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executor: return error if autoid overflow to shard bits. #8936

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Jan 8, 2019
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19 changes: 19 additions & 0 deletions executor/ddl_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ import (
"github.com/pingcap/parser/terror"
"github.com/pingcap/tidb/ddl"
"github.com/pingcap/tidb/domain"
"github.com/pingcap/tidb/meta/autoid"
plannercore "github.com/pingcap/tidb/planner/core"
"github.com/pingcap/tidb/sessionctx/variable"
"github.com/pingcap/tidb/table"
Expand Down Expand Up @@ -469,6 +470,24 @@ func (s *testSuite3) TestShardRowIDBits(c *C) {
_, err = tk.Exec("alter table auto shard_row_id_bits = 4")
c.Assert(err, NotNil)
tk.MustExec("alter table auto shard_row_id_bits = 0")

// Test overflow
tk.MustExec("drop table if exists t1")
tk.MustExec("create table t1 (a int) shard_row_id_bits = 15")
defer tk.MustExec("drop table if exists t1")

tbl, err = domain.GetDomain(tk.Se).InfoSchema().TableByName(model.NewCIStr("test"), model.NewCIStr("t1"))
c.Assert(err, IsNil)
maxID := 1<<(64-15-1) - 1
err = tbl.RebaseAutoID(tk.Se, int64(maxID)-1, false)
c.Assert(err, IsNil)
tk.MustExec("insert into t1 values(1)")

// continue inserting will fail.
_, err = tk.Exec("insert into t1 values(2)")
c.Assert(autoid.ErrAutoincReadFailed.Equal(err), IsTrue, Commentf("err:%v", err))
_, err = tk.Exec("insert into t1 values(3)")
c.Assert(autoid.ErrAutoincReadFailed.Equal(err), IsTrue, Commentf("err:%v", err))
}

func (s *testSuite3) TestMaxHandleAddIndex(c *C) {
Expand Down
16 changes: 16 additions & 0 deletions table/tables/tables.go
Original file line number Diff line number Diff line change
Expand Up @@ -919,6 +919,16 @@ func (t *tableCommon) AllocAutoID(ctx sessionctx.Context) (int64, error) {
return 0, errors.Trace(err)
}
if t.meta.ShardRowIDBits > 0 {
if t.overflowShardBits(rowID) {
// If overflow, the rowID may be duplicated. For examples,
// t.meta.ShardRowIDBits = 4
// rowID = 0010111111111111111111111111111111111111111111111111111111111111
// shard = 01000000000000000000000000000000000000000000000000000000000000000
// will be duplicated with:
// rowID = 0100111111111111111111111111111111111111111111111111111111111111
// shard = 0010000000000000000000000000000000000000000000000000000000000000
return 0, autoid.ErrAutoincReadFailed
}
txnCtx := ctx.GetSessionVars().TxnCtx
if txnCtx.Shard == nil {
shard := t.calcShard(txnCtx.StartTS)
Expand All @@ -929,6 +939,12 @@ func (t *tableCommon) AllocAutoID(ctx sessionctx.Context) (int64, error) {
return rowID, nil
}

// overflowShardBits check whether the rowID overflow `1<<(64-t.meta.ShardRowIDBits-1) -1`.
func (t *tableCommon) overflowShardBits(rowID int64) bool {
mask := (1<<t.meta.ShardRowIDBits - 1) << (64 - t.meta.ShardRowIDBits - 1)
return rowID&int64(mask) > 0
}

func (t *tableCommon) calcShard(startTS uint64) int64 {
var buf [8]byte
binary.LittleEndian.PutUint64(buf[:], startTS)
Expand Down