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Update TiDB configuration max-index-length (#21751) #21757

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Sep 11, 2025
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Update TiDB configuration max-index-length (#21751) #21757

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Update TiDB configuration max-index-length
Frank945946 Sep 11, 2025
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Frank945946 Sep 11, 2025
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qiancai Sep 11, 2025
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Update tidb-configuration-file.md
qiancai Sep 11, 2025
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8 changes: 7 additions & 1 deletion tidb-configuration-file.md
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Expand Up @@ -156,7 +156,13 @@ The TiDB configuration file supports more options than command-line parameters.
- Sets the maximum allowable length of the newly created index.
- Default value: `3072`
- Unit: byte
- Currently, the valid value range is `[3072, 3072*4]`. MySQL and TiDB (version < v3.0.11) do not have this configuration item, but both limit the length of the newly created index. This limit in MySQL is `3072`. In TiDB (version =< 3.0.7), this limit is `3072*4`. In TiDB (3.0.7 < version < 3.0.11), this limit is `3072`. This configuration is added to be compatible with MySQL and earlier versions of TiDB.
- Range: `[3072, 3072*4]`
- Compatibility:
- MySQL: the maximum index length is fixed at 3072 bytes.
- Earlier versions of TiDB:
- v3.0.7 and earlier: the maximum index length is fixed at 3072 × 4 bytes.
- v3.0.8 ~ v3.0.10: the maximum index length is fixed at 3072 bytes.
- v3.0.11 and later versions: TiDB introduces the `max-index-length` configuration item to ensure compatibility with different TiDB versions and with MySQL.

### `table-column-count-limit` <span class="version-mark">New in v5.0</span>

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