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*: lock unchanged rows for pessimistic transaction #14045

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merged 4 commits into from
Dec 13, 2019
Merged

*: lock unchanged rows for pessimistic transaction #14045

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863eb3f
*: lock unchanged row keys for update statement in pessimistic transa…
coocood Dec 12, 2019
5dac19a
improve test case
coocood Dec 13, 2019
6ac6fda
only add for pessimistic txn
coocood Dec 13, 2019
7a06e8a
Merge branch 'master' into lock-unchanged-updates
sre-bot Dec 13, 2019
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1 change: 1 addition & 0 deletions executor/adapter.go
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Original file line number Diff line number Diff line change
Expand Up @@ -526,6 +526,7 @@ func (a *ExecStmt) handlePessimisticDML(ctx context.Context, e Executor) error {
if err1 != nil {
return err1
}
keys = txnCtx.CollectUnchangedRowKeys(keys)
if len(keys) == 0 {
return nil
}
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6 changes: 6 additions & 0 deletions executor/write.go
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Expand Up @@ -24,6 +24,7 @@ import (
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/table"
"github.com/pingcap/tidb/table/tables"
"github.com/pingcap/tidb/tablecodec"
"github.com/pingcap/tidb/types"
"github.com/pingcap/tidb/util/logutil"
"go.uber.org/zap"
Expand Down Expand Up @@ -123,6 +124,11 @@ func updateRecord(ctx context.Context, sctx sessionctx.Context, h int64, oldData
if sctx.GetSessionVars().ClientCapability&mysql.ClientFoundRows > 0 {
sc.AddAffectedRows(1)
}
unchangedRowKey := tablecodec.EncodeRowKeyWithHandle(t.Meta().ID, h)
txnCtx := sctx.GetSessionVars().TxnCtx
if txnCtx.IsPessimistic {
txnCtx.AddUnchangedRowKey(unchangedRowKey)
}
return false, false, 0, nil
}

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30 changes: 30 additions & 0 deletions session/pessimistic_test.go
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Expand Up @@ -351,6 +351,36 @@ func (s *testPessimisticSuite) TestBankTransfer(c *C) {
tk.MustQuery("select sum(c) from accounts").Check(testkit.Rows("300"))
}

func (s *testPessimisticSuite) TestLockUnchangedRowKey(c *C) {
tk := testkit.NewTestKitWithInit(c, s.store)
tk2 := testkit.NewTestKitWithInit(c, s.store)
tk.MustExec("drop table if exists unchanged")
tk.MustExec("create table unchanged (id int primary key, c int)")
tk.MustExec("insert unchanged values (1, 1), (2, 2)")

tk.MustExec("begin pessimistic")
tk.MustExec("update unchanged set c = 1 where id < 2")

tk2.MustExec("begin pessimistic")
err := tk2.ExecToErr("select * from unchanged where id = 1 for update nowait")
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How long does the lock time out, would it block the CI ?

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No, it returns an error instantly.

c.Assert(err, NotNil)

tk.MustExec("rollback")

tk2.MustQuery("select * from unchanged where id = 1 for update nowait")

tk.MustExec("begin pessimistic")
tk.MustExec("insert unchanged values (2, 2) on duplicate key update c = values(c)")

err = tk2.ExecToErr("select * from unchanged where id = 2 for update nowait")
c.Assert(err, NotNil)

tk.MustExec("commit")

tk2.MustQuery("select * from unchanged where id = 1 for update nowait")
tk2.MustExec("rollback")
}

func (s *testPessimisticSuite) TestOptimisticConflicts(c *C) {
tk := testkit.NewTestKitWithInit(c, s.store)
tk2 := testkit.NewTestKitWithInit(c, s.store)
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20 changes: 20 additions & 0 deletions sessionctx/variable/session.go
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Expand Up @@ -105,6 +105,9 @@ type TransactionContext struct {
Shard *int64
TableDeltaMap map[int64]TableDelta

// unchangedRowKeys is used to store the unchanged rows that needs to lock for pessimistic transaction.
unchangedRowKeys map[string]struct{}

// CreateTime For metrics.
CreateTime time.Time
StatementCount int
Expand All @@ -113,6 +116,23 @@ type TransactionContext struct {
IsPessimistic bool
}

// AddUnchangedRowKey adds an unchanged row key in update statement for pessimistic lock.
func (tc *TransactionContext) AddUnchangedRowKey(key []byte) {
if tc.unchangedRowKeys == nil {
tc.unchangedRowKeys = map[string]struct{}{}
}
tc.unchangedRowKeys[string(key)] = struct{}{}
}

// CollectUnchangedRowKeys collects unchanged row keys for pessimistic lock.
func (tc *TransactionContext) CollectUnchangedRowKeys(buf []kv.Key) []kv.Key {
for key := range tc.unchangedRowKeys {
buf = append(buf, kv.Key(key))
}
tc.unchangedRowKeys = nil
return buf
}

// UpdateDeltaForTable updates the delta info for some table.
func (tc *TransactionContext) UpdateDeltaForTable(tableID int64, delta int64, count int64, colSize map[int64]int64) {
if tc.TableDeltaMap == nil {
Expand Down