armollica

k-d tree nearest neighbors search (k-NN). The red dots are the 10 nearest neighbors. Orange dots are scanned and not selected.

Compare with this block that implements a k nearest neighbor search using a quadtree instead of a k-d tree.

The algorithm for this search came from this course handout. Note that the "k" in k-d tree need not be the same number as the "k" in

rgreenjr

-- show running queries (pre 9.2)
SELECT procpid, age(clock_timestamp(), query_start), usename, current_query 
FROM pg_stat_activity 
WHERE current_query != '<IDLE>' AND current_query NOT ILIKE '%pg_stat_activity%' 
ORDER BY query_start desc;

-- show running queries (9.2)
SELECT pid, age(clock_timestamp(), query_start), usename, query 
FROM pg_stat_activity 
WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%'