bug: should use executor_id to count mview creation progress

[BugenZhao]

a fragment contains more than one chain operator and we need to take care

Yes. I believe there will some problems with the current MV on MV creation reporting since we're using the actor id. 😢

Originally posted by @BugenZhao in #6233 (comment)

• feat(meta): track the progress of creating mview #2773

[BugenZhao]

#6270 will be a prerequisite.

[github-actions]

This issue has been open for 60 days with no activity. Could you please update the status? Feel free to continue discussion or close as not planned.

[BugenZhao]

This is not a problem anymore, as there's no chance that two Backfill executors reside in the same actor. Otherwise,

• If they are for the same table (like self-join), they should be shared.
• If they are for different tables, it's impossible because different upstream tables have different distribution in the optimizer and won't be backfilled in the same fragment.

[xxchan]

In theory, we can have multiple singleton executors in the same fragment (e.g., count(*) mv, or StreamValues). In our current code, it seems this won't happen, since JOIN/UNION will force a hash shard to inputs, and doesn't have the specialization for 2 singleton inputs.