Fix explain indexes with use_skip_indexes_on_data_read + use_query_condition_cache#88504
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shankar-iyer merged 18 commits intoClickHouse:masterfrom Oct 31, 2025
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Workflow [PR], commit [d3a0ede] Summary: ❌
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| const bool use_skip_indexes_on_data_read = settings[Setting::use_skip_indexes_on_data_read] && !is_parallel_reading_from_replicas; | ||
| const bool use_skip_indexes_on_data_read = settings[Setting::use_skip_indexes_on_data_read] && !is_parallel_reading_from_replicas && |
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Safe use of skip indexes in FINAL queries with use_skip_indexes_if_final_exact_mode=1 requires an additional PrimaryKeyExpand step and that step has to be done during full index analysis and cannot be postponed to data read time.
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For Reference : 4 issues were found when testing this PR
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| if (is_parallel_reading_from_replicas) | ||
| return false; | ||
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| if (settings[Setting::read_overflow_mode] == OverflowMode::THROW && settings[Setting::max_rows_to_read]) /// Need to do full index analysis to get row count estimate |
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This deserves a longer comment.
Maybe:
/// Settings `read_overflow_mode = 'throw'` and `max_rows_to_read` are evaluated early during execution, during initialization of the pipeline based on estimated row counts. Estimation doesn't work properly if the skip index is evaluated during data read (scan).| if (is_final_query && settings[Setting::use_skip_indexes_if_final_exact_mode]) | ||
| return false; | ||
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| if (settings[Setting::read_overflow_mode] == OverflowMode::THROW && settings[Setting::max_rows_to_read]) /// Need to do full index analysis to get row count estimate |
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Needs a similarly long comment as above, see my proposal in the other comment.
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…n_data_read + use_query_condition_cache
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Backport #88504 to 25.10: Fix explain indexes with use_skip_indexes_on_data_read + use_query_condition_cache
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Fixes explain indexes with use_skip_indexes_on_data_read + use_query_condition_cache. Behavior change introduced and fixed in 25.10.
Resolves #88467