executor: return error if autoid overflows shard bits. (#8936)

pingcap · Jan 8, 2019 · 106bc7e · 106bc7e
1 parent 8468e7e
commit 106bc7e
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diff --git a/executor/ddl_test.go b/executor/ddl_test.go
@@ -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"
@@ -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) {

diff --git a/table/tables/tables.go b/table/tables/tables.go
@@ -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)
@@ -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)