release-24.1: apiv2,server: filter expensive db queries from sql-over-http

[blathers-crl[bot]]

Backport 1/1 commits from #133075 on behalf of @dhartunian.

/cc @cockroachdb/release

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Retrieving replica counts and region data via the SHOW RANGES FROM DATABASE and SHOW RANGES FROM TABLE queries is extremely costly, especially on a large cluster.

Executing these queries should not be done automatically and it's unclear if the cost of computation is worth the data that the customer can see. It would be better for a customer to explicitly opt-in to computing this data in special cases.

A cluster setting (ui.database_locality_metadata.enabled) has been introduced to allow customers to turn this functionality off if they're managing a large fleet where it's difficult to prevent users from using this feature. By default this data is enabled.

The implementation is admittedly a hack, designed to reduce the size of this diff and the risk of the backport. Implementing this change purely on the client-side resulted in too much code needing to be changed as we would both need to conditionally change the queries being used to load data, and gate them on cluster setting being loaded successfully prior to the SQL requests being made.

Resolves: CRDB-42482

Release note (ops change, ui change): A new cluster setting ui.database_locality_metadata.enabled allows operators to disable loading extended database and table region information in the DB Console Database and Table pages. This information can cause significant CPU load on large clusters with many ranges. Versions of this page from 24.3 onwards do not have this problem. If customers will require this data, they can use the SHOW RANGES FROM {DATABASE| TABLE} query via SQL to compute on-demand.

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Release justification: low-risk opt-in feature that can reduce cluster overload

[blathers-crl[bot]]

Thanks for opening a backport.

Please check the backport criteria before merging:

• [ ] Backports should only be created for serious issues or test-only changes.
• [ ] Backports should not break backwards-compatibility.
• [ ] Backports should change as little code as possible.
• [ ] Backports should not change on-disk formats or node communication protocols.
• [ ] Backports should not add new functionality (except as defined here).
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• [ ] All backports must be reviewed by the owning areas TL. For more information as to how that review should be conducted, please consult the backport policy.

If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

- [ ] There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way. - [ ] The new functionality is additive-only and only runs for clusters which have specifically “opted in” to it (e.g. by a cluster setting). - [ ] New code is protected by a conditional check that is trivial to verify and ensures that it only runs for opt-in clusters. State changes must be further protected such that nodes running old binaries will not be negatively impacted by the new state (with a mixed version test added). - [ ] The PM and TL on the team that owns the changed code have signed off that the change obeys the above rules. - [ ] Your backport must be accompanied by a post to the appropriate Slack channel (#db-backports-point-releases or #db-backports-XX-X-release) for awareness and discussion.

Also, please add a brief release justification to the body of your PR to justify this backport.

[cockroach-teamcity]

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