Add virtual table `TiDB_HOT_REGIONS_HISTORY `

[nolouch]

ref #25281

Background

TiDB has a memory table TIDB_HOT_REGIONS that provides information about hotspot regions. But it only shows the current hotspot information. This leads to the fact that when DBAs want to query historical hotspot details, they have no way to find the corresponding hotspot information.

According to the documentation for the current TIDB_HOT_REGIONS table, it can only provides information about recent hotspot regions calculated by PD according to the heartbeat from tikv. It is inconvenient to obtain hotspot regions of past time, and locate which store the region is. For ease of use, we can store extened hotspot region infomation in PD. The DBA can query hotspot regions within a specified period by such statement in TiDB:

SElECT * FROM information_schema.tidb_hot_regions_history WHERE update_time>='2019-04-01 00:00:00' and update_time<='2019-04-01 00:01:00';

Details

Create a new table TIDB_HOT_REGIONS_HISTORY in the INFORMATION_SCHEMAT schema to retrieve history hotspot regions stored by PD periodically.

[IcePigZDB]

• TiDB's relative implmention PRs:
  1. infoschema: add tidb_hot_regions_history virtual table #27373
  2. planner: add extractor for tidb_hot_regions_history #27374
  3. executor: add retriver for tidb_hot_regions_history  #27375
  4. executor: use helper.GetRegionsTableInfo to get region schema for tidb_hot_regions_history #30500

[IcePigZDB]

• Docs
  • information-schema: add tidb_hot_regions_history docs and update tidb_hot_regions docs#6624
  • information-schema: add tidb_hot_regions_history docs and update tidb_hot_regions docs-cn#7164

[nolouch]

Done! thanks @IcePigZDB @qidi1