Skip to content

Commit

Permalink
Merge branch 'release-notes-v8.0.0' of https://github.com/hfxsd/docs …
Browse files Browse the repository at this point in the history 
…into pr/16599
  • Loading branch information
@lilin90
lilin90 committed Mar 28, 2024
2 parents f025c2b + 7e0443f commit 63015bf
Showing 1 changed file with 9 additions and 15 deletions.
24 changes: 9 additions & 15 deletions releases/release-8.0.0.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,7 +47,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v8.0/quick-start-with-
<tr>
<td rowspan="1">DB Operations and Observability</td>
<td>Support monitoring index usage statistics </td>
<td>Proper index design is a crucial prerequisite for improving database performance. TiDB v8.0.0 introduces the <a href="https://docs.pingcap.com/tidb/v8.0/information-schema-tidb-index-usage"><code>INFORMATION_SCHEMA.TIDB_INDEX_USAGE</code></a> table and the <a href="https://docs.pingcap.com/tidb/v8.0/sys-schema"><code>sys.schema_unused_index</code></a> view to provide usage statistics of indexes. This feature helps you assess the efficiency of indexes in the database and optimize the index design.</td>
<td>Proper index design is a crucial prerequisite to maintaining database performance. TiDB v8.0.0 introduces the <a href="https://docs.pingcap.com/tidb/v8.0/information-schema-tidb-index-usage"><code>INFORMATION_SCHEMA.TIDB_INDEX_USAGE</code></a> table and the <a href="https://docs.pingcap.com/tidb/v8.0/sys-schema"><code>sys.schema_unused_index</code></a> view to provide usage statistics of indexes. This feature helps you assess the efficiency of indexes in the database and optimize the index design.</td>
</tr>
<tr>
<td rowspan="2">Data Migration</td>
Expand Down Expand Up @@ -209,7 +209,7 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v8.0/quick-start-with-

By default, the optimizer does not select [invisible indexes](/sql-statements/sql-statement-create-index.md#invisible-index). This mechanism is usually used to evaluate whether to delete an index. If there is uncertainty about the potential performance impact of deleting an index, you have the option to set the index to invisible temporarily and promptly restore it to visible when needed.

Starting from v8.0.0, you can set the session-level system variable [`tidb_opt_use_invisible_indexes`](/system-variables.md#tidb_opt_use_invisible_indexes-new-in-v800) to `ON` to make the current session recognize and use invisible indexes. With this feature, you can create a new index and test its performance by setting the index to invisible first, and then modifying the system variable in the current session for testing without affecting other sessions. This improvement enhances the safety of performance tuning and helps to improve the stability of production databases.
Starting from v8.0.0, you can set the session-level system variable [`tidb_opt_use_invisible_indexes`](/system-variables.md#tidb_opt_use_invisible_indexes-new-in-v800) to `ON` to make the current session aware of invisible indexes. With this feature, you can create a new index and test its performance by making the index visible first, and then modifying the system variable in the current session for testing without affecting other sessions. This improvement enhances the safety of SQL tuning and helps to improve the stability of production databases.

For more information, see [documentation](/sql-statements/sql-statement-create-index.md#invisible-index).

Expand All @@ -227,16 +227,16 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v8.0/quick-start-with-

* Support monitoring index usage statistics [#49830](https://github.com/pingcap/tidb/issues/49830) @[YangKeao](https://github.com/YangKeao)

Proper index design is a crucial prerequisite for improving database performance. TiDB v8.0.0 introduces the [`INFORMATION_SCHEMA.TIDB_INDEX_USAGE`](/information-schema/information-schema-tidb-index-usage.md) table, which records usage statistics of all indexes on the current TiDB node, including the following information:
Proper index design is a crucial prerequisite to maintaining database performance. TiDB v8.0.0 introduces the [`INFORMATION_SCHEMA.TIDB_INDEX_USAGE`](/information-schema/information-schema-tidb-index-usage.md) table, which records the statistics of all indexes on the current TiDB node, including the following information:

* The cumulative execution count of statements that scan the index
* The total number of rows scanned when accessing the index
* The selectivity distribution when scanning the index
* The time of the most recent access to the index

With this information, you can identify indexes that are not used by the optimizer and indexes with poor filtering effects, thereby optimizing index design to improve database performance.
With this information, you can identify indexes that are not used by the optimizer and indexes with poor selectivity, thereby optimizing index design to improve database performance.

Additionally, TiDB v8.0.0 introduces a view [`sys.schema_unused_index`](/sys-schema.md), which is compatible with MySQL. This view records indexes that have not been used since the last start of TiDB. For clusters upgraded from versions earlier than v8.0.0, the `sys` schema and the views in it are not created automatically. You can manually create them by referring to [`sys`](/sys-schema.md).
Additionally, TiDB v8.0.0 introduces a view [`sys.schema_unused_index`](/sys-schema.md), which is compatible with MySQL. This view shows indexes that have not been used since the last start of TiDB instances. For clusters upgraded from versions earlier than v8.0.0, the `sys` schema and the views are not created automatically. You can manually create them by referring to [`sys`](/sys-schema.md).

