post_ID in schema not consistent across tables

[charleshooper]

Since r5078 the largest possible value for wp_posts.ID due to the cast to int is limited to 2,147,483,647 on most 32-bit platforms. The column for wp_comments.comment_post_ID is also an INT-sized value, as opposed to the BIGINT-sized value in wp_posts. I am recommending we reduce the size of the post_IDs in the schema from BIGINT to INT. Doing so will greatly reduce the table and index size for the tables wp_comments, wp_post2cat, wp_postmeta and is just good practice in regards to efficient database design.

See also #3725.

[charleshooper]

Modifies database schema and bumps db_version

[Denis-de-Bernardy]

fixed in 2.8