executor: do not acqurie pessimistic lock for non-unique index keys (#36229)

session/tidb_test.go

@@ -68,7 +68,8 @@ func TestParseErrorWarn(t *testing.T) {
 
 func TestKeysNeedLock(t *testing.T) {
  rowKey := tablecodec.EncodeRowKeyWithHandle(1, kv.IntHandle(1))
- indexKey := tablecodec.EncodeIndexSeekKey(1, 1, []byte{1})
+ uniqueIndexKey := tablecodec.EncodeIndexSeekKey(1, 1, []byte{1})
+ nonUniqueIndexKey := tablecodec.EncodeIndexSeekKey(1, 2, []byte{1})
  uniqueValue := make([]byte, 8)
  uniqueUntouched := append(uniqueValue, '1')
  nonUniqueVal := []byte{'0'}
@@ -82,18 +83,20 @@ func TestKeysNeedLock(t *testing.T) {
  }{
  {rowKey, rowVal, true},
  {rowKey, deleteVal, true},
- {indexKey, nonUniqueVal, false},
- {indexKey, nonUniqueUntouched, false},
- {indexKey, uniqueValue, true},
- {indexKey, uniqueUntouched, false},
- {indexKey, deleteVal, false},
+ {nonUniqueIndexKey, nonUniqueVal, false},
+ {nonUniqueIndexKey, nonUniqueUntouched, false},
+ {uniqueIndexKey, uniqueValue, true},
+ {uniqueIndexKey, uniqueUntouched, false},
+ {uniqueIndexKey, deleteVal, false},
  }
 
  for _, test := range tests {
- require.Equal(t, test.need, keyNeedToLock(test.key, test.val, 0))
- }
+ need := keyNeedToLock(test.key, test.val, 0)
+  require.Equal(t, test.need, need)
 
- flag := kv.KeyFlags(1)
- require.True(t, flag.HasPresumeKeyNotExists())
- require.True(t, keyNeedToLock(indexKey, deleteVal, flag))
+ flag := kv.KeyFlags(1)
+ need = keyNeedToLock(test.key, test.val, flag)
+ require.True(t, flag.HasPresumeKeyNotExists())
+ require.True(t, need)
+ }
 }

session/txn.go

@@ -447,9 +447,12 @@ func keyNeedToLock(k, v []byte, flags kv.KeyFlags) bool {
  if tablecodec.IsUntouchedIndexKValue(k, v) {
  return false
  }
- isNonUniqueIndex := tablecodec.IsIndexKey(k) && len(v) == 1
- // Put row key and unique index need to lock.
- return !isNonUniqueIndex
+
+ if !tablecodec.IsIndexKey(k) {
+ return true
+ }
+
+ return tablecodec.IndexKVIsUnique(v)
 }
 
 func getBinlogMutation(ctx sessionctx.Context, tableID int64) *binlog.TableMutation {

tablecodec/tablecodec.go

@@ -1580,3 +1580,16 @@ func decodeIndexKvGeneral(key, value []byte, colsLen int, hdStatus HandleStatus,
  }
  return resultValues, nil
 }
+
+// IndexKVIsUnique uses to judge if an index is unique, it can handle the KV committed by txn already, it doesn't consider the untouched flag.
+func IndexKVIsUnique(value []byte) bool {
+ if len(value) <= MaxOldEncodeValueLen {
+ return len(value) == 8
+ }
+ if getIndexVersion(value) == 1 {
+ segs := SplitIndexValueForClusteredIndexVersion1(value)
+ return segs.CommonHandle != nil
+ }
+ segs := SplitIndexValue(value)
+ return segs.IntHandle != nil || segs.CommonHandle != nil
+}