From 258c3bf173b69f2d3b12cbe5f0b198ebbb2b4d7e Mon Sep 17 00:00:00 2001 From: Jianjun Liao Date: Thu, 31 Jul 2025 13:50:28 +0800 Subject: [PATCH 1/6] draft Signed-off-by: Jianjun Liao --- system-variables.md | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/system-variables.md b/system-variables.md index 2c3b95d31d929..002d973e8cda8 100644 --- a/system-variables.md +++ b/system-variables.md @@ -1012,6 +1012,16 @@ mysql> SHOW GLOBAL VARIABLES LIKE 'max_prepared_stmt_count'; - Unit: Bytes - This variable is used to control the threshold at which the TiDB server prefers to send read requests to a replica in the same availability zone as the TiDB server when [`tidb_replica_read`](#tidb_replica_read-new-in-v40) is set to `closest-adaptive`. If the estimated result is higher than or equal to this threshold, TiDB prefers to send read requests to a replica in the same availability zone. Otherwise, TiDB sends read requests to the leader replica. +### tidb_advancer_check_point_lag_limit New in v9.1.0 + +- Scope: GLOBAL +- Persists to cluster: Yes +- Applies to hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value): No +- Type: Duration +- Default value: `48h0m0s` +- Range: `[1s, 8760h0m0s]` +- This variable is used to control the lag time limit of the log backup task checkpoint. If the checkpoint lag of the log backup task exceeds this limit, the task will be paused by TiDB Advancer. + ### tidb_allow_tiflash_cop New in v7.3.0 - Scope: SESSION | GLOBAL From 6bf19b575e7ccfe1a15e88dc753e9ae285831387 Mon Sep 17 00:00:00 2001 From: Jianjun Liao <36503113+Leavrth@users.noreply.github.com> Date: Tue, 5 Aug 2025 11:35:56 +0800 Subject: [PATCH 2/6] Update system-variables.md --- system-variables.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/system-variables.md b/system-variables.md index 002d973e8cda8..1714c6ac4647a 100644 --- a/system-variables.md +++ b/system-variables.md @@ -1012,7 +1012,7 @@ mysql> SHOW GLOBAL VARIABLES LIKE 'max_prepared_stmt_count'; - Unit: Bytes - This variable is used to control the threshold at which the TiDB server prefers to send read requests to a replica in the same availability zone as the TiDB server when [`tidb_replica_read`](#tidb_replica_read-new-in-v40) is set to `closest-adaptive`. If the estimated result is higher than or equal to this threshold, TiDB prefers to send read requests to a replica in the same availability zone. Otherwise, TiDB sends read requests to the leader replica. -### tidb_advancer_check_point_lag_limit New in v9.1.0 +### tidb_advancer_check_point_lag_limit New in v9.0.0 - Scope: GLOBAL - Persists to cluster: Yes From 1e00141a727b228dcb3ce21b10097d1d9f651e4f Mon Sep 17 00:00:00 2001 From: xixirangrang Date: Tue, 5 Aug 2025 12:06:13 +0800 Subject: [PATCH 3/6] Update system-variables.md Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com> --- system-variables.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/system-variables.md b/system-variables.md index 1714c6ac4647a..909458c7072b0 100644 --- a/system-variables.md +++ b/system-variables.md @@ -1020,7 +1020,7 @@ mysql> SHOW GLOBAL VARIABLES LIKE 'max_prepared_stmt_count'; - Type: Duration - Default value: `48h0m0s` - Range: `[1s, 8760h0m0s]` -- This variable is used to control the lag time limit of the log backup task checkpoint. If the checkpoint lag of the log backup task exceeds this limit, the task will be paused by TiDB Advancer. +- This variable is used to control the maximum allowed checkpoint lag for a log backup task. If a task's checkpoint lag exceeds this limit, TiDB Advancer pauses the task. ### tidb_allow_tiflash_cop New in v7.3.0 From 48a42475cfb2633e96a0c45f6770175ba9538d58 Mon Sep 17 00:00:00 2001 From: xixirangrang Date: Thu, 25 Dec 2025 11:56:15 +0800 Subject: [PATCH 4/6] Update system-variables.md --- system-variables.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/system-variables.md b/system-variables.md index 909458c7072b0..ccab46715cf5f 100644 --- a/system-variables.md +++ b/system-variables.md @@ -1012,7 +1012,7 @@ mysql> SHOW GLOBAL VARIABLES LIKE 'max_prepared_stmt_count'; - Unit: Bytes - This variable is used to control the threshold at which the TiDB server prefers to send read requests to a replica in the same availability zone as the TiDB server when [`tidb_replica_read`](#tidb_replica_read-new-in-v40) is set to `closest-adaptive`. If the estimated result is higher than or equal to this threshold, TiDB prefers to send read requests to a replica in the same availability zone. Otherwise, TiDB sends read requests to the leader replica. -### tidb_advancer_check_point_lag_limit New in v9.0.0 +### tidb_advancer_check_point_lag_limit New in v8.5.5 and v9.0.0 - Scope: GLOBAL - Persists to cluster: Yes From 6a4ccec2e380363fe47df9a45c1ea557f3b1b197 Mon Sep 17 00:00:00 2001 From: Lilian Lee Date: Thu, 25 Dec 2025 17:54:51 +0800 Subject: [PATCH 5/6] Simplify wording --- system-variables.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/system-variables.md b/system-variables.md index ccab46715cf5f..47fdda7840630 100644 --- a/system-variables.md +++ b/system-variables.md @@ -1020,7 +1020,7 @@ mysql> SHOW GLOBAL VARIABLES LIKE 'max_prepared_stmt_count'; - Type: Duration - Default value: `48h0m0s` - Range: `[1s, 8760h0m0s]` -- This variable is used to control the maximum allowed checkpoint lag for a log backup task. If a task's checkpoint lag exceeds this limit, TiDB Advancer pauses the task. +- This variable controls the maximum allowed checkpoint lag for a log backup task. If a task's checkpoint lag exceeds this limit, TiDB Advancer pauses the task. ### tidb_allow_tiflash_cop New in v7.3.0 From 7b93bd219bca97af16ca5e27e9d56de2d8e25d78 Mon Sep 17 00:00:00 2001 From: xixirangrang Date: Thu, 25 Dec 2025 18:13:53 +0800 Subject: [PATCH 6/6] Update system-variables.md --- system-variables.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/system-variables.md b/system-variables.md index 47fdda7840630..2cffb58d2f4ab 100644 --- a/system-variables.md +++ b/system-variables.md @@ -1012,7 +1012,7 @@ mysql> SHOW GLOBAL VARIABLES LIKE 'max_prepared_stmt_count'; - Unit: Bytes - This variable is used to control the threshold at which the TiDB server prefers to send read requests to a replica in the same availability zone as the TiDB server when [`tidb_replica_read`](#tidb_replica_read-new-in-v40) is set to `closest-adaptive`. If the estimated result is higher than or equal to this threshold, TiDB prefers to send read requests to a replica in the same availability zone. Otherwise, TiDB sends read requests to the leader replica. -### tidb_advancer_check_point_lag_limit New in v8.5.5 and v9.0.0 +### tidb_advancer_check_point_lag_limit New in v8.5.5 - Scope: GLOBAL - Persists to cluster: Yes