Clojure.java.jdbc基于查询结构返回日期时间更改的类型

Question

I have a Korma based software stack that constructs fairly complex queries against a MySQL database. I noticed that when I am querying for datetime columns, the type that I get back from the Korma query changes depending on the syntax of the SQL query being generated. I've traced this down to the level of clojure.java.jdbc/query. If the form of the query is like this:

select modified from docs order by modified desc limit 10

then I get back maps corresponding to each database row in which :modified is a java.sql.Timestamp . However, sometimes our query generator generates more complex union queries, such that we need to apply an order by ... limit ... constraint to the final result of the union. Korma does this by wrapping the query in parentheses. Even with only a single subquery--ie, a simple parenthesized select--so long as we add an "outer" order by ... , the type of :modified changes.

(select modified from docs order by modified desc limit 10) order by modified desc

In this case, clojure.java.jdbc/query returns :modified values as strings. Some of our higher level code isn't expecting this, and gets exceptions.

We're using a fork of Korma, which is using an old (0.3.7) version of clojure.java.jdbc . I can't tell if the culprit is clojure.java.jdbc or java.jdbc or MySQL. Anyone seen this and have ideas on how to fix it?

Answer 1

Moving to the latest jdbc in a similar situation changed several other things for us and was a decidedly "non-trvial" task. I would suggest getting off of a korma fork soon and then debugging this.

For us the changes focused around what korma returned on update calls changed between the verions of the backing jdbc. It was well worth getting current even though it's a moderately painful process.

Getting current with jdbc will give you fresh new problems! best of luck with this :-) These things tend to be fairly specific to the DB server you are using.

Other options for you is to have a policy of aways specifying an order-by parameter or building a library to coerce the strings into dates. Both of these have some long term technical dept problems.