planner: fix begin statement consumed read_ts wrongly (#25492) (#25520)

pingcap · Jun 18, 2021 · 38175b9 · 38175b9
1 parent dda34ac
commit 38175b9
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Showing 2 changed files with 11 additions and 1 deletion.
diff --git a/executor/stale_txn_test.go b/executor/stale_txn_test.go
@@ -465,6 +465,14 @@ func (s *testStaleTxnSerialSuite) TestSetTransactionReadOnlyAsOf(c *C) {
 	c.Assert(err, NotNil)
 	c.Assert(err.Error(), Equals, "start transaction read only as of is forbidden after set transaction read only as of")
 	tk.MustExec(`SET TRANSACTION READ ONLY as of timestamp '2021-04-21 00:42:12'`)
+	err = tk.ExecToErr(`START TRANSACTION READ ONLY AS OF TIMESTAMP '2020-09-06 00:00:00'`)
+	c.Assert(err, NotNil)
+	c.Assert(err.Error(), Equals, "start transaction read only as of is forbidden after set transaction read only as of")
+
+	tk.MustExec("begin")
+	c.Assert(tk.Se.GetSessionVars().TxnReadTS.PeakTxnReadTS(), Equals, uint64(424394603102208000))
+	tk.MustExec("commit")
+	tk.MustExec(`START TRANSACTION READ ONLY AS OF TIMESTAMP '2020-09-06 00:00:00'`)
 }
 
 func (s *testStaleTxnSerialSuite) TestValidateReadOnlyInStalenessTransaction(c *C) {

diff --git a/planner/core/planbuilder.go b/planner/core/planbuilder.go
@@ -2447,7 +2447,7 @@ func (b *PlanBuilder) buildSimple(ctx context.Context, node ast.StmtNode) (Plan,
 	case *ast.ShutdownStmt:
 		b.visitInfo = appendVisitInfo(b.visitInfo, mysql.ShutdownPriv, "", "", "", nil)
 	case *ast.BeginStmt:
-		readTS := b.ctx.GetSessionVars().TxnReadTS.UseTxnReadTS()
+		readTS := b.ctx.GetSessionVars().TxnReadTS.PeakTxnReadTS()
 		if raw.AsOf != nil {
 			startTS, err := calculateTsExpr(b.ctx, raw.AsOf)
 			if err != nil {
@@ -2456,6 +2456,8 @@ func (b *PlanBuilder) buildSimple(ctx context.Context, node ast.StmtNode) (Plan,
 			p.StaleTxnStartTS = startTS
 		} else if readTS > 0 {
 			p.StaleTxnStartTS = readTS
+			// consume read ts here
+			b.ctx.GetSessionVars().TxnReadTS.UseTxnReadTS()
 		}
 	}
 	return p, nil