For more information, see [documentation](/information-schema/information-schema-tidb-index-usage.md).

Expand Down Expand Up @@ -392,11 +392,6 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v8.0/quick-start-with-
- MemoryTracker can track the memory usage of the `MemTableReaderExec` operator [#51456](https://github.com/pingcap/tidb/issues/51456) @[wshwsh12](https://github.com/wshwsh12)
- Support canceling queries that are being spilled [#50511](https://github.com/pingcap/tidb/issues/50511) @[wshwsh12](https://github.com/wshwsh12)
- Support loading Regions in batch from PD to speed up the conversion process from the KV range to Regions when querying large tables [#51326](https://github.com/pingcap/tidb/issues/51326) @[SeaRise](https://github.com/SeaRise)
<!-- qiancai -->
- Fix the issue that the `AUTO_INCREMENT` attribute causes non-consecutive IDs due to unnecessary transaction conflicts when assigning auto-increment IDs [#50819](https://github.com/pingcap/tidb/issues/50819) @[tiancaiamao](https://github.com/tiancaiamao)
- Fix the issue of incomplete stack information in TiDB logs for some errors [#50849](https://github.com/pingcap/tidb/issues/50849) @[tiancaiamao](https://github.com/tiancaiamao)
- Fix the issue of excessive memory usage in some queries when the number in the `LIMIT` clause is too large [#51188](https://github.com/pingcap/tidb/issues/51188) @[Defined2014](https://github.com/Defined2014)
- Fix the issue that the TTL feature causes data hotspots due to incorrect data range splitting in certain scenarios [#51527](https://github.com/pingcap/tidb/issues/51527) @[lcwangchao](https://github.com/lcwangchao)

+ TiKV

Expand Down Expand Up @@ -518,11 +513,10 @@ Quick access: [Quick start](https://docs.pingcap.com/tidb/v8.0/quick-start-with-
- Fix the issue that Opentracing does not work correctly [#50508](https://github.com/pingcap/tidb/issues/50508) @[Defined2014](https://github.com/Defined2014)
- Fix the issue that the error message is not complete when `ALTER INSTANCE RELOAD TLS` reports an error [#50699](https://github.com/pingcap/tidb/issues/50699) @[dveeden](https://github.com/dveeden)
<!-- qiancai -->
修复 AUTO_INCREMENT 属性在分配自增 ID 时，由于不必要的事务冲突导致 ID 不连续的问题 [#50819](https://github.com/pingcap/tidb/issues/50819) @[tiancaiamao](https://github.com/tiancaiamao)
修复 TiDB 日志中某些报错栈信息不完全的问题 [#50849](https://github.com/pingcap/tidb/issues/50849) @[tiancaiamao](https://github.com/tiancaiamao)
修复系统变量 @@tidb_server_memory_limit 更新时，一些内部状态没有及时更新的问题 [#48180](https://github.com/pingcap/tidb/issues/48180) @[hawkingrei](https://github.com/hawkingrei)
修复当 `LIMIT` 子句的数字过大时，一些查询的内存使用过大的问题 [#51188](https://github.com/pingcap/tidb/issues/51188) @[Defined2014](https://github.com/Defined2014)
修复 TTL 功能在某些情况下因没有正确切分数据范围而造成热点的问题 [#51527](https://github.com/pingcap/tidb/issues/51527) @[lcwangchao](https://github.com/lcwangchao)
- Fix the issue that the `AUTO_INCREMENT` attribute causes non-consecutive IDs due to unnecessary transaction conflicts when assigning auto-increment IDs [#50819](https://github.com/pingcap/tidb/issues/50819) @[tiancaiamao](https://github.com/tiancaiamao)
- Fix the issue of incomplete stack information in TiDB logs for some errors [#50849](https://github.com/pingcap/tidb/issues/50849) @[tiancaiamao](https://github.com/tiancaiamao)
- Fix the issue of excessive memory usage in some queries when the number in the `LIMIT` clause is too large [#51188](https://github.com/pingcap/tidb/issues/51188) @[Defined2014](https://github.com/Defined2014)
- Fix the issue that the TTL feature causes data hotspots due to incorrect data range splitting in certain scenarios [#51527](https://github.com/pingcap/tidb/issues/51527) @[lcwangchao](https://github.com/lcwangchao)
<!-- hfxsd -->
- Fix the issue that the `SET` statement does not take effect when it appears on the first line of an explicit transaction [#51387](https://github.com/pingcap/tidb/issues/51387) @[YangKeao](https://github.com/YangKeao)
- Fix the issue that querying JSON of `BINARY` type might cause an error in some cases [#51547](https://github.com/pingcap/tidb/issues/51547) @[YangKeao](https://github.com/YangKeao)
Expand Down

0 comments on commit 63015bf

Please sign in to comment.