Bad PRIMARY key for the table wp_post2cat

[michel v]

Using a rel_id field as a PRIMARY key to ensure relationships are unique is rather useless. We never use rel_id in the code.
A better approach would be to get rid of rel_id, and set the PRIMARY key on the tuple post_id and category_id.

[markjaquith]

still worth fixing?

[ketsugi]

A quick patch: removes the rel_id columns from link2cat and post2cat, replaces the primary keys with a tuple, and bumps the database version by 1.

[rob1n]

Wouldn't setting both post_id and category_id as PRIMARY's force them to be unique? Neither will be unique, eventually...

[DD32]

Wouldn't setting both post_id and category_id as PRIMARY's force them to be unique?
Not if they're added as a tuple, ie a pair. The primary key would be a combination of post_id AND category_id.
I'm not sure myself if it'd be more optimized that way, or if it was a single index on either.

[rob1n]

I'd say a simple INDEX on both category_ID and post_ID would be nice. Any devs have feedback?

[rob1n]

Oh, and taking out rel_id too.

[matt]

I like the new primary key. I think it's worth also having an index on category_id re #3900.

[rob1n]

​http://trac.wordpress.org/ticket/3900#comment:4

Should we merge tickets?

[rob1n]

I'll take another look when #3900 is committed.

[ryan]

post2cat is gone in 2.3.