HIVE-29740 : Fix SHOW TABLES operation taking 300 seconds+ on very large databases#6610
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@deniskuzZ / @ayushtkn / @dengzhhu653 / @zabetak / @saihemanth-cloudera Can you help to review this PR? Thanks. |
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| * separate-thread execution, which breaks Mockito's ThreadLocal-based MockedStatic. | ||
| */ | ||
| @Test | ||
| public void testFilterTables_performance_100kTables() throws Exception { |
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nit: a hard 5s wall-clock assert can be unstable on slow/shared runners. Consider adding @Category(SlowTests.class)
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Will handle it as a part of a follow up JIRA if that's okay since it is a reasonable scope for a separate JIRA itself?
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What changes were proposed in this pull request?
This PR optimizes AuthorizationMetaStoreFilterHook.filterTables() by replacing the existing O(n²) nested-loop cartesian-product implementation with a sort + binary search filtering.
Why are the changes needed?
On very large databases, SHOW TABLES can become extremely slow because filterTables() performs a nested search between the authorized objects and the table list.
With 100,000 tables, the previous implementation performs on the order of 10 billion comparisons, causing execution times of 200–300 seconds.
The new implementation reduces the lookup complexity while preserving the existing authorization semantics, reducing execution time to well under 5 seconds in the included performance test.
Does this PR introduce any user-facing change?
Users running commands such as SHOW TABLES on very large databases should observe a significant reduction in execution time. There are no functional or behavioral changes to authorization or query results; only the performance of table filtering is improved.
How was this patch tested?
Tested with 100,000 tables