VReplication: Remove auto_increment clauses for MoveTables to a sharded keyspace

[mattlord]

Description

It's common to move one or more tables from an unsharded keyspace to a sharded one as a subset of tables become too large and must be split — or when moving tables from a standalone MySQL instance to Vitess and sharding them in the process.

For unsharded tables it's standard to use MySQL's auto_increment feature so that a unique Primary Key value is automatically generated and assigned for each row. Once those tables are sharded, however, you DO NOT typically want to use them as each row needs to be unique across ALL shards rather than within a single MySQL instance/shard. You should instead use something generated externally such as some form of a globally/universally unique identifier or Vitess Sequences.

Given this explicit best practice, we should perform this work for you automatically within Vitess by default (with the ability to opt-out) when moving tables from an unsharded keyspace to a sharded one. This avoids potential mistakes down the line (something that does a direct insert in the mysqld instance w/o providing a PK value, expecting a unique one to be generated when it's not) and prevents the user from having to perform other perhaps heavy manual operations such as later running an ALTER TABLE on the tables.

ℹ️ This feature is ONLY added to the vtctldclient implementation while the legacy vtctlclient implementation is left alone so that it can remain frozen and serve as a backup in case an unexpected edge case is encountered with the new client — until it's later removed.

Related Issue(s)

• Fixes: Feature Request: Drop auto_increment from sharded column definitions on MoveTables Create  #15682

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
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• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

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[codecov]

Codecov Report

Attention: Patch coverage is 77.27273% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 68.37%. Comparing base (ffa21e7) to head (306d6ee).
Report is 2 commits behind head on main.

Files	Patch %	Lines
go/vt/vtctl/workflow/materializer.go	50.00%	5 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15679   +/-   ##
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  Coverage   68.37%   68.37%           
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  Files        1556     1556           
  Lines      195051   195120   +69     
=======================================
+ Hits       133365   133416   +51     
- Misses      61686    61704   +18     

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[shlomi-noach]

Looks good! One nit ask for a test change.

[shlomi-noach]

I think it would have been easier to use Walk(), to jump right into a Column definition, but it's fine as it is.

[mattlord]

Thanks! Did I misunderstand what you meant? https://github.com/vitessio/vitess/pull/15679/files#diff-d3a320c7b03791f5d24189e3ae6d7fcac814f4fa1b3d7c02d496b3d8f0adf588R220

[shlomi-noach]

Perfect!