release-24.3: schemachangerccl: split backup tests

[fqazi]

Previously, all of the CCL tests would run in a single package. We would observe test flakes the global timeout for the package was too low. To address this, this package shards the backup tests similar to newer branches.

Fixes: #160455

Release note: None
Release justification: test only change

[blathers-crl]

Thanks for opening a backport.

Before merging, please confirm that it falls into one of the following categories (select one):

• Non-production code changes. Includes test-only changes, build system changes, etc.
• Fixes for serious issues. Defined in the policy as correctness, stability, or security issues, data corruption/loss, significant performance regressions, breaking working and widely used functionality, or an inability to detect and debug production issues.
• Other approved changes. These changes must be gated behind a disabled-by-default feature flag unless there is a strong justification not to.

Add a brief release justification to the PR description explaining your selection.

Also, confirm that the change does not break backward compatibility and complies with all aspects of the backport policy.

All backports must be reviewed by the TL and EM for the owning area.

[blathers-crl]

Your pull request contains more than 1000 changes. It is strongly encouraged to split big PRs into smaller chunks.

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[cockroach-teamcity]

This change is 

[blathers-crl]

✅ PR #160578 is compliant with backport policy

Confidence: high
Backward compatible: true
Explanation: This pull request is exempt from the standard backport policy requirements as it is a test-only change, which falls under the non-production code exception. The PR body explicitly mentions 'Release justification: test only change', which supports this exemption. All modifications are within the pkg/ccl/schemachangerccl/ directory, primarily impacting test files and configurations, specifically creating new test directories and test files. These changes are focused on sharding backup tests into separate packages to address test flakes from global timeout issues.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is dev-inf.}

[rafiss]

I had a few questions/comments:

• Do you know why this had to be done differently than #159914 ?
• Should we get this into 25.2 and 25.3 also?
• I thought we were discussing only backporting #160344 to skip the restore_all_tables case? why is this splitting PR needed too?
• nit: this PR names the package scbackuptestmrccl, but on master it's named sctestbackupmrccl

[fqazi]

Do you know why this had to be done differently than #159914 ?

The 24.3 branch was missing enhancements to split the backup tests in general, so part of the changes is to split the backup tests for single region, and a minor changes to make MultiRegionTestClusterFactory accessible.

Should we get this into 25.2 and 25.3 also?

So, there is a manual backport that adds a split on 25.3: #160574. I'll use that to get one on 25.2 as well.

I thought we were discussing only backporting #160344 to skip the restore_all_tables case? why is this splitting PR needed too?

The number of multiregion tests isn't really large on 24.3, we have about 11 of them. The most complex schema change CREATE INDEX which is 7 stages, so I'm not sure if it would buy us too much versus better sharding. I think we can avoid the restore_all_tables changes on this branch if the sharding is sufficient. Let me know what you think.

nit: this PR names the package scbackuptestmrccl, but on master it's named sctestbackupmrccl

Fixed

[rafiss]

The most complex schema change CREATE INDEX which is 7 stages, so I'm not sure if it would buy us too much versus better sharding. I think we can avoid the restore_all_tables changes on this branch if the sharding is sufficient. Let me know what you think.

I see, in that case it seems fine to only do the restore_all_tables change in master and recent branches.

[fqazi]

@rafiss TFTR!