plugin for returning random rows in a table

Selecting random rows from a table is a historicity hard problem. This is because the distribution of row values isn't evident.

"Workarounds" have existed for a while - http://jan.kneschke.de/projects/mysql/order-by-rand/ - fairly intrusive however.

Using engine independent statistics these are available in mariadb https://mariadb.com/kb/en/mariadb/engine-independent-table-statistics/.

To solve exposing a fake table it should be able to get a clean SQL to get random rows.

Like https://mariadb.com/kb/en/mariadb/sequence/ this should be a table discover https://mariadb.com/kb/en/mariadb/table-discovery/.

Mode of operations could be:

ANALYZE TABLE xxx PERSISTENT FOR ALL;

INSTALL SONAME "ha_rand";

SELECT * FROM rand_xxx_col1_5;

The select would return 5 random rows from the table xxx based on the distribution of col1.

Its use a a full member should be returned:

SELECT r.id, other.id FROM rand_xxx_col1_5 r JOIN other on r.id=other.id;

Goals in order:

1. Initial table discovery and returning tables
2. Participation in optimizer negotiation
3. Ensuring a unique result - probably desirable from an expected use however altering the table syntax to have a flag as part of the name for this
4. Make the table modifiable

I'm willing to mentor this, co-mentors with a good knowledge of the storage API and table discovery would be much appreciated