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sys-variables: update tidb_schema_cache_size default value #19007

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sys-variables: update tidb_schema_cache_size default value #19007

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sys-variables: update @@tidb_schema_cache_size default value
tiancaiamao Sep 26, 2024
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Update system-variables.md
tiancaiamao Sep 26, 2024
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hfxsd Oct 9, 2024
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hfxsd Oct 9, 2024
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lilin90 Oct 9, 2024
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10 changes: 6 additions & 4 deletions system-variables.md
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Expand Up @@ -5163,15 +5163,17 @@ SHOW WARNINGS;

> **Warning:**
>
> The feature controlled by this variable is not yet effective in the current TiDB version. Do not change the default value.
> The feature controlled by this variable is experimental. It is not recommended that you use it in the production environment. This feature might be changed or removed without prior notice. If you find a bug, you can report an [issue](https://github.com/pingcap/tidb/issues) on GitHub.

- Scope: GLOBAL
- Persists to cluster: Yes
- Applies to hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value): No
- Type: Integer
- Default value: `0`
- Range: `0` or `[536870912, 9223372036854775807]`
- This variable controls the size of the schema cache in TiDB. The unit is byte. The default value is `0`, which means the cache limit feature is disabled. To enable this feature, you need to set a value within the range `[536870912, 9223372036854775807]`. TiDB will use this value as the maximum available memory limit and apply the Least Recently Used (LRU) algorithm to cache the required tables, effectively reducing the memory used by schema information.
- Default value: `536870912` (512 MiB)
- Range: `0` or `[67108864, 9223372036854775807]`
- Before TiDB v8.4.0, the default value of this variable is `0`.
- Starting from TiDB v8.4.0, the default value is `536870912`. When you upgrade from an earlier version to v8.4.0 or later, the old values will still be used.
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- This variable controls the size of the schema cache in TiDB. The unit is byte. If the value is `0`, it means the cache limit feature is disabled. To enable this feature, you need to set a value within the range `[67108864, 9223372036854775807]`. TiDB will use this value as the maximum available memory limit and apply the Least Recently Used (LRU) algorithm to cache the required tables, effectively reducing the memory used by schema information.
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### tidb_schema_version_cache_limit <span class="version-mark">New in v7.4.0</span>

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