Un-flake 01079_new_range_reader_segfault #48934
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Usage of `rand()` means that the SELECT produces with probability 0.5^20 = 0.000000953 no result. This happend in (*). The query is build to trigger some specific logic in MergeTreeReader. Rewriting it is not a good idea. I therefore increased the amout of test data to reduce the probability of en empty result siginficantly. I hope that the same logic as before is triggered. (*) https://s3.amazonaws.com/clickhouse-test-reports/0/905587b39def432667437efd92c28dde9cc0dfb2/stateless_tests__release__s3_storage__[1/2].html
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rschu1ze
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nickitat
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Apr 19, 2023
| @@ -3,7 +3,7 @@ drop table if exists t; | |||
| create table t (a Int) engine = MergeTree order by a; | |||
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| -- some magic to satisfy conditions to run optimizations in MergeTreeRangeReader | |||
| insert into t select number < 20 ? 0 : 1 from numbers(50); | |||
| insert into t select number < 20000 ? 0 : 1 from numbers(50000); | |||
| alter table t add column s String default 'foo'; | |||
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| select s from t prewhere a != 1 where rand() % 2 = 0 limit 1; | |||
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maybe modify condition in to smth determenistic like where rowNumberInBlock() % 2 = 0?
nickitat
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Apr 19, 2023
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Usage of
rand()means that the SELECT produces with probability 0.5^20 = 0.000000953 no result. This happend in (*).The query is designed to trigger some specific logic in MergeTreeReader. Rewriting it is not a good idea. I therefore increased the amount of test data to reduce the probability of an empty result significantly. I hope that the same logic as before is triggered.
EDIT: Instead replaced
rand()by the more deterministicrowNumberInBlock().The test currently runs 507 times / day, this means this PR will prevent a failure in ca. 5.6 years from now. Happy 2028!
(*) https://s3.amazonaws.com/clickhouse-test-reports/0/905587b39def432667437efd92c28dde9cc0dfb2/stateless_tests__release__s3_storage__[1/2].html
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