schemachanger/rel: fix race due to failure to clone constraint slots

[ajwerner]

The fundamental race here is that while the slots themselves were being copied by value, the "any" clauses which are a slice were not. The second bug here is that the "inline" values were not being properly reset. That bug could lead to problems when the query was run again in the context of a different element set. We need to reset those inline values too.

Fixes #88628

Release note: None

[cockroach-teamcity]

This change is 

[ajwerner]

In practice this bug was less severe than it sounded -- the values used in these slots are always constants and are never data-dependent constants, so the value we'll fill always ends up being the same unless the query were about structs or strings. We currently never search by strings, but if we did, we would have had a bug. I'm adding some more targeted tests.

[ajwerner]

Alrighty, I wrote a better, lower-level test.

[fqazi]

One minor nit with an incomplete comment

Reviewed 7 of 7 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @ajwerner)

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pkg/sql/schemachanger/rel/query_eval.go line 51 at r1 (raw file):

	for i := range clone {
		// If there are any slots which map to a set of allowed values, we need
		// to clone those values because during query evaluation, we'll

The comment is incomplete here?

[ajwerner]

TFTR!

[ajwerner]

bors r+

[craig]

Build succeeded:

• Bazel Essential CI (Cockroach)

[blathers-crl]

Encountered an error creating backports. Some common things that can go wrong:

1. The backport branch might have already existed.
2. There was a merge conflict.
3. The backport branch contained merge commits.

You might need to create your backport manually using the backport tool.

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error creating merge commit from 8126b7e to blathers/backport-release-22.1-88670: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 22.1.x failed. See errors above.

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error creating merge commit from 8126b7e to blathers/backport-release-22.2-88670: POST https://api.github.com/repos/cockroachdb/cockroach/merges: 409 Merge conflict []

you may need to manually resolve merge conflicts with the backport tool.

Backport to branch 22.2.x failed. See errors above.

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