Hello Clojurians,
I found passing around the database connection to each function that uses
it very error prone when you are using transactions as passing the wrong
one could mean a query runs outside the transaction when in the source code
it is inside the with-db-transaction function. So I ended up defining the
db namespace like this:
(ns db)
(defonce ^:dynamic conn (atom nil))
(defn connect!
(reset conn (generate-new-connection)))
(defn run-query
[query] (run-query query @conn)
[query conn] (run-the-query-in-connection query conn))
This is pseudo-code of course, simplified to highlight the part that I'm
most unfamiliar with:
(defonce ^:dynamic conn (atom nil))
The reason why it's an atom is so that connect! can *set* it and the reason
why it's a dynamic var is so I can do this:
(jdbc/with-db-transaction
[db-connection-with-transaction @db/conn]
(binding [db/conn (atom db-connection-with-transaction)]
(db/run-query "SELECT *"))))))
and the query will be implicitly run inside the transaction. Does it make
sense? Is this wrong? will it fail in unexpected ways? Is there a better
way?
Thanks.
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