doc: add design doc for stats lru cache #36804
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Signed-off-by: yisaer <[email protected]>
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Code Coverage Details: https://codecov.io/github/pingcap/tidb/commit/ed0aed4c6679833a87b0327e252a0b2b17f3e0dd |
| ### Sync Stats Compatibility | ||
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| Previously tidb server has Sync Stats and asynchronously Loading Histograms in order to load column stats into memory during query. | ||
| As Stats LRU Cache Policy may evict index stats in memory, we also need Sync Stats and asynchronously Loading Histograms to support loading index stats according to its loading status to keep compatible. |
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Do we need more details to tell when the load will be triggered after eviction?
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LGTM for this part, while Sync Stats doesn't have design doc in this repo yet...
| ### Goal | ||
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| - Use LRU to maintain the stats cache in memory | ||
| - Keep the total memory usage of stats cache under the quota |
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The third one, provide a way to efficiently load evicted stats back into cache once needed?
| ### Stats Cache Interface | ||
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| We will provide a Stats Cache Interface which is implemented by LRU Cache and Map Cache. | ||
| If the tidb server didn't enable Stats LRU Cache, it will use Map Cache by default. |
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What about introducing the variables to turn on LRU and to set the capacity?
Signed-off-by: yisaer <[email protected]>
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This pull request has been accepted and is ready to merge. Commit hash: a3c4cf0
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Signed-off-by: yisaer [email protected]
What problem does this PR solve?
Issue Number: ref #34052
Problem Summary:
What is changed and how it works?
add design doc for stats lru cache
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Tests
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