Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Updated the Schema Cache limitations #19374

Merged
merged 6 commits into from
Nov 12, 2024
Merged

Updated the Schema Cache limitations #19374

Changes from all commits
Commits
Show all changes
6 commits
Select commit Hold shift + click to select a range
1bd785e
Update schema-cache.md
Frank945946 Nov 12, 2024
c74d36d
Update schema-cache.md
hfxsd Nov 12, 2024
1da0a38
Update schema-cache.md
hfxsd Nov 12, 2024
f4a732f
Update schema-cache.md
hfxsd Nov 12, 2024
a5de7ce
Update schema-cache.md
hfxsd Nov 12, 2024
12ef872
Update schema-cache.md
hfxsd Nov 12, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions schema-cache.md
View file
Open in desktop
Original file line number Diff line number Diff line change
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 the [`AUTO_INCREMENT`](/auto-increment.md) or [`AUTO_RANDOM`](/auto-random.md) attribute, a small schema cache size might cause these tables to frequently enter and leave the cache. You can monitor it 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, it is recommended to take the following measures:
Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Suggested change
- When you use tables with the [`AUTO_INCREMENT`](/auto-increment.md) or [`AUTO_RANDOM`](/auto-random.md) attribute, a small schema cache size might cause these tables to frequently enter and leave the cache. You can monitor it 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, it is recommended to take the following measures:
- When you use tables with the [`AUTO_INCREMENT`](/auto-increment.md) or [`AUTO_RANDOM`](/auto-random.md) attribute, a small schema cache size might cause the meta data of these tables to frequently enter and leave the cache. 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, it is recommended to take the following measures:

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

a small schema cache size might cause the metadata of these tables to be frequently cached and evicted in memory.


- Increase the schema cache size to reduce frequent evictions.
Copy link
Collaborator

@hfxsd hfxsd Nov 12, 2024 •
edited
Loading

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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 shard bits and reserved bits of `AUTO_RANDOM` to avoid a too small ID range.
Loading