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stats: fix panic caused by empty histogram (#7912) #7927

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merged 1 commit into from
Oct 17, 2018
Merged

stats: fix panic caused by empty histogram (#7912) #7927

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2 changes: 1 addition & 1 deletion statistics/histogram.go
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Original file line number Diff line number Diff line change
Expand Up @@ -616,7 +616,7 @@ func MergeHistograms(sc *stmtctx.StatementContext, lh *Histogram, rh *Histogram,
}

func (hg *Histogram) outOfRange(val types.Datum) bool {
if hg.Bounds == nil {
if hg.Len() == 0 {
return true
}
len := hg.Bounds.NumRows()
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12 changes: 12 additions & 0 deletions statistics/selectivity_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -267,6 +267,18 @@ func (s *testSelectivitySuite) TestEstimationForUnknownValues(c *C) {
count, err = statsTbl.GetRowCountByIndexRanges(sc, idxID, getRange(9, 30))
c.Assert(err, IsNil)
c.Assert(count, Equals, 2.2)

testKit.MustExec("truncate table t")
testKit.MustExec("insert into t values (null, null)")
testKit.MustExec("analyze table t")
table, err = s.dom.InfoSchema().TableByName(model.NewCIStr("test"), model.NewCIStr("t"))
c.Assert(err, IsNil)
statsTbl = h.GetTableStats(table.Meta())

colID = table.Meta().Columns[0].ID
count, err = statsTbl.GetRowCountByColumnRanges(sc, colID, getRange(1, 30))
c.Assert(err, IsNil)
c.Assert(count, Equals, 0.0)
}

func BenchmarkSelectivity(b *testing.B) {
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