Re: what's the slowest part in the SQL

Not really, the server has 2 GB memory (PROD is a lot more than this dev box), so the table should be able to fit in memory if we preload them.

MemTotal: 2049572 kB

dev=# select pg_size_pretty(pg_relation_size('data'));
pg_size_pretty
----------------
141 MB
(1 row)

Time: 2.640 ms

dev=# select pg_size_pretty(pg_relation_size('order'));
pg_size_pretty
----------------
516 MB
(1 row)

Thanks,
Suya
On 8/10/16, 11:57 AM, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

Suya Huang <shuang(at)connexity(dot)com> writes:
> Thank you Tom very much, that’s the piece of information I miss.
> So, should I expect that the nested loop join would be much faster if I cache both tables (use pg_prewarm) into memory as it waives the disk read?

pg_prewarm is not going to magically fix things if your table is bigger
than RAM, which it apparently is.

regards, tom lane