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planner: fix unique key get wrong row count when to query the NULL value | tidb-test=pr/2476 #56277

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merged 2 commits into from
Feb 5, 2025
Merged

planner: fix unique key get wrong row count when to query the NULL value | tidb-test=pr/2476 #56277

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1b59447
This is an automated cherry-pick of #56117
hawkingrei Sep 19, 2024
8f0be27
update
hawkingrei Feb 5, 2025
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6 changes: 4 additions & 2 deletions statistics/index.go
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Original file line number Diff line number Diff line change
Expand Up @@ -240,8 +240,10 @@ func (idx *Index) GetRowCount(sctx sessionctx.Context, coll *HistColl, indexRang
if fullLen {
// At most 1 in this case.
if idx.Info.Unique {
totalCount++
continue
if !indexRange.IsOnlyNull() {
totalCount++
continue
}
}
count = idx.equalRowCount(lb, realtimeRowCount)
// If the current table row count has changed, we should scale the row count accordingly.
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15 changes: 15 additions & 0 deletions statistics/integration_test.go
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Expand Up @@ -808,3 +808,18 @@ func TestIssue49986(t *testing.T) {
" └─Selection 10.00 cop[tikv] eq(\"astp2019121731703151\", test.acc.m)",
" └─TableFullScan 10000.00 cop[tikv] table:b keep order:false, stats:pseudo"))
}

func TestIssue56116(t *testing.T) {
store := testkit.CreateMockStore(t)
tk := testkit.NewTestKit(t, store)
tk.MustExec("use test")

tk.MustExec("create table t2(id bigint(20) DEFAULT NULL, UNIQUE KEY index_on_id (id))")
tk.MustExec("insert into t2 values (), (), ()")
tk.MustExec("analyze table t2")
tk.MustQuery("explain select count(*) from t2 where id is null;").Check(testkit.Rows(
"StreamAgg_17 1.00 root funcs:count(Column#5)->Column#3",
"└─IndexReader_18 1.00 root index:StreamAgg_9",
" └─StreamAgg_9 1.00 cop[tikv] funcs:count(1)->Column#5",
" └─IndexRangeScan_16 3.00 cop[tikv] table:t2, index:index_on_id(id) range:[NULL,NULL], keep order:false"))
}
12 changes: 12 additions & 0 deletions util/ranger/types.go
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Expand Up @@ -126,6 +126,18 @@ func (ran *Range) isPoint(stmtCtx *stmtctx.StatementContext, regardNullAsPoint b
return !ran.LowExclude && !ran.HighExclude
}

// IsOnlyNull checks if the range has [NULL, NULL] or [NULL NULL, NULL NULL] range.
func (ran *Range) IsOnlyNull() bool {
for i := range ran.LowVal {
a := ran.LowVal[i]
b := ran.HighVal[i]
if !(a.IsNull() && b.IsNull()) {
return false
}
}
return true
}

// IsPointNonNullable returns if the range is a point without NULL.
func (ran *Range) IsPointNonNullable(sctx sessionctx.Context) bool {
return ran.isPoint(sctx.GetSessionVars().StmtCtx, false)
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