Postgres work_mem tutorial

1. http://www.depesz.com/2011/07/03/understanding-postgresql-conf-work_mem/
2. http://dba.stackexchange.com/questions/27893/increasing-work-mem-and-shared-buffers-on-postgres-9-2-significantly-slows-down
3. http://dba.stackexchange.com/questions/41075/posgresql-setting-high-work-mem-does-not-avoid-disk-merge

SET ENABLE_SEQSCAN TO OFF;

show work_mem;
SET work_mem = '800MB';
query
RESET work_mem;
SET local work_mem = '800MB';