opt: implement ON DELETE SET NULL/DEFAULT

[RaduBerinde]

Implementing the ON DELETE SET NULL and SET DEFAULT actions. These actions
trigger an update in the child table whenever a row is deleted from the parent.

Release note: None

[cockroach-teamcity]

This change is 

[rytaft]

Reviewed 6 of 6 files at r1.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @andy-kimball and @RaduBerinde)

---

pkg/sql/opt/optbuilder/testdata/fk-on-delete-set-default, line 113 at r1 (raw file):

CREATE TABLE child_multicol (
  c INT PRIMARY KEY,
  p INT DEFAULT (c), q INT DEFAULT (p + 1), r INT DEFAULT (p+q),

[nit] inconsistent formatting of the scalar expressions

---

pkg/sql/opt/optbuilder/testdata/fk-on-delete-set-null, line 6 at r1 (raw file):

exec-ddl
CREATE TABLE child (c INT PRIMARY KEY, p INT REFERENCES parent(p) ON DELETE SET NULL)

how will match simple v. match full interact with this? is it worth adding some tests?

[RaduBerinde]

TFTR!

bors r+

Reviewable status: complete! 0 of 0 LGTMs obtained (and 1 stale) (waiting on @andy-kimball and @rytaft)

---

pkg/sql/opt/optbuilder/testdata/fk-on-delete-set-default, line 113 at r1 (raw file):

Previously, rytaft (Rebecca Taft) wrote…

[nit] inconsistent formatting of the scalar expressions

Done.

---

pkg/sql/opt/optbuilder/testdata/fk-on-delete-set-null, line 6 at r1 (raw file):

Previously, rytaft (Rebecca Taft) wrote…

how will match simple v. match full interact with this? is it worth adding some tests?

There is no difference in the cascade - any rows that had any NULLs on the FK columns will not match in the semi-join so will not result in any cascades.

[craig]

Build failed

• GitHub CI (Cockroach)

[RaduBerinde]

bors r+

[craig]

Build succeeded

• GitHub CI (Cockroach)