OnlineDDL Scheduler

[earayu]

We talk about OnlineDDL Executor here.

doc: https://github.com/vitessio/vitess/blob/main/doc/design-docs/OnlineDDLScheduler.md

[earayu]

Fun Fact:

engine.OnlineDDL would add some hints ahead of DDL statement in this function: NewOnlineDDL(...)

-- Origin DDL Statement 
create table t3 (c1 int primary key);

-- DDL After rewritten
create /*vt+ uuid="34383663343930635f353039325f313165655f396461325f666163383733643365366365" context="7674676174653a33316262663162322d353039322d313165652d396461322d666163383733643365366365" table="7433" strategy="6f6e6c696e65" options="" */ table t3 (
	c1 int primary key
)

[earayu]

If there are frequent timeouts when debugging vttablet, you can configure the queryserver-config-query-timeout parameter.

[gerayking]

got it

[earayu]

Check your knowledge of OnlineDDL:

• The meaning of every column of system table schema_migrations

[earayu]

states & transitions

[gerayking]

For the onlineDDL.executor connection pool, why do we create new connections instead of utilizing all the connections available in the connection pool? For example, all sql execute by execQuery