Global Index for partitioned tables

[mjonss]

Enhancement

Development tasks for:
Make GLOBAL INDEX General Available

Stage 1 - full implementation, but Experimental

• Change syntax, to enable (default) LOCAL index, and (explicit) GLOBAL index, Add {LOCAL|GLOBAL} INDEX as explicit syntax #52994
• Move enable global index from configuration to experimental feature flag, tidb_enable_global_index system variable #48825
• Add tests for all index access plans
  • Create issues for handling the index access plans currently not supporting Global indexes (first disable the specific plan, then add support).
• Global index add support for check index/check table #53019
• Add tests for all write transactions (select lock, commit, rollback, different transaction modes, different transaction levels) * (insert, update, delete, select for update, single/multi statement transaction).

Stage 2 - Stabilise / General Available

• Fix reported bugs
• Adjust syntax if needed
• Add more tests if needed
• Enable by default
• Remove experimental flag

[Defined2014]

Maybe support for indexMerge and UnionScan can be added, it seems we are not considering global indexes in those related codes.

Also we need to consider the support of the planner part. Like different cost between global index and local index in some executors.

[311ybb]

please make global index General Available faster, we need it !

[vonwind]

This is an urgently needed feature.