There's some valuable food for thought in this thread. My major problem with support various backends is the amount of work thats involved. Every single backend needs to play nice with all the primitives defined in Relational Algebra and that are implemented in ClojureQL. I believe that the SQL92 standard takes us very far down the middle road, but I realize that it wont take us all the way.
ClojureQL is actually two sets of primitives. Firstly its the RA stuf (select, project, join, etc) and then internally there is a number of primitives defined which help translate the RTable record into a query string. At the highest level only two functions need to be changed in order to effectively replace the entire compiler: to-sql and build- join. These call each other to build complex queries. If these were supplied as plugins, I think most backends could be fully supported simply by providing these two methods. They are not trivial however, so anybody interested in contributing should check out whats already there. Still thinking this through but the input is appreciated! Lau On Nov 25, 6:14 pm, rickmode <rickm...@gmail.com> wrote: > Allowing implementation-specific and optimized SQL only via strings > and not via a mechanism within ClojureQL allows its use in specific > applications but effectively prevents use for libraries and > frameworks. Indirect use of ClojureQL could yield unacceptable > performance with no elegant fix. > > On Nov 24, 11:28 pm, LauJensen <lau.jen...@bestinclass.dk> wrote: > > > Hi Brenton, > > > Yes the OFFSET/LIMIT syntax differs from backend to backend. However > > in some instances (like MySQL/PostgreSQL) they have ensured > > compatability so that the same statement will run on several DBs > > although the syntax might not be considered 'native'. For something > > like Oracle there actually isnt a syntax for LIMIT so instead they do > > something like > > > SELECT * FROM ( > > SELECT > > ROW_NUMBER() OVER (ORDER BY key ASC) AS rownumber, > > columns > > FROM tablename > > ) > > WHERE rownumber <= n > > > But as you can see it would be trivial to express this in terms of > > ClojureQL: > > > (defn oracle-take > > [tname limit] > > (-> (table (str "(SELECT ROW_NUMBER() OVER (ORDER BY key ASC)" > > " AS rownumber,columns" > > " FROM " (to-tablename tname) ")")) > > (select (where (<= :rownumber limit))) > > (project ["*"]))) > > > (to-sql (oracle-table :users 10)) > > ["SELECT * FROM (SELECT ROW_NUMBER() OVER (ORDER BY key ASC) AS > > rownumber,columns FROM users) WHERE (rownumber <= ?)" 10] > > > From the outset it has been my ambition to make ClojureQL extremely > > composable and as far as possible allow users to directly insert > > strings into the query to allow for backend specific customization. > > The entire design-plan of this customization is not yet thought out so > > input is welcomed. To me, flexibility and leaving with the power to > > the user is the key to wide adoption across various backends. > > > Lau > > > On Nov 24, 11:42 pm, Brenton <bashw...@gmail.com> wrote: > > > > > ClojureQL does not take the backend in to account. This is the one > > > > feature from the old CQL that I didn't want to carry over because it > > > > would be impossible for me to cater to all backends. If you hit > > > > specific problems, let me know and I'll see what we can do. > > > > > We adhere to SQL92 and test everything on MySQL and Postgres. If > > > > you're in a situation where thats not good enough, its always possible > > > > to supply part of your expression as a string. > > > > Lau > > > > Off the top of my head, I know that the LIMIT syntax for SQL Server is > > > totally different. A lot of the apps that I write end up getting > > > deployed using Oracle and SQL Server. If you plan for CQL to be widely > > > used I think you will need to take backends into account. You don't > > > need to implement them all yourself, but you should provide a way so > > > that others can implement them when they need to. > > > > Brenton -- 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
