On Fri, Mar 9, 2012 at 5:24 AM, Fujii Masao <masao.fu...@gmail.com> wrote: > When a relation is loaded into cache, are corresponding indexes also loaded > at the same time?
No, although if you wanted to do that you could easily do so, using a query like this: select pg_prewarm(indexrelid, 'main', 'read', NULL, NULL) from pg_index where indrelid = 'your_table_name'::regclass; > Can this load only the specified index into cache? Yes. The relation can be anything that has storage, so you can prewarm either a table or an index (or even a sequence or TOAST table, if you're so inclined). > When the relation is too huge to fit into the cache and most access pattern > in the system is index scan, DBA might want to load only index rather > than table. > For such system, so far I've been suggesting using pgstatindex, but it's good > if pg_prewarm can do that pgstatindex is an interesting idea; hadn't thought of that. Actually, though, pgstaindex probably ought to be using a BufferAccessStrategy to avoid trashing the cache. I've had reports of pgstatindex torpedoing performance on production systems. > This utility might be helpful to accelerate a recovery of WAL record not > containing FPW. IOW, before starting a recovery, list the relations to recover > from WAL files by using xlogdump tool, load them into cache by using > this utility, > and then start a recovery. Interesting idea. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
