statistics: fix "data too long" error when dumping stats from table w…

…ith new collation data (#27033) (#27300)
pingcap · Sep 3, 2021 · 4bb5d21 · 4bb5d21
1 parent 485415e
commit 4bb5d21
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Showing 2 changed files with 28 additions and 0 deletions.
diff --git a/statistics/handle/handle.go b/statistics/handle/handle.go
@@ -1092,6 +1092,12 @@ func (h *Handle) histogramFromStorage(reader *statsReader, tableID int64, colID
 		} else {
 			sc := &stmtctx.StatementContext{TimeZone: time.UTC}
 			d := rows[i].GetDatum(2, &fields[2].Column.FieldType)
+			// When there's new collation data, the length of bounds of histogram(the collate key) might be
+			// longer than the FieldType.Flen of this column.
+			// We change it to TypeBlob to bypass the length check here.
+			if tp.EvalType() == types.ETString && tp.Tp != mysql.TypeEnum && tp.Tp != mysql.TypeSet {
+				tp = types.NewFieldType(mysql.TypeBlob)
+			}
 			lowerBound, err = d.ConvertTo(sc, tp)
 			if err != nil {
 				return nil, errors.Trace(err)

diff --git a/statistics/handle/handle_test.go b/statistics/handle/handle_test.go
@@ -36,6 +36,7 @@ import (
 	"github.com/pingcap/tidb/store/mockstore"
 	"github.com/pingcap/tidb/store/tikv/oracle"
 	"github.com/pingcap/tidb/types"
+	"github.com/pingcap/tidb/util/collate"
 	"github.com/pingcap/tidb/util/testkit"
 )
 
@@ -2154,3 +2155,24 @@ func (s *testStatsSuite) TestStatsCacheUpdateSkip(c *C) {
 	statsTbl2 := h.GetTableStats(tableInfo)
 	c.Assert(statsTbl1, Equals, statsTbl2)
 }
+
+func (s *testSerialStatsSuite) TestLoadHistogramWithCollate(c *C) {
+	defer cleanEnv(c, s.store, s.do)
+	testKit := testkit.NewTestKit(c, s.store)
+	collate.SetNewCollationEnabledForTest(true)
+	defer collate.SetNewCollationEnabledForTest(false)
+	testKit.MustExec("use test")
+	testKit.MustExec("drop table if exists t")
+	testKit.MustExec("create table t(a varchar(10) collate utf8mb4_unicode_ci);")
+	testKit.MustExec("insert into t values('abcdefghij');")
+	testKit.MustExec("insert into t values('abcdufghij');")
+	testKit.MustExec("analyze table t with 0 topn;")
+	do := s.do
+	h := do.StatsHandle()
+	is := do.InfoSchema()
+	tbl, err := is.TableByName(model.NewCIStr("test"), model.NewCIStr("t"))
+	c.Assert(err, IsNil)
+	tblInfo := tbl.Meta()
+	_, err = h.TableStatsFromStorage(tblInfo, tblInfo.ID, true, 0)
+	c.Assert(err, IsNil)
+}