expression: do not set ParseToJSONFlag to a JSON column (#8564)

expression/builtin_compare.go

@@ -1169,7 +1169,7 @@ func (c *compareFunctionClass) generateCmpSigs(ctx sessionctx.Context, args []Ex
 	if tp == types.ETJson {
 		// In compare, if we cast string to JSON, we shouldn't parse it.
 		for i := range args {
-			args[i].GetType().Flag &= ^mysql.ParseToJSONFlag
+			DisableParseJSONFlag4Expr(args[i])
 		}
 	}
 	bf.tp.Flen = 1

expression/builtin_json.go

@@ -16,7 +16,6 @@ package expression
 import (
 	"github.com/pingcap/errors"
 	"github.com/pingcap/parser/ast"
-	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/types"
 	"github.com/pingcap/tidb/types/json"
@@ -174,7 +173,7 @@ func (c *jsonUnquoteFunctionClass) getFunction(ctx sessionctx.Context, args []Ex
 		return nil, err
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETString, types.ETJson)
-	args[0].GetType().Flag &= ^mysql.ParseToJSONFlag
+	DisableParseJSONFlag4Expr(args[0])
 	sig := &builtinJSONUnquoteSig{bf}
 	sig.setPbCode(tipb.ScalarFuncSig_JsonUnquoteSig)
 	return sig, nil
@@ -218,7 +217,7 @@ func (c *jsonSetFunctionClass) getFunction(ctx sessionctx.Context, args []Expres
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETJson, argTps...)
 	for i := 2; i < len(args); i += 2 {
-		args[i].GetType().Flag &= ^mysql.ParseToJSONFlag
+		DisableParseJSONFlag4Expr(args[i])
 	}
 	sig := &builtinJSONSetSig{bf}
 	sig.setPbCode(tipb.ScalarFuncSig_JsonSetSig)
@@ -258,7 +257,7 @@ func (c *jsonInsertFunctionClass) getFunction(ctx sessionctx.Context, args []Exp
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETJson, argTps...)
 	for i := 2; i < len(args); i += 2 {
-		args[i].GetType().Flag &= ^mysql.ParseToJSONFlag
+		DisableParseJSONFlag4Expr(args[i])
 	}
 	sig := &builtinJSONInsertSig{bf}
 	sig.setPbCode(tipb.ScalarFuncSig_JsonInsertSig)
@@ -298,7 +297,7 @@ func (c *jsonReplaceFunctionClass) getFunction(ctx sessionctx.Context, args []Ex
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETJson, argTps...)
 	for i := 2; i < len(args); i += 2 {
-		args[i].GetType().Flag &= ^mysql.ParseToJSONFlag
+		DisableParseJSONFlag4Expr(args[i])
 	}
 	sig := &builtinJSONReplaceSig{bf}
 	sig.setPbCode(tipb.ScalarFuncSig_JsonReplaceSig)
@@ -434,7 +433,7 @@ func (c *jsonObjectFunctionClass) getFunction(ctx sessionctx.Context, args []Exp
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETJson, argTps...)
 	for i := 1; i < len(args); i += 2 {
-		args[i].GetType().Flag &= ^mysql.ParseToJSONFlag
+		DisableParseJSONFlag4Expr(args[i])
 	}
 	sig := &builtinJSONObjectSig{bf}
 	sig.setPbCode(tipb.ScalarFuncSig_JsonObjectSig)
@@ -497,7 +496,7 @@ func (c *jsonArrayFunctionClass) getFunction(ctx sessionctx.Context, args []Expr
 	}
 	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETJson, argTps...)
 	for i := range args {
-		args[i].GetType().Flag &= ^mysql.ParseToJSONFlag
+		DisableParseJSONFlag4Expr(args[i])
 	}
 	sig := &builtinJSONArraySig{bf}
 	sig.setPbCode(tipb.ScalarFuncSig_JsonArraySig)

expression/util.go

@@ -528,6 +528,18 @@ func GetParamExpression(ctx sessionctx.Context, v *driver.ParamMarkerExpr) (Expr
 	return value, nil
 }
 
+// DisableParseJSONFlag4Expr disables ParseToJSONFlag for `expr` except Column.
+// We should not *PARSE* a string as JSON under some scenarios. ParseToJSONFlag
+// is 0 for JSON column yet, so we can skip it. Moreover, Column.RetType refers
+// to the infoschema, if we modify it, data race may happen if another goroutine
+// read from the infoschema at the same time.
+func DisableParseJSONFlag4Expr(expr Expression) {
+	if _, isColumn := expr.(*Column); isColumn {
+		return
+	}
+	expr.GetType().Flag &= ^mysql.ParseToJSONFlag
+}
+
 // ConstructPositionExpr constructs PositionExpr with the given ParamMarkerExpr.
 func ConstructPositionExpr(p *driver.ParamMarkerExpr) *ast.PositionExpr {
 	return &ast.PositionExpr{P: p}