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sql: add optimizer_use_max_frequency_selectivity session setting
The `optimizer_use_max_frequency_selectivity` session setting has been added. It is enabled by default. Disabling it reverts the selectivity improvements added in #151409. Release note: None
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‎pkg/sql/logictest/testdata/logic_test/information_schema‎

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@@ -4217,6 +4217,7 @@ optimizer_use_improved_zigzag_join_costing on
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optimizer_use_limit_ordering_for_streaming_group_by on
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optimizer_use_lock_elision_multiple_families off
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optimizer_use_lock_op_for_serializable off
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optimizer_use_max_frequency_selectivity on
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optimizer_use_merged_partial_statistics on
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optimizer_use_multicol_stats on
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optimizer_use_not_visible_indexes off

‎pkg/sql/logictest/testdata/logic_test/pg_catalog‎

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@@ -3166,6 +3166,7 @@ optimizer_use_improved_zigzag_join_costing on
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optimizer_use_limit_ordering_for_streaming_group_by on NULL NULL NULL string
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optimizer_use_lock_elision_multiple_families off NULL NULL NULL string
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optimizer_use_lock_op_for_serializable off NULL NULL NULL string
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optimizer_use_max_frequency_selectivity on NULL NULL NULL string
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optimizer_use_merged_partial_statistics on NULL NULL NULL string
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optimizer_use_multicol_stats on NULL NULL NULL string
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optimizer_use_not_visible_indexes off NULL NULL NULL string
@@ -3412,6 +3413,7 @@ optimizer_use_improved_zigzag_join_costing on
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optimizer_use_limit_ordering_for_streaming_group_by on NULL user NULL on on
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optimizer_use_lock_elision_multiple_families off NULL user NULL off off
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optimizer_use_lock_op_for_serializable off NULL user NULL off off
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optimizer_use_max_frequency_selectivity on NULL user NULL on on
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optimizer_use_merged_partial_statistics on NULL user NULL on on
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optimizer_use_multicol_stats on NULL user NULL on on
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optimizer_use_not_visible_indexes off NULL user NULL off off
@@ -3649,6 +3651,7 @@ optimizer_use_improved_zigzag_join_costing NULL NULL
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optimizer_use_limit_ordering_for_streaming_group_by NULL NULL NULL NULL NULL
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optimizer_use_lock_elision_multiple_families NULL NULL NULL NULL NULL
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optimizer_use_lock_op_for_serializable NULL NULL NULL NULL NULL
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optimizer_use_max_frequency_selectivity NULL NULL NULL NULL NULL
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optimizer_use_merged_partial_statistics NULL NULL NULL NULL NULL
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optimizer_use_multicol_stats NULL NULL NULL NULL NULL
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optimizer_use_not_visible_indexes NULL NULL NULL NULL NULL

‎pkg/sql/logictest/testdata/logic_test/show_source‎

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@@ -183,6 +183,7 @@ optimizer_use_improved_zigzag_join_costing on
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optimizer_use_limit_ordering_for_streaming_group_by on
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optimizer_use_lock_elision_multiple_families off
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optimizer_use_lock_op_for_serializable off
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optimizer_use_max_frequency_selectivity on
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optimizer_use_merged_partial_statistics on
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optimizer_use_multicol_stats on
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optimizer_use_not_visible_indexes off

‎pkg/sql/opt/memo/memo.go‎

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@@ -214,6 +214,7 @@ type Memo struct {
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rowSecurity bool
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clampLowHistogramSelectivity bool
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clampInequalitySelectivity bool
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useMaxFrequencySelectivity bool
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// txnIsoLevel is the isolation level under which the plan was created. This
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// affects the planning of some locking operations, so it must be included in
@@ -328,6 +329,7 @@ func (m *Memo) Init(ctx context.Context, evalCtx *eval.Context) {
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rowSecurity: evalCtx.SessionData().RowSecurity,
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clampLowHistogramSelectivity: evalCtx.SessionData().OptimizerClampLowHistogramSelectivity,
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clampInequalitySelectivity: evalCtx.SessionData().OptimizerClampInequalitySelectivity,
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useMaxFrequencySelectivity: evalCtx.SessionData().OptimizerUseMaxFrequencySelectivity,
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txnIsoLevel: evalCtx.TxnIsoLevel,
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}
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m.metadata.Init()
@@ -506,6 +508,7 @@ func (m *Memo) IsStale(
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m.rowSecurity != evalCtx.SessionData().RowSecurity ||
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m.clampLowHistogramSelectivity != evalCtx.SessionData().OptimizerClampLowHistogramSelectivity ||
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m.clampInequalitySelectivity != evalCtx.SessionData().OptimizerClampInequalitySelectivity ||
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m.useMaxFrequencySelectivity != evalCtx.SessionData().OptimizerUseMaxFrequencySelectivity ||
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m.txnIsoLevel != evalCtx.TxnIsoLevel {
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return true, nil
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}

