stats: fix row estimation for pseudo unique key #6199
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| func PseudoTable(tableID int64) *Table { | ||
| return &Table{ | ||
| TableID: tableID, | ||
| func PseudoTable(tblInfo *model.TableInfo) *Table { |
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Could we cache the pseudo table stats in TableInfo?
statistics/selectivity.go
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| continue | ||
| } | ||
| switch fun.FuncName.L { | ||
| case ast.EQ, ast.NullEQ, ast.In: |
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In and EQ has the same selectivity?
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getConstantColumnID guarantees there exists only two parameters for the current expr, so in is equivalent to eq
statistics/selectivity.go
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| } | ||
| } | ||
| if unique { | ||
| return 1.0 / float64(t.Count) |
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What if the expression is IN with many unique values?
statistics/selectivity.go
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| if len(e) != 2 { | ||
| return false | ||
| return -1 |
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Should get ColumnID in expressions like c in (1, 2, 3)?
|
/run-all-tests |
| if !ok { | ||
| return PseudoTable(tblID) | ||
| tbl = PseudoTable(tblInfo) | ||
| h.UpdateTableStats([]*Table{tbl}, nil) |
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Can we not mix pseudo table with non-pseudo ones by adding pseudoCache in Handle?
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So we don't need to load histograms for pseudo ones.
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But it won't load histograms for pseudo ones.
| @@ -179,7 +182,10 @@ func (h *Handle) UpdateTableStats(tables []*Table, deletedIDs []int64) { | |||
| func (h *Handle) LoadNeededHistograms() error { | |||
| cols := histogramNeededColumns.allCols() | |||
| for _, col := range cols { | |||
| tbl := h.GetTableStats(col.tableID).copy() | |||
| tbl, ok := h.statsCache.Load().(statsCache)[col.tableID] | |||
|
/run-integration-common-test |
zz-jason
added
status/LGT2
If there are equal conditions on the unique key, the row count should not be greater than 1.
PTAL @coocood @winoros