planner, ddl: convert large varchar for create table in non strict mode

ddl/column_test.go

@@ -1193,8 +1193,8 @@ func (s *testColumnSuite) TestModifyColumn(c *C) {
 		{"decimal(2,1)", "bigint", nil},
 	}
 	for _, tt := range tests {
-		ftA := s.colDefStrToFieldType(c, tt.origin)
-		ftB := s.colDefStrToFieldType(c, tt.to)
+		ftA := s.colDefStrToFieldType(c, tt.origin, ctx)
+		ftB := s.colDefStrToFieldType(c, tt.to, ctx)
 		err := checkModifyTypes(ctx, ftA, ftB, false)
 		if err == nil {
 			c.Assert(tt.err, IsNil, Commentf("origin:%v, to:%v", tt.origin, tt.to))
@@ -1204,13 +1204,13 @@ func (s *testColumnSuite) TestModifyColumn(c *C) {
 	}
 }
 
-func (s *testColumnSuite) colDefStrToFieldType(c *C, str string) *types.FieldType {
+func (s *testColumnSuite) colDefStrToFieldType(c *C, str string, ctx sessionctx.Context) *types.FieldType {
 	sqlA := "alter table t modify column a " + str
 	stmt, err := parser.New().ParseOneStmt(sqlA, "", "")
 	c.Assert(err, IsNil)
 	colDef := stmt.(*ast.AlterTableStmt).Specs[0].NewColumns[0]
 	chs, coll := charset.GetDefaultCharsetAndCollate()
-	col, _, err := buildColumnAndConstraint(nil, 0, colDef, nil, chs, coll)
+	col, _, err := buildColumnAndConstraint(ctx, 0, colDef, nil, chs, coll)
 	c.Assert(err, IsNil)
 	return &col.FieldType
 }

ddl/ddl_api.go

@@ -587,6 +587,22 @@ func buildColumnAndConstraint(
 	if err := setCharsetCollationFlenDecimal(colDef.Tp, chs, coll); err != nil {
 		return nil, nil, errors.Trace(err)
 	}
+	// Some column checks are left here, so varchar auto convert is performed. See also issue 30328
+	sessVars := ctx.GetSessionVars()
+	if sessVars != nil && !sessVars.SQLMode.HasStrictMode() && colDef.Tp.Tp == mysql.TypeVarchar {
+		err := IsTooBigFieldLength(colDef.Tp.Flen, colDef.Name.Name.O, colDef.Tp.Charset)
+		if err != nil && terror.ErrorEqual(types.ErrTooBigFieldLength, err) {
+			colDef.Tp.Tp = mysql.TypeBlob
+			if err = adjustBlobTypesFlen(colDef.Tp, colDef.Tp.Charset); err != nil {
+				return nil, nil, err
+			}
+			if colDef.Tp.Charset == charset.CharsetBin {
+				sessVars.StmtCtx.AppendWarning(ErrAutoConvert.GenWithStackByArgs(colDef.Name.Name.O, "VARBINARY", "BLOB"))
+			} else {
+				sessVars.StmtCtx.AppendWarning(ErrAutoConvert.GenWithStackByArgs(colDef.Name.Name.O, "VARCHAR", "TEXT"))
+			}
+		}
+	}
 	col, cts, err := columnDefToCol(ctx, offset, colDef, outPriKeyConstraint)
 	if err != nil {
 		return nil, nil, errors.Trace(err)

ddl/error.go

@@ -310,4 +310,7 @@ var (
 	errDependentByFunctionalIndex = dbterror.ClassDDL.NewStd(mysql.ErrDependentByFunctionalIndex)
 	// errFunctionalIndexOnBlob when the expression of expression index returns blob or text.
 	errFunctionalIndexOnBlob = dbterror.ClassDDL.NewStd(mysql.ErrFunctionalIndexOnBlob)
+
+	// ErrAutoConvert is returned when auto convert happens
+	ErrAutoConvert = dbterror.ClassDDL.NewStd(mysql.ErrAutoConvert)
 )

errors.toml

@@ -361,6 +361,11 @@ error = '''
 Incorrect usage of %s and %s
 '''
 