‎pkg/sql/opt/memo/memo_test.go‎

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@@ -510,6 +510,12 @@ func TestMemoIsStale(t *testing.T) {
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evalCtx.SessionData().OptimizerUseImprovedMultiColumnSelectivityEstimate = false
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notStale()
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// Stale optimizer_use_max_frequency_selectivity.
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evalCtx.SessionData().OptimizerUseMaxFrequencySelectivity = true
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stale()
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evalCtx.SessionData().OptimizerUseMaxFrequencySelectivity = false
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notStale()
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// Stale optimizer_prove_implication_with_virtual_computed_columns.
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evalCtx.SessionData().OptimizerProveImplicationWithVirtualComputedColumns = true
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stale()

‎pkg/sql/opt/memo/statistics_builder.go‎

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@@ -4670,6 +4670,9 @@ func (sb *statisticsBuilder) selectivityFromMaxFrequencies(
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) (selectivity, selectivityUpperBound props.Selectivity, maxFreqCols opt.ColSet) {
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selectivity = props.OneSelectivity
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selectivityUpperBound = props.OneSelectivity
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if !sb.evalCtx.SessionData().OptimizerUseMaxFrequencySelectivity {
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return selectivity, selectivityUpperBound, opt.ColSet{}
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}
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for col, ok := cols.Next(0); ok; col, ok = cols.Next(col + 1) {
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c := opt.MakeColSet(col)
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inputColStat, inputStats := sb.colStatFromInput(c, e)

‎pkg/sql/opt/memo/testdata/stats/generic‎

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@@ -254,6 +254,27 @@ select
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└── filters
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└── i:2 = $1 [type=bool, outer=(2), constraints=(/2: (/NULL - ]), fd=()-->(2)]
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257+
# Fallback to ~row_count/distinct_count if
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# optimizer_use_max_frequency_selectivity is false.
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norm set=(optimizer_use_max_frequency_selectivity=false)
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SELECT * FROM t WHERE i = $1
261+
----
262+
select
263+
├── columns: k:1(int!null) i:2(int!null) s:3(string)
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├── has-placeholder
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├── stats: [rows=24.25, distinct(2)=1, null(2)=0]
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├── key: (1)
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├── fd: ()-->(2), (1)-->(3)
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├── scan t
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│ ├── columns: k:1(int!null) i:2(int) s:3(string)
270+
│ ├── stats: [rows=1000, distinct(1)=1000, null(1)=0, distinct(2)=41, null(2)=30]
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│ │ histogram(2)= 0 30 0 0 90 10 180 10 270 20 360 30
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│ │ <--- NULL --- 0 ---- 100 ----- 200 ----- 300 ----- 400
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│ ├── key: (1)
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│ └── fd: (1)-->(2,3)
275+
└── filters
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└── i:2 = $1 [type=bool, outer=(2), constraints=(/2: (/NULL - ]), fd=()-->(2)]
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# Similar case as above, but with opt to ensure the correct row counts are used
258279
# for new memo groups.
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opt

‎pkg/sql/sessiondatapb/local_only_session_data.proto‎

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@@ -749,6 +749,9 @@ message LocalOnlySessionData {
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// clamp the selectivity of open-ended inequality filters (e.g. <, >, !=)
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// but not (=, BETWEEN etc.) to a minimum threshold.
751751
bool optimizer_clamp_inequality_selectivity = 190;
752+
// OptimizerUseMaxFrequencySelectivity, when true, indicates that the
753+
// optimizer should use max frequency for selectivity estimation.
754+
bool optimizer_use_max_frequency_selectivity = 191;
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///////////////////////////////////////////////////////////////////////////
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// WARNING: consider whether a session parameter you're adding needs to //

‎pkg/sql/sessionmutator/mutator.go‎

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@@ -1098,3 +1098,7 @@ func (m *SessionDataMutator) SetOptimizerClampLowHistogramSelectivity(val bool)
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func (m *SessionDataMutator) SetOptimizerClampInequalitySelectivity(val bool) {
10991099
m.Data.OptimizerClampInequalitySelectivity = val
11001100
}
1101+
1102+
func (m *SessionDataMutator) SetOptimizerUseMaxFrequencySelectivity(val bool) {
1103+
m.Data.OptimizerUseMaxFrequencySelectivity = val
1104+
}

‎pkg/sql/vars.go‎

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@@ -3729,6 +3729,23 @@ var varGen = map[string]sessionVar{
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GlobalDefault: globalTrue,
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},
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// CockroachDB extension.
3733+
`optimizer_use_max_frequency_selectivity`: {
3734+
GetStringVal: makePostgresBoolGetStringValFn(`optimizer_use_max_frequency_selectivity`),
3735+
Set: func(_ context.Context, m sessionmutator.SessionDataMutator, s string) error {
3736+
b, err := paramparse.ParseBoolVar("optimizer_use_max_frequency_selectivity", s)
3737+
if err != nil {
3738+
return err
3739+
}
3740+
m.SetOptimizerUseMaxFrequencySelectivity(b)
3741+
return nil
3742+
},
3743+
Get: func(evalCtx *extendedEvalContext, _ *kv.Txn) (string, error) {
3744+
return formatBoolAsPostgresSetting(evalCtx.SessionData().OptimizerUseMaxFrequencySelectivity), nil
3745+
},
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GlobalDefault: globalTrue,
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},
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// CockroachDB extension.
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`optimizer_prove_implication_with_virtual_computed_columns`: {
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GetStringVal: makePostgresBoolGetStringValFn(`optimizer_prove_implication_with_virtual_computed_columns`),

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