sql: fix validation of MATCH FULL foreign keys with mixed column types

[thoszhang]

Previously, the internal validation query for MATCH FULL foreign keys checked
for the presence of invalid keys for a set of columns c_1, ..., c_n by using
COALESCE(c_1, ..., c_n) IS NULL, which fails if any of the columns differ in
type because COALESCE requires its arguments to be all of the same type. This
PR fixes the validation query by using c_1 IS NULL AND ... AND c_n IS NULL
instead.

Fixes #42498.

Release note (bug fix): Fixed a bug that would produce a spurious failure with
the error message "incompatible COALESCE expressions" when adding or validating
MATCH FULL foreign key constraints involving composite keys with columns of
differing types.

[cockroach-teamcity]

This change is 

[thoszhang]

This was introduced in 19.1 (along with support for MATCH FULL, I think), but it becomes worse in 19.2 since all FKs get validated by default. I think we should backport to at least 19.2.

[solongordon]

Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @lucy-zhang and @solongordon)

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pkg/sql/check.go, line 73 at r1 (raw file):

// SELECT s.a_id, s.b_id, s.pk1, s.pk2 FROM child@c_idx
// WHERE
//   NOT ((a_id IS NULL AND b_id IS NULL) OR (a_id IS NOT NULL AND b_id IS NOT NULL))

This is unrelated to your fix but seems like this could be simplified to WHERE (a_id IS NULL OR b_id IS NULL) AND (a_id IS NOT NULL OR b_id IS NOT NULL).

[thoszhang]

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

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pkg/sql/check.go, line 73 at r1 (raw file):

Previously, solongordon (Solon) wrote…

This is unrelated to your fix but seems like this could be simplified to WHERE (a_id IS NULL OR b_id IS NULL) AND (a_id IS NOT NULL OR b_id IS NOT NULL).

Done.

[thoszhang]

TFTR!

bors r+

[craig]

Build succeeded

• GitHub CI (Cockroach)