add support for DEFAULT in insert statements for sequences to the query planner

[mc0]

This will treat DEFAULT as "null" for the purposes of sequences when
running insert statements. This matches with MySQL's documented
behavior and observed resulted.

INSERT INTO t (id) VALUES(DEFAULT);

See for more information:
https://dev.mysql.com/doc/refman/8.0/en/data-type-defaults.html

[systay]

Not following here.

INSERT INTO t VALUES(DEFAULT);

is not the same as

INSERT INTO t VALUES(null);

Shouldn't the planner check that the column is a sequence or something else we have a default value for before accepting this query?

[mc0]

Not following here.

INSERT INTO t VALUES(DEFAULT);

is not the same as

INSERT INTO t VALUES(null);

Shouldn't the planner check that the column is a sequence or something else we have a default value for before accepting this query?

The only place swapBindVariables is called is for swapping out sequences.

[systay]

LGTM

[systay]

Closed by mistake. So sorry.

[sougou]

One minor nit: It's better to move this code into modifyForAutoinc because it's now specific to that context. Otherwise, there's a risk that someone may accidentally reuse this function for other purposes.

[mc0]

I agree with this conceptually. I was just trying to not add another loop for the sake of performance. Should I rename this function instead?

[sougou]

Rename sounds good.

[mc0]

Sorry, I think I misread what you suggested. If I move this code into modifyForAutoinc, I think we'd like this function to be deleted as well. Is that correct?

[sougou]

Right. I think this function was previously reused, but it looks like I inlined it for the other use case.