob(col.FieldType.Tp) && ic.Length == types.UnspecifiedLength {
 			return nil, errors.Trace(errBlobKeyWithoutLength)

executor/executor_test.go

@@ -20,6 +20,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/juju/errors"
 	"github.com/ngaut/log"
 	. "github.com/pingcap/check"
 	"github.com/pingcap/tidb"
@@ -28,6 +29,7 @@ import (
 	"github.com/pingcap/tidb/inspectkv"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/model"
+	"github.com/pingcap/tidb/mysql"
 	"github.com/pingcap/tidb/parser"
 	"github.com/pingcap/tidb/plan"
 	"github.com/pingcap/tidb/sessionctx"
@@ -989,6 +991,31 @@ func (s *testSuite) TestJSON(c *C) {
 	result = tk.MustQuery(`select a from test_json tj where a = "string"`)
 	result.Check(testkit.Rows(`"string"`))
 
+	// check some DDL limits for TEXT/BLOB/JSON column.
+	var err error
+	var terr *terror.Error
+
+	_, err = tk.Exec(`create table test_bad_json(a json default '{}')`)
+	c.Assert(err, NotNil)
+	terr = errors.Trace(err).(*errors.Err).Cause().(*terror.Error)
+	c.Assert(terr.Code(), Equals, terror.ErrCode(mysql.ErrBlobCantHaveDefault))
+
+	_, err = tk.Exec(`create table test_bad_json(a blob default 'hello')`)
+	c.Assert(err, NotNil)
+	terr = errors.Trace(err).(*errors.Err).Cause().(*terror.Error)
+	c.Assert(terr.Code(), Equals, terror.ErrCode(mysql.ErrBlobCantHaveDefault))
+
+	_, err = tk.Exec(`create table test_bad_json(a text default 'world')`)
+	c.Assert(err, NotNil)
+	terr = errors.Trace(err).(*errors.Err).Cause().(*terror.Error)
+	c.Assert(terr.Code(), Equals, terror.ErrCode(mysql.ErrBlobCantHaveDefault))
+
+	// check json fields cannot be used as key.
+	_, err = tk.Exec(`create table test_bad_json(id int, a json, key (a))`)
+	c.Assert(err, NotNil)
+	terr = errors.Trace(err).(*errors.Err).Cause().(*terror.Error)
+	c.Assert(terr.Code(), Equals, terror.ErrCode(mysql.ErrJSONUsedAsKey))
+
 	// check CAST AS JSON.
 	result = tk.MustQuery(`select CAST('3' AS JSON), CAST('{}' AS JSON), CAST(null AS JSON)`)
 	result.Check(testkit.Rows(`3 {} <nil>`))

mysql/errcode.go

@@ -885,4 +885,5 @@ const (
 	ErrInvalidJSONText                                              = 3140
 	ErrInvalidJSONPath                                              = 3143
 	ErrInvalidJSONData                                              = 3146
+	ErrJSONUsedAsKey                                                = 3152
 )

mysql/errname.go

@@ -116,7 +116,7 @@ var MySQLErrName = map[uint16]string{
 	ErrNoUniqueLogFile:                          "Can't generate a unique log-filename %-.200s.(1-999)\n",
 	ErrTableNotLockedForWrite:                   "Table '%-.192s' was locked with a READ lock and can't be updated",
 	ErrTableNotLocked:                           "Table '%-.192s' was not locked with LOCK TABLES",
-	ErrBlobCantHaveDefault:                      "BLOB/TEXT column '%-.192s' can't have a default value",
+	ErrBlobCantHaveDefault:                      "BLOB/TEXT/JSON column '%-.192s' can't have a default value",
 	ErrWrongDBName:                              "Incorrect database name '%-.100s'",
 	ErrWrongTableName:                           "Incorrect table name '%-.100s'",
 	ErrTooBigSelect:                             "The SELECT would examine more than MAXJOINSIZE rows; check your WHERE and use SET SQLBIGSELECTS=1 or SET MAXJOINSIZE=# if the SELECT is okay",
@@ -882,4 +882,5 @@ var MySQLErrName = map[uint16]string{
 	ErrInvalidJSONText:                                       "Invalid JSON text: %-.192s",
 	ErrInvalidJSONPath:                                       "Invalid JSON path expression %s.",
 	ErrInvalidJSONData:                                       "Invalid data type for JSON data",
+	ErrJSONUsedAsKey:                                         "JSON column '%-.192s' cannot be used in key specification.",
 }

mysql/state.go

@@ -249,4 +249,5 @@ var MySQLState = map[uint16]string{
 	ErrInvalidJSONText:                     "22032",
 	ErrInvalidJSONPath:                     "42000",
 	ErrInvalidJSONData:                     "22032",
+	ErrJSONUsedAsKey:                       "42000",
 }