Support Global Index for Partition Table

[tiancaiamao]

Description

In the current table partition implementation, a partition and its indices are encoded to the same key-value range.

table t
...
partition1 
-- data start key
-- data end key
-- index start key
-- index end key
...

...
partition2
-- data start key
-- data end key
-- index start key
-- index end key
...

The global index would require another kind of encoding schema:

table t
...
partition1 
-- data start key
-- data end key
...

...
partition2
-- data start key
-- data end key
...

index
-- index start key
-- index end key
...

The most challenging part of this task is keeping compatible with the older versioned TiDB.

[zz-jason]

Haven't found that MySQL supports the global index for the partition table. I found that there a discussion about supporting global index in PostgreSQL: https://www.percona.com/blog/2019/11/20/proposal-for-global-indexes-in-postgresql/

@morgo do you have any idea about this?

[morgo]

You are correct, it is not supported.

cc @mjonss

[zz-jason]

close since it's duplicated with #18032