+["ddl:1246"]
+error = '''
+Converting column '%s' from %s to %s
+'''
+
 ["ddl:1248"]
 error = '''
 Every derived table must have its own alias

planner/core/preprocess.go

@@ -30,6 +30,7 @@ import (
 	"github.com/pingcap/tidb/meta/autoid"
 	"github.com/pingcap/tidb/parser"
 	"github.com/pingcap/tidb/parser/ast"
+	"github.com/pingcap/tidb/parser/charset"
 	"github.com/pingcap/tidb/parser/format"
 	"github.com/pingcap/tidb/parser/model"
 	"github.com/pingcap/tidb/parser/mysql"
@@ -782,8 +783,20 @@ func (p *preprocessor) checkCreateTableGrammar(stmt *ast.CreateTableStmt) {
 	countPrimaryKey := 0
 	for _, colDef := range stmt.Cols {
 		if err := checkColumn(colDef); err != nil {
-			p.err = err
-			return
+			if !p.ctx.GetSessionVars().SQLMode.HasStrictMode() &&
+				colDef.Tp.Tp == mysql.TypeVarchar && colDef.Tp.Charset != "" &&
+				terror.ErrorEqual(err, types.ErrTooBigFieldLength) {
+				// Convert to BLOB or TEXT, see also issue 30328
+				colDef.Tp.Tp = mysql.TypeBlob
+				if colDef.Tp.Charset == charset.CharsetBin {
+					p.ctx.GetSessionVars().StmtCtx.AppendWarning(ddl.ErrAutoConvert.GenWithStackByArgs(colDef.Name.Name.O, "VARBINARY", "BLOB"))
+				} else {
+					p.ctx.GetSessionVars().StmtCtx.AppendWarning(ddl.ErrAutoConvert.GenWithStackByArgs(colDef.Name.Name.O, "VARCHAR", "TEXT"))
+				}
+			} else {
+				p.err = err
+				return
+			}
 		}
 		isPrimary, err := checkColumnOptions(stmt.TemporaryKeyword != ast.TemporaryNone, colDef.Options)
 		if err != nil {

planner/core/preprocess_test.go

@@ -364,3 +364,27 @@ func (s *testValidatorSuite) TestDropGlobalTempTable(c *C) {
 	s.runSQL(c, "drop global temporary table temp, ltemp1", false, core.ErrDropTableOnTemporaryTable)
 	s.runSQL(c, "drop global temporary table test2.temp2, temp1", false, nil)
 }
+
+// For issue 30328
+func (s *testValidatorSuite) TestLargeVarcharAutoConv(c *C) {
+	_, err := s.se.Execute(context.Background(), "use test")
+	c.Assert(err, IsNil)
+	s.runSQL(c, "CREATE TABLE t1(a varbinary(70000), b varchar(70000000))", false,
+		errors.New("[types:1074]Column length too big for column 'a' (max = 65535); use BLOB or TEXT instead"))
+
+	_, err = s.se.Execute(context.Background(), "SET sql_mode = 'NO_ENGINE_SUBSTITUTION'")
+	c.Assert(err, IsNil)
+	s.runSQL(c, "CREATE TABLE t1(a varbinary(70000), b varchar(70000000));", false, nil)
+	s.runSQL(c, "CREATE TABLE t1(a varbinary(70000), b varchar(70000000) charset utf8mb4);", false, nil)
+	warnCnt := s.se.GetSessionVars().StmtCtx.WarningCount()
+	// It is only 3 as for first stmt, ddl will append a warning for column b
+	c.Assert(warnCnt, Equals, uint16(3))
+	warns := s.se.GetSessionVars().StmtCtx.GetWarnings()
+	for i := range warns {
+		c.Assert(terror.ErrorEqual(warns[i].Err, ddl.ErrAutoConvert), IsTrue)
+	}
+
+	s.se.GetSessionVars().StmtCtx.SetWarnings(warns[:0])
+	_, err = s.se.Execute(context.Background(), "SET sql_mode = 'STRICT_TRANS_TABLES,NO_ENGINE_SUBSTITUTION'")
+	c.Assert(err, IsNil)
+}