Performance wise the conclusion is batch queries done this way are around 60% faster than doing separate queries for even very simple queries.
On Monday, November 9, 2015 at 11:45:48 AM UTC+1, Niels van Klaveren wrote: > > While answering this question > <http://stackoverflow.com/questions/33600132/checking-if-uuid-exists-in-postgresql-table-using-clojure-java-jdbc-db-do-prepar/33605673#33605673> > > 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.