> In my case config/db is really read from a config.edn file and may point
> to a mysql, postgresql or sqlite database.
Then you can add a :streaming-options key to your EDN file and do this in your
code:
(into [] (take 2) (jdbc/reducible-query config/db (:streaming-options
config/db)))
As Luke said, it’s not java.jdbc’s job to support a concept like “streaming”
when that requires different options on every database – java.jdbc’s job is to
let users provide all the options they need and make sure they’re delivered to
the appropriate parts of the JDBC driver, connection, statement, transaction,
etc.
A comment on your use of EDN to produce a db-spec: for production code I’d
strongly recommend using a connection pool instead of just a bare hash map
db-spec in every call, otherwise you’re going to pay the cost of setting up and
tearing down a full DB connection for every operation!
The :auto-commit? option is supported in 0.7.0-beta5 which should hit Maven
Central by tomorrow (or maybe late tonight). Please let me know if it solves
the streaming problem.
Sean Corfield -- (970) FOR-SEAN -- (904) 302-SEAN
An Architect's View -- http://corfield.org/
"If you're not annoying somebody, you're not really alive."
-- Margaret Atwood
From: Ralf Schmitt
Sent: Wednesday, July 5, 2017 2:57 PM
To: Sean Corfield; Clojure Mailing List
Subject: Re: JDBC Connection auto-commit?: [ANN] clojure.java.jdbc 0.7.0 Beta1
Sean Corfield <s...@corfield.org> writes:
> Rather than doing something that requires a dependency on specific JDBC
> driver classes, it seems that if an :auto-commit option in the db-spec were
> honored by get-connection you would get what you needed:
>
> (into [] (take 2) (jdbc/reducible-query (assoc config/db :auto-commit
> false) query {:fetch-size 500}))
>
> You can already pass additional options into the DriverManager/getConnection
> call as properties (from the db-spec) but autocommit does not appear to be
> supported in that format.
>
> Actually, it would be cleaner if get-connection had a 2-arity accepting
> db-spec and opts, and then everything could pass opts into get-connection and
> you could do:
>
> (into [] (take 2) (jdbc/reducible-query config/db query {:fetch-size
> 500 :auto-commit false }))
That would work, but I have to look at which database driver is being
used here when creating the reducible-query. I would have to pass the
right options depending on the database driver being used instead of
passing a {:use-streaming? true} as options.
In my case config/db is really read from a config.edn file and may point
to a mysql, postgresql or sqlite database.
The extend-protocol form would be provided by the user's code, not by
java.jdbc, so there's no dependency on a specific JDBC driver class.
Anyway I could live with both solutions. And I'm aware of the fact that
an additional protocol to turn on streaming also introduces additional
complexity.
Being able to pass the :auto-commit option would already be a nice
improvement since I could get rid of the outer jdbc/with-db-connection.
I hope I've made my point clear. I'm going to trust your best judgement
on this issue from now on.
Thanks again for your work on java.jdbc.
--
Cheers
Ralf
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