v8.5.5: doc updates for v8.5.5 #22305

qiancai · 2026-01-13T01:51:13Z

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This PR covers all doc updates for v8.5.5 that have been merged to the feature/preview-v8.5.5 branch.

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This PR is translated from: v8.5.5: doc updates for v8.5.5 docs-cn#21265
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…rol log backup checkpoint lag (#21481) (#22239)

* Add temp.md * Delete temp.md * toc, br: add compact log backup * Update wording * Remove example output * Apply suggestions from code review Co-authored-by: 山岚 <36239017+YuJuncen@users.noreply.github.com> * Apply suggestions from code review Co-authored-by: xixirangrang <hfxsd@hotmail.com> * Apply suggestions from code review Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com> * Apply suggestions from code review --------- Co-authored-by: Lilian Lee <lilin@pingcap.com> Co-authored-by: 山岚 <36239017+YuJuncen@users.noreply.github.com> Co-authored-by: xixirangrang <hfxsd@hotmail.com> Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

…2168) * added translation (by Claude 3.7 Sonnet Thinking) * tweaking some terms * Refine wording and format Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com> * Update wording * Update br/br-pitr-manual.md Co-authored-by: xixirangrang <hfxsd@hotmail.com> * Update version wording Co-authored-by: Grace Cai <qqzczy@126.com> --------- Co-authored-by: hillium <yu745514916@live.com> Co-authored-by: Lilian Lee <lilin@pingcap.com> Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: xixirangrang <hfxsd@hotmail.com> Co-authored-by: Grace Cai <qqzczy@126.com>

…nd the usage of pitr id map (#21078) (#22200)

…data (#20492) (#22236)

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gemini-code-assist · 2026-01-13T01:51:41Z

Summary of Changes

Hello @qiancai, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request consolidates and updates the documentation for TiDB v8.5.5, primarily focusing on the Backup & Restore (BR) tool. It introduces comprehensive guides for the new "Compact Log Backup" feature, which optimizes Point-in-Time Recovery (PITR) by converting log backups to SST files. The updates also significantly enhance PITR operations with new capabilities like filtered restores, concurrent execution, and better integration with ongoing log backups. Furthermore, the documentation details improvements to checkpoint restore mechanisms, introduces a physical system table restore option, and describes new system variables related to log backup and circuit breakers, ensuring users have up-to-date information on these critical features.

Highlights

New "Compact Log Backup" Feature Documentation: Introduced a new document explaining how to improve Point-in-Time Recovery (PITR) efficiency by compacting log backups into SST format, including its overview, limitations, and manual usage.
Enhanced Point-in-Time Recovery (PITR) Capabilities: Documentation updates cover new features for PITR, including restoring data using filters, performing concurrent restore operations, and improved compatibility with ongoing log backup tasks.
Checkpoint Restore Mechanism Updates: Detailed explanations for storing checkpoint data, differentiating between downstream cluster and external storage options, and clarifying persistence of pitr_id_map.
Physical System Table Restore: Introduced the --fast-load-sys-tables parameter for br restore to enable physical restoration of system tables, offering an alternative to logical restoration.
New System Variables: Added documentation for tidb_advancer_check_point_lag_limit (controlling log backup checkpoint lag) and tidb_cb_pd_metadata_error_rate_threshold_ratio (for TiDB circuit breaker).
Improved Restore Process Visibility: Updated progress bar outputs for both snapshot and PITR restores to include more detailed metrics like Split&Scatter Region, Download&Ingest SST, and Restore Pipeline.
Table Mode During Restore: Clarified that tables are set to restore mode during data restoration, preventing read/write operations until completion.

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Code Review

This pull request includes several documentation updates for the v8.5.5 release, primarily focusing on Backup & Restore (BR) features and new system variables. The changes are comprehensive and well-structured. I've added a few minor suggestions to improve clarity, fix grammar, and add helpful links to related documentation. Overall, the updates are clear and will be beneficial for users.

gemini-code-assist · 2026-01-13T01:53:41Z

br/br-checkpoint-restore.md

+> **Note:**
+>
+> To ensure compatibility with clusters of earlier versions, starting from v8.5.5, if the system table `mysql.tidb_pitr_id_map` does not exist in the restore cluster and the `--checkpoint-storage` parameter is not specified, the `pitr_id_map` data will be written to the log backup directory. The file name is `pitr_id_maps/pitr_id_map.cluster_id:{downstream-cluster-ID}.restored_ts:{restored-ts}`.


This note appears to be a duplicate of the one on lines 94-96 and is placed in a confusing section. The condition --checkpoint-storage parameter is not specified describes the default behavior, which is already covered in the "store checkpoint data in the downstream cluster" section. To avoid confusion, I suggest removing this note.

gemini-code-assist · 2026-01-13T01:53:41Z

br/br-compact-log-backup.md

+
+> **Note:**
+>
+> - If the `--load-creds` option is included when you execute the preceding command, the encoded Base64 string contains credential information loaded from the current BR environment. Note to ensure proper security and access control.


