feat: Use NDV for equality filter selectivity calculation#20789
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alamb merged 8 commits intoapache:mainfrom Apr 3, 2026
Merged
feat: Use NDV for equality filter selectivity calculation#20789alamb merged 8 commits intoapache:mainfrom
alamb merged 8 commits intoapache:mainfrom
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kosiew
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Mar 20, 2026
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@jonathanc-n
Thanks for the working on this.
I do think there’s one correctness issue in the new singleton-selectivity branch that should be addressed before merge, and I left one small follow-up suggestion that could make the logic easier to read.
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run benchmarks |
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No perf changes should occur here, either this or #21077 would need to be merged before we can test performance |
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) ## Which issue does this PR close? - Part of #20766 Related: #20789 (uses NDV for equality filter selectivity, complementary - this PR improves the NDV output stats, that PR consumes them) ## Rationale for this change When a filter predicate collapses a column interval to a single value (e.g. `d_qoy = 1`), the output column can only have one distinct value. Currently `distinct_count` is always demoted to `Inexact`, losing this information. This matters for downstream optimizers that rely on `distinct_count`, such as join cardinality estimation in `estimate_inner_join_cardinality`. ## What changes are included in this PR? In `collect_new_statistics` (filter.rs), when the post-filter interval has `lower == upper` (both non-null), set `distinct_count` to `Precision::Exact(1)` instead of demoting the input NDV to `Inexact`. ## Are these changes tested? Yes, 4 unit tests: - Equality predicate (`a = 42`) -> NDV becomes `Exact(1)` - OR predicate (`a = 42 OR a = 22`) -> interval does not collapse, NDV stays `Inexact` - AND with mixed predicates (`a = 42 AND b > 10 AND c = 7`) -> `a` and `c` get `Exact(1)`, `b` stays `Inexact` - Equality with absent bounds (`a = 42`, no min/max) -> interval analysis still resolves to `Exact(1)` ## Are there any user-facing changes? No breaking changes. Statistics consumers will now see `Exact(1)` for `distinct_count` on columns constrained to a single value by filter predicates. Disclaimer: I used AI to assist in the code generation, I have manually reviewed the output and it matches my intention and understanding. --------- Co-authored-by: xudong.w <wxd963996380@gmail.com>
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…che#21077) ## Which issue does this PR close? - Part of apache#20766 Related: apache#20789 (uses NDV for equality filter selectivity, complementary - this PR improves the NDV output stats, that PR consumes them) ## Rationale for this change When a filter predicate collapses a column interval to a single value (e.g. `d_qoy = 1`), the output column can only have one distinct value. Currently `distinct_count` is always demoted to `Inexact`, losing this information. This matters for downstream optimizers that rely on `distinct_count`, such as join cardinality estimation in `estimate_inner_join_cardinality`. ## What changes are included in this PR? In `collect_new_statistics` (filter.rs), when the post-filter interval has `lower == upper` (both non-null), set `distinct_count` to `Precision::Exact(1)` instead of demoting the input NDV to `Inexact`. ## Are these changes tested? Yes, 4 unit tests: - Equality predicate (`a = 42`) -> NDV becomes `Exact(1)` - OR predicate (`a = 42 OR a = 22`) -> interval does not collapse, NDV stays `Inexact` - AND with mixed predicates (`a = 42 AND b > 10 AND c = 7`) -> `a` and `c` get `Exact(1)`, `b` stays `Inexact` - Equality with absent bounds (`a = 42`, no min/max) -> interval analysis still resolves to `Exact(1)` ## Are there any user-facing changes? No breaking changes. Statistics consumers will now see `Exact(1)` for `distinct_count` on columns constrained to a single value by filter predicates. Disclaimer: I used AI to assist in the code generation, I have manually reviewed the output and it matches my intention and understanding. --------- Co-authored-by: xudong.w <wxd963996380@gmail.com>
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Apr 21, 2026
## Which issue does this PR close? <!-- We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example `Closes apache#123` indicates that this PR will close issue apache#123. --> - Part of apache#20766 . ## Rationale for this change Used NDV for equality filter selectivity calculation. <!-- Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed. Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes. --> ## What changes are included in this PR? Check if it is equality filter, and selectivity will be calculated using (1/NDV) <!-- There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR. --> ## Are these changes tested? <!-- We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 2. Serve as another way to document the expected behavior of the code If tests are not included in your PR, please explain why (for example, are they covered by existing tests)? --> ## Are there any user-facing changes? <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. --> <!-- If there are any breaking changes to public APIs, please add the `api change` label. --> --------- Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>
Rich-T-kid
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Apr 21, 2026
…che#21077) ## Which issue does this PR close? - Part of apache#20766 Related: apache#20789 (uses NDV for equality filter selectivity, complementary - this PR improves the NDV output stats, that PR consumes them) ## Rationale for this change When a filter predicate collapses a column interval to a single value (e.g. `d_qoy = 1`), the output column can only have one distinct value. Currently `distinct_count` is always demoted to `Inexact`, losing this information. This matters for downstream optimizers that rely on `distinct_count`, such as join cardinality estimation in `estimate_inner_join_cardinality`. ## What changes are included in this PR? In `collect_new_statistics` (filter.rs), when the post-filter interval has `lower == upper` (both non-null), set `distinct_count` to `Precision::Exact(1)` instead of demoting the input NDV to `Inexact`. ## Are these changes tested? Yes, 4 unit tests: - Equality predicate (`a = 42`) -> NDV becomes `Exact(1)` - OR predicate (`a = 42 OR a = 22`) -> interval does not collapse, NDV stays `Inexact` - AND with mixed predicates (`a = 42 AND b > 10 AND c = 7`) -> `a` and `c` get `Exact(1)`, `b` stays `Inexact` - Equality with absent bounds (`a = 42`, no min/max) -> interval analysis still resolves to `Exact(1)` ## Are there any user-facing changes? No breaking changes. Statistics consumers will now see `Exact(1)` for `distinct_count` on columns constrained to a single value by filter predicates. Disclaimer: I used AI to assist in the code generation, I have manually reviewed the output and it matches my intention and understanding. --------- Co-authored-by: xudong.w <wxd963996380@gmail.com>
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Which issue does this PR close?
Rationale for this change
Used NDV for equality filter selectivity calculation.
What changes are included in this PR?
Check if it is equality filter, and selectivity will be calculated using (1/NDV)
Are these changes tested?
Are there any user-facing changes?