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Updated the Schema Cache limitations #19374

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Nov 12, 2024
Merged

Updated the Schema Cache limitations #19374

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hfxsd Nov 12, 2024
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5 changes: 5 additions & 0 deletions schema-cache.md
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Expand Up @@ -36,3 +36,8 @@ In scenarios with a large number of databases and tables, the following known is
- `SHOW FULL TABLES`
- `FLASHBACK`
- `ALTER TABLE ... SET TIFLASH MODE ...`
- When you use tables with `AUTO_INCREMENT` or `AUTO_RANDOM`, a small schema cache size might cause these tables to frequently enter and leave the cache, which can be monitored through the schema cache hit rate and size on the monitoring panel. This can result in the allocated ID range becoming invalid before being fully used, leading to ID jumps. In write-intensive scenarios, this might even exhaust the ID range. To minimize abnormal ID allocation behavior and improve system stability, consider the following measures:
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- Increase the schema cache size to reduce frequent evictions.
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@hfxsd hfxsd Nov 12, 2024 •
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Suggested change
- Increase the schema cache size to reduce frequent evictions.
- View the hit rate and size of the schema cache on the monitoring panel to assess whether the cache settings are reasonable. Increase the schema cache size properly to reduce frequent evictions.

- Set [`AUTO_ID_CACHE`](/auto-increment.md#auto_id_cache) to `1` to prevent ID jumps.
- Properly configure the sharding bits and reserved bits for AUTO_RANDOM to avoid having a limited ID range.
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