The phrase "Note to ensure" is a bit awkward. For better clarity and to follow the style guide's recommendation of using the second person, I suggest rephrasing it.

Suggested change

> - If the `--load-creds` option is included when you execute the preceding command, the encoded Base64 string contains credential information loaded from the current BR environment. Note to ensure proper security and access control.

> - If you include the `--load-creds` option when you execute the preceding command, the encoded Base64 string contains credential information loaded from the current BR environment. Be sure to handle this string with proper security and access control.

gemini-code-assist · 2026-01-13T01:53:41Z

br/br-snapshot-guide.md

 - Starting from BR v5.1.0, when you back up snapshots, BR automatically backs up the **system tables** in the `mysql` schema, but does not restore these system tables by default.
 - Starting from v6.2.0, BR lets you specify `--with-sys-table` to restore **data in some system tables**.
 - Starting from v7.6.0, BR enables `--with-sys-table` by default, which means that BR restores **data in some system tables** by default.
+- Starting from v8.5.5, BR introduces the `--fast-load-sys-tables` parameter to support physical restore of system tables. This parameter is enabled by default. This approach uses the `RENAME TABLE` DDL statement to atomically swap the system tables in the `__TiDB_BR_Temporary_mysql` database with the system tables in the `mysql` database. Unlike the logical restoration of system tables using the `REPLACE INTO` SQL statement, physical restoration completely overwrites the existing data in the system tables.


To improve readability and provide more context for the user, consider adding links to the documentation for RENAME TABLE and REPLACE INTO.

Suggested change

- Starting from v8.5.5, BR introduces the `--fast-load-sys-tables` parameter to support physical restore of system tables. This parameter is enabled by default. This approach uses the `RENAME TABLE` DDL statement to atomically swap the system tables in the `__TiDB_BR_Temporary_mysql` database with the system tables in the `mysql` database. Unlike the logical restoration of system tables using the `REPLACE INTO` SQL statement, physical restoration completely overwrites the existing data in the system tables.

- Starting from v8.5.5, BR introduces the `--fast-load-sys-tables` parameter to support physical restore of system tables. This parameter is enabled by default. This approach uses the [`RENAME TABLE`](/sql-statements/sql-statement-rename-table.md) DDL statement to atomically swap the system tables in the `__TiDB_BR_Temporary_mysql` database with the system tables in the `mysql` database. Unlike the logical restoration of system tables using the [`REPLACE INTO`](/sql-statements/sql-statement-replace.md) SQL statement, physical restoration completely overwrites the existing data in the system tables.

gemini-code-assist · 2026-01-13T01:53:42Z

br/br-snapshot-manual.md

+
 When the backup and restore feature backs up data, it stores statistics in JSON format within the `backupmeta` file. When restoring data, it loads statistics in JSON format into the cluster. For more information, see [LOAD STATS](/sql-statements/sql-statement-load-stats.md).

+Starting from v8.5.5, BR introduces the `--fast-load-sys-tables` parameter, which is enabled by default. When restoring data to a new cluster using the `br` command-line tool, and the IDs of tables and partitions between the upstream and downstream clusters can be reused (otherwise, BR will automatically fall back to logically load statistics), enabling `--fast-load-sys-tables` lets BR to first restore the statistics-related system tables to the temporary system database `__TiDB_BR_Temporary_mysql`, and then atomically swap these tables with the corresponding tables in the `mysql` database using the `RENAME TABLE` statement.


There's a minor grammatical error ('lets BR to first restore'). Also, for better readability, consider adding a link to the RENAME TABLE documentation.

Suggested change

Starting from v8.5.5, BR introduces the `--fast-load-sys-tables` parameter, which is enabled by default. When restoring data to a new cluster using the `br` command-line tool, and the IDs of tables and partitions between the upstream and downstream clusters can be reused (otherwise, BR will automatically fall back to logically load statistics), enabling `--fast-load-sys-tables` lets BR to first restore the statistics-related system tables to the temporary system database `__TiDB_BR_Temporary_mysql`, and then atomically swap these tables with the corresponding tables in the `mysql` database using the `RENAME TABLE` statement.

Starting from v8.5.5, BR introduces the `--fast-load-sys-tables` parameter, which is enabled by default. When restoring data to a new cluster using the `br` command-line tool, and the IDs of tables and partitions between the upstream and downstream clusters can be reused (otherwise, BR will automatically fall back to logically load statistics), enabling `--fast-load-sys-tables` lets BR first restore the statistics-related system tables to the temporary system database `__TiDB_BR_Temporary_mysql`, and then atomically swap these tables with the corresponding tables in the `mysql` database using the [`RENAME TABLE`](/sql-statements/sql-statement-rename-table.md) statement.

gemini-code-assist · 2026-01-13T01:53:42Z

br/br-snapshot-manual.md

+
+> **Note:**
+>
+> Unlike the logical restoration of system tables using the `REPLACE INTO` SQL statement, physical restoration completely overwrites the existing data in the system tables.


To improve readability, consider adding a link to the REPLACE INTO documentation.

