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Updated default of tidb_stmt_summary_max_sql_length from 4k to 32k #21867

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Updated default of tidb_stmt_summary_max_sql_length from 4k to 32k #21867

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4 changes: 2 additions & 2 deletions sql-statements/sql-statement-show-variables.md
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Expand Up @@ -124,7 +124,7 @@ mysql> SHOW GLOBAL VARIABLES LIKE 'tidb%';
| tidb_snapshot | |
| tidb_stmt_summary_history_size | 24 |
| tidb_stmt_summary_internal_query | 0 |
| tidb_stmt_summary_max_sql_length | 4096 |
| tidb_stmt_summary_max_sql_length | 32768 |
| tidb_stmt_summary_max_stmt_count | 3000 |
| tidb_stmt_summary_refresh_interval | 1800 |
| tidb_store_limit | 0 |
Expand Down Expand Up @@ -173,4 +173,4 @@ The `SHOW [GLOBAL|SESSION] VARIABLES` statement in TiDB is fully compatible with

## See also

* [`SET [GLOBAL|SESSION]`](/sql-statements/sql-statement-set-variable.md)
* [`SET [GLOBAL|SESSION]`](/sql-statements/sql-statement-set-variable.md)
2 changes: 1 addition & 1 deletion statement-summary-tables.md
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Expand Up @@ -143,7 +143,7 @@ The following system variables are used to control the statement summary:
> - When a SQL digest is evicted, its related summary data of all time ranges is removed from both the `statements_summary` and `statements_summary_history` tables. As a result, even if the number of SQL digests within a specific time range does not exceed the limit, the number of SQL digests in the `statements_summary_history` table might be less than the actual number of SQL digests. If this situation occurs and affects performance, you are recommended to increase the value of `tidb_stmt_summary_max_stmt_count`.
> - For TiDB Self-Managed, when [`tidb_stmt_summary_enable_persistent`](#persist-statements-summary) is enabled, data in the `statements_summary_history` table is persisted to the disk. In this case, `tidb_stmt_summary_max_stmt_count` only limits the number of SQL digests that the `statements_summary` table can store in memory, and TiDB evicts the least recently used SQL digests only from the `statements_summary` table when `tidb_stmt_summary_max_stmt_count` is exceeded.

- `tidb_stmt_summary_max_sql_length`: Specifies the longest display length of `DIGEST_TEXT` and `QUERY_SAMPLE_TEXT`. The default value is `4096`.
- `tidb_stmt_summary_max_sql_length`: Specifies the longest display length of `DIGEST_TEXT` and `QUERY_SAMPLE_TEXT`. The default value is `32768`.
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low

For better readability and consistency, it's helpful to add the human-readable unit (KiB) next to the byte value. This aligns with the documentation style for other byte-sized variables.

Suggested change
- `tidb_stmt_summary_max_sql_length`: Specifies the longest display length of `DIGEST_TEXT` and `QUERY_SAMPLE_TEXT`. The default value is `32768`.
- `tidb_stmt_summary_max_sql_length`: Specifies the longest display length of `DIGEST_TEXT` and `QUERY_SAMPLE_TEXT`. The default value is `32768` (32 KiB).

- `tidb_stmt_summary_internal_query`: Determines whether to count the TiDB SQL statements. `1` means to count, and `0` means not to count. The default value is `0`.

An example of the statement summary configuration is shown as follows:
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2 changes: 1 addition & 1 deletion system-variables.md
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Expand Up @@ -6007,7 +6007,7 @@ For details, see [Identify Slow Queries](/identify-slow-queries.md).
- Persists to cluster: Yes
- Applies to hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value): No
- Type: Integer
- Default value: `4096`
- Default value: `32768`
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low

For better readability and consistency with how other byte-sized variables are documented in this file (e.g., tidb_query_log_max_len), it's helpful to add the human-readable unit (KiB) next to the byte value.

Suggested change
- Default value: `32768`
- Default value: `32768` (32 KiB)

- Range: `[0, 2147483647]`
- Unit: Bytes

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