On Tue, Aug 27, 2019 at 3:47 AM ROS Didier <didier.ros@edf.fr> wrote:
Hi
In my business, one of the things blocking the migration from Oracle to PostgreSQL is not having the equivalent of Oracle Real Application Testing .
This product captures a charge in production and replay it in a test environment.
this allows to know the impacts of a migration to a newer version, the creation of an index..
is there an equivalent in the PostgreSQL community?
if not, do you think it's technically possible to do it ?
who would be interested in this project ?
Replaying workload might or might not apply well to your case.
There are several major difficulties if you want to replay workload:
1) How to "record" workload. You need to write all your queries to the Postgres log. Three problems here:
1a) pgreplay expects log_statements = 'all' while you might prefer dealing with log_min_duration_statement instead. This is a minor issue though, quite easy to solve with preprocessing.
1b) under heavy load, log_min_duration_statement = 0 (or log_statements = 'all') will lead to performance degradation or even downtime. Possible solutions are: write to memory, or don't write at all but send over the network.
1c) ideally, recoding just queries is not enough. To replay workload "as is", we need to replay queries with known plans. There is no easy solution to this problem in the Postgres ecosystem yet.
why? i prefer queries to take advantage of new plans for example if i'm migrating from 9.5 to 9.6+ i would prefer that, when replaying, the queries use parallel plans so i quickly get if that would somehow be a problem (for example by using more cpu than before)