Suggested change

> Unlike the logical restoration of system tables using the `REPLACE INTO` SQL statement, physical restoration completely overwrites the existing data in the system tables.

> Unlike the logical restoration of system tables using the [`REPLACE INTO`](/sql-statements/sql-statement-replace.md) SQL statement, physical restoration completely overwrites the existing data in the system tables.

…mary (#21155) (#22249)

…22306) Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com> Co-authored-by: Aolin <aolinz@outlook.com> Co-authored-by: Grace Cai <qqzczy@126.com>

ti-chi-bot and others added 13 commits December 29, 2025 02:20

v8.5.5 br: add variable tidb_advancer_check_point_lag_limit to cont…

2225bb9

…rol log backup checkpoint lag (#21481) (#22239)

v8.5.5: Add circuit breaker variable (#20129) (#22171)

dd233dc

Merge branch 'release-8.5' into feature/preview-v8.5.5

8e9d2d2

v8.5.5 br: remove outdated PITR limitation (#22262) (#22264)

3e6d7e6

v8.5.5 br: pitr filter feature release doc (#21109) (#22199)

2e6ca82

v8.5.5 restore: update the definition of the parameter --load-stats a…

17b506f

…nd the usage of pitr id map (#21078) (#22200)

v8.5.5 br: support pitr filter and concurrent restore (#21835) (#22201)

15ee7a0

v8.5.5 br: pitr restore mode (#21254) (#22238)

f9a1834

v8.5.5 br: provide a storage target option for BR restore checkpoint …

3d1c460

…data (#20492) (#22236)

v8.5.5 br: improve visualization of BR (#20493) (#22237)

14f5dc5

Merge branch 'release-8.5' into feature/preview-v8.5.5

846f118

ti-chi-bot bot added the missing-translation-status This PR does not have translation status info. label Jan 13, 2026

ti-chi-bot bot added the size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. label Jan 13, 2026

gemini-code-assist bot reviewed Jan 13, 2026

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ti-chi-bot and others added 8 commits January 13, 2026 02:49

v8.5.5 br: add ddl job none error report (#22300) (#22308)

157a642

v8.5.5: add config for graceful shutdown (#22158)

5d9eb98

Merge branch 'release-8.5' into feature/preview-v8.5.5

d68ac51

v8.5.5: Add index lookup push down content (#22196) (#22252)

0a8c7a1

v8.5.5: include storage engines in slow query logs and statements sum…

fd00a09

…mary (#21155) (#22249)

v8.5.5: add doc for async-batch-get (#22152) (#22311)

e33ffab

Merge branch 'release-8.5' into feature/preview-v8.5.5

7c03ee9

v8.5.5 pd,tidb: support affinity schedule (#22270) (#22315)

28c2a0d

ti-chi-bot bot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. and removed size/XL Denotes a PR that changes 500-999 lines, ignoring generated files. labels Jan 14, 2026

ti-chi-bot added 2 commits January 14, 2026 01:31

v8.5.5: add store limit support (#22297) (#22314)

d0f71b3

v8.5.5: Add unified.cpu-threshold config (#22167) (#22312)

d6c3e74

ti-chi-bot and others added 2 commits January 14, 2026 10:03

v8.5.5 scheduler: network slow store scheduler enhancement (#22269) (#…

e42b42f

…22306) Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com> Co-authored-by: Aolin <aolinz@outlook.com> Co-authored-by: Grace Cai <qqzczy@126.com>

v8.5: bump up the latest version to v8.5.5 (#22322)

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qiancai commented Jan 13, 2026 •

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	> - If the `--load-creds` option is included when you execute the preceding command, the encoded Base64 string contains credential information loaded from the current BR environment. Note to ensure proper security and access control.
	> - If you include the `--load-creds` option when you execute the preceding command, the encoded Base64 string contains credential information loaded from the current BR environment. Be sure to handle this string with proper security and access control.


		When the backup and restore feature backs up data, it stores statistics in JSON format within the `backupmeta` file. When restoring data, it loads statistics in JSON format into the cluster. For more information, see [LOAD STATS](/sql-statements/sql-statement-load-stats.md).

		Starting from v8.5.5, BR introduces the `--fast-load-sys-tables` parameter, which is enabled by default. When restoring data to a new cluster using the `br` command-line tool, and the IDs of tables and partitions between the upstream and downstream clusters can be reused (otherwise, BR will automatically fall back to logically load statistics), enabling `--fast-load-sys-tables` lets BR to first restore the statistics-related system tables to the temporary system database `__TiDB_BR_Temporary_mysql`, and then atomically swap these tables with the corresponding tables in the `mysql` database using the `RENAME TABLE` statement.

	> Unlike the logical restoration of system tables using the `REPLACE INTO` SQL statement, physical restoration completely overwrites the existing data in the system tables.
	> Unlike the logical restoration of system tables using the [`REPLACE INTO`](/sql-statements/sql-statement-replace.md) SQL statement, physical restoration completely overwrites the existing data in the system tables.

v8.5.5: doc updates for v8.5.5 #22305

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