releases: add the change of "max_execution_time" (#18695)

pingcap · Aug 29, 2024 · c2af846 · c2af846
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diff --git a/releases/release-6.4.0.md b/releases/release-6.4.0.md
@@ -278,6 +278,7 @@ In v6.4.0-DMR, the key new features and improvements are as follows:
 
 | Variable name | Change type | Description |
 |--------|------------------------------|------|
+| [`max_execution_time`](/system-variables.md#max_execution_time) | Modified | Before v6.4.0, this variable takes effect on all types of statements. Starting from v6.4.0, this variable only controls the maximum execution time of read-only statements. |
 | [`tidb_constraint_check_in_place_pessimistic`](/system-variables.md#tidb_constraint_check_in_place_pessimistic-new-in-v630) | Modified | Removes the GLOBAL scope and allows you to modify the default value using the [`pessimistic-txn.constraint-check-in-place-pessimistic`](/tidb-configuration-file.md#constraint-check-in-place-pessimistic-new-in-v640) configuration item. This variable controls when TiDB checks the unique constraints in pessimistic transactions. |
 | [`tidb_ddl_flashback_concurrency`](/system-variables.md#tidb_ddl_flashback_concurrency-new-in-v630) | Modified | Takes effect starting from v6.4.0 and controls the concurrency of [`FLASHBACK CLUSTER TO TIMESTAMP`](/sql-statements/sql-statement-flashback-cluster.md). The default value is `64`. |
 | [`tidb_enable_clustered_index`](/system-variables.md#tidb_enable_clustered_index-new-in-v50) | Modified | Changes the default value from `INT_ONLY` to `ON`, meaning that primary keys are created as clustered indexes by default.|

diff --git a/system-variables.md b/system-variables.md
@@ -737,7 +737,7 @@ This variable is an alias for [`last_insert_id`](#last_insert_id).
 
 > **Note:**
 >
-> The `max_execution_time` system variable currently only controls the maximum execution time for read-only SQL statements. The precision of the timeout value is roughly 100ms. This means the statement might not be terminated in accurate milliseconds as you specify.
+> Before v6.4.0, the `max_execution_time` system variable takes effect on all types of statements. Starting from v6.4.0, this variable only controls the maximum execution time of read-only statements. The precision of the timeout value is roughly 100ms. This means the statement might not be terminated in exact milliseconds as you specify.
 
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