Great. Congratulations.
How big is the latency in the FDW? This opens up new possibilities using redis. Very cool.On Wed, Jan 28, 2015 at 5:19 PM, Leon Dang <ldang@xxxxxxxxxxxxxx> wrote:
Andreas Kretschmer wrote on 01/28/2015 03:36 AM:
> I've implemented a completely new Redis FDW module which has little to do with
> github.com/pg-redis-fdw/redis_fdw; although I did take some inspiration from in
> on how the tables were to be designed but most I got from looking at the
> oracle-fdw.
>
> My redis-fdw implementation supports read and write to the Redis backend, so
> you can do insert, update, and delete. e.g. you can define a hash table as:
is it possible to write multiple row's into the redis? something like
insert into foreign_redis_table select * from big_table
Thanks for pointing this out. I had a small bug which didn't let it succeed, but now it's been fixed and committed; I've also added a bulkdata.sql test script in the code to show an example.
Anyway, thx, compiled and installed (just for fun, i'm not familiar with
redis, and i'm not a coder)
Redis is great for session management as it allows you to set an expiry for each key. So by using redis_fdw, you don't need to do multiple queries to determine of the session is still valid. e.g.:
-- use a string (key-value) dataset for user sessions
CREATE FOREIGN TABLE rsessions(
sessid TEXT,
value TEXT,
expiry INT
) SERVER localredis
OPTIONS (tabletype 'string');
ALTER FOREIGN TABLE rsessions ALTER COLUMN sessid OPTIONS (ADD param 'key');
-- a user table in postgres, can contain a whole bunch of other fields.
CREATE TEMP TABLE users (
userid INT,
username TEXT,
sessid TEXT
);
--
-- get user's details at the same time as determining if they're session is still valid
--
WITH u AS (SELECT * FROM users WHERE username = 'foo')
SELECT u.*, r.value, r.expiry
FROM rsessions r, u
WHERE r.sessid = (SELECT u.sessid FROM u);
If the user's session is still valid then a row will be returned (Redis automatically destroys the key on expiry).
--
-- to reset the expiry timeout for the user
--
UPDATE rsessions SET expiry = 40 WHERE sessid = $1;
Leon
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