sql: add constraint name to constraint error

[alex-berger]

Add constraint name to error for unique constraint, check constraintand foreign key constraint violations. Those constraint names are then propagated over the PostgreSQL wire protocol and will show up for example in JDBC exceptions (org.postgresql.util.PSQLException#getServerErrorMessage().getConstraint()). This commit improves PostgreSQL compatibility.

Release note: Improve PosgreSQL wire protocol compatibility by adding constraint name to sql errors.

[cockroach-teamcity]

All committers have signed the CLA.

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[cockroach-teamcity]

This change is 

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[yuzefovich]

Thanks! I just have a couple of nits.

nit: the commit message should have a title, a body, and a release note (basically what you have in the PR description).

nit: the title of the commit message (and the PR) should start with the name of the package that has changed and the words should be in lower-case, i.e. we want something like sql: add constraint name to errors.

nit: for the release note, we should specify a category, I think in this case it would be Release note (sql change): ....

Reviewed 2 of 2 files at r1.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @alex-berger)

---

pkg/sql/row/errors.go, line 98 at r1 (raw file):

	}

	error := pgerror.Newf(pgcode.UniqueViolation,

super nit: it might be good to not declare a local variable and return the error right away for consistency with other changes.

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[yuzefovich]

Thanks!

bors r=yuzefovich

[craig]

Build succeeded:

• GitHub CI (Cockroach)