sql: disallow using cluster_logical_timestamp as column default when backfilling

[Xiang-Gu]

Previously, ADD COLUMN ... DEFAULT cluster_logical_timestamp() would crash the node and leave the table in a corrupt state. The root cause is a nil pointer dereference. This commit fixed it by returning an unimplemented error and hence disallow using this builtin function as default value when backfilling.

Fixes: #98269
Release note (bug fix): fixed a bug as detailed in #98269.

[cockroach-teamcity]

This change is 

[rharding6373]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @Xiang-Gu)

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pkg/sql/backfill/backfill.go line 380 at r1 (raw file):

				if errors.Is(err, colexecerror.ErrNilTxnAccessedInColBackfill) {
					// Issue #98269; Cannot use `cluster_logical_timestamp()` as column default value.
					return roachpb.Key{}, pgerror.WithCandidateCode(err, pgcode.FeatureNotSupported)

Consider using unimplemented.NewWithIssue instead.

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pkg/sql/sem/eval/context.go line 501 at r1 (raw file):

func (ec *Context) GetClusterTimestamp() (*tree.DDecimal, error) {
	if ec.Txn == nil {
		return nil, colexecerror.ErrNilTxnAccessedInColBackfill

GetClusterTimestamp() can be called outside of col backfill, right? It seems like this error is misnamed. Maybe something like ErrNilTxnInClusterContext instead.

[Xiang-Gu]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @rharding6373)

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pkg/sql/backfill/backfill.go line 380 at r1 (raw file):

Previously, rharding6373 (Rachael Harding) wrote…

Consider using unimplemented.NewWithIssue instead.

Done.

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pkg/sql/sem/eval/context.go line 501 at r1 (raw file):

Previously, rharding6373 (Rachael Harding) wrote…

GetClusterTimestamp() can be called outside of col backfill, right? It seems like this error is misnamed. Maybe something like ErrNilTxnInClusterContext instead.

Done.

[Xiang-Gu]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @rharding6373)

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pkg/sql/backfill/backfill.go line 380 at r1 (raw file):

Previously, Xiang-Gu (Xiang Gu) wrote…

Done.

It turns out I cannot. The base error is defined and I can only decorate it with a FeatureNotSupported pgcode. Plus, I don't think creating a issue for this is necessary; my original comments refers to the issue that required this fix. I've updated the comments.

[fqazi]

Reviewed 1 of 8 files at r1, 7 of 7 files at r2, all commit messages.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @rharding6373)

[Xiang-Gu]

TFTR!

bors r+

[craig]

👎 Rejected by code reviews

[rharding6373]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @Xiang-Gu)

[Xiang-Gu]

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 796cf66 to blathers/backport-release-22.1-98696: 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 796cf66 to blathers/backport-release-22.2-98696: 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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