Well I am using DB liberally so to be clear I am thinking there could be several possible data store formats that I deal with out the gate.
1. sqlite 2. mysql 3. postgresql 4. mongo 5. text fixed width 6. cvs I know it seems crazy but right now part of what I am dealing with is a lot of formats I have to pull data together from and I kind of figure my data module will allow me to save some conversion headaches. Also I am going to be playing with different DB's for benchmarking queries. The performance of a select query on an indexed field greatly impacts the success and usefulness of what I am dealing with. Basically I am trying to make the super swiss army of DB libraries specifically for my data. So I will know a lot about the nature of the data but may not know a lot about the medium that data is coming from. Probably an absurd plan, but for now I am still in the spit balling what is possible. Ken On Fri, Nov 11, 2016 at 01:22:50PM -0500, David Storrs wrote: > I think the first question is "what are you trying to achieve?" What > differences should the system demonstrate if it's hooked to MySQL vs > PostgreSQL? > > Personally, I just pass connection objects around. As long as you stick > with standard SQL this is all that's required to make your system work with > any DB. (Obviously, you need to avoid DB-specific extensions like > