Niels van Klaveren wrote on Monday, November 9, 2015 at 7:20 AM: OK, so after some more experimentation I found out I needed to do the get-connection in the prepare-statement instead of the with-db-connection binding. A bit counter-intuitive, and I hope it will still work when a connection pool is used.
Yes, with-db-connection gives you a db-spec with a DB connection added which is specifically what let’s you use get-connection on it to retrieve the existing connection. Prepare-statement accepts a connection, not a db-spec. Suggestions to improve docstrings are welcomed, as are Pull Requests to improve the community-maintained documentation here: http://clojure-doc.org/articles/ecosystem/java_jdbc/home.html Sean (j/with-db-connection [c datasource] (let [ps (j/prepare-statement (j/get-connection c) "SELECT count(*) from person where left(name,1)=?")] (doall (map #(j/query c [ps %]) ["a" "b" "c" "d" "e" "f"])))) On Monday, November 9, 2015 at 11:45:48 AM UTC+1, Niels van Klaveren wrote: While answering this question on stackoverflow about do-prepared I wanted to show the way to do multiple queries with the same prepared statement (batch select). I thought this is possible in Java, but in clojure.java.sql I ran into several problems. Granted that given a properly parameterized query the database should be able to optimize this automatically by using the execution plan from the cache, it might give an extra bit of performance by stating it up front. So I set out to test if that was true, but without much success Here's my first attempt: (j/with-db-connection[c datasource] (let [ps (j/prepare-statement c "SELECT count(*) from person where left(name,1)=?")] (doall (map #(j/query c [ps %]) ["a" "b"])))) ClassCastException clojure.lang.PersistentHashMap cannot be cast to java.sql.Connection clojure.java.jdbc/prepare-statement (jdbc.clj:454) This is because prepare-statement seems to expect a true connection, not the datasource map. All other attempts to wrangle a connection into with-db-connection ended up in other errors. (j/with-db-transaction [c (j/get-connection datasource)] (let [ps (j/prepare-statement c "SELECT count(*) from person where left(name,1)=?")] (doall (map #(j/query c [ps %]) ["a" "b"])))) IllegalArgumentException No implementation of method: :get-level of protocol: #'clojure.java.jdbc/Connectable found for class: com.microsoft.sqlserver.jdbc.SQLServerConnection clojure.core/-cache-protocol-fn (core_deftype.clj:544) Since query accepts a prepared statement instead of a string, I thought this should be possible without having to implement a query equivalent of do-prepared. Is there something I overlooked ? -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
