apidb tests on join vs cgimap cache speed

some apidb tests

-- tweak range and modulo value to get right number of nodes and changesets

select count(*) from (select distinct n.changeset_id from current_nodes n where n.id between
2329800000 and 2347300000 and n.id % 10 =0) as changesets;
select count(*) from current_nodes n where n.id between
2329800000 and 2347300000 and n.id % 10 =0;

-- JOIN
explain analyze select n.id, n.changeset_id, u.id, u.display_name from current_nodes
 n join changesets c on n.changeset_id = c.id join users u on c.user_id =
 u.id where n.id between 2329800000 and 2347300000 and n.id % 10 =0; -- 15-19ms

 -- standalone
 explain analyze select n.id, n.changeset_id from current_nodes n where n.id between
2329800000 and 2347300000 and n.id % 10 =0; -- 15ms 

-- pick some random changesets from this list
select distinct n.changeset_id from current_nodes n where n.id between
2329800000 and 2347300000 and n.id % 10 =0 LIMIT 20;

-- plug them in here in the cache-populating query
explain analyze select u.id, u.display_name from changesets c join users u on
c.user_id = u.id where c.id = 16425306; -- 0.09ms

-- total times are 15-19ms
-- or 15+0.09*137=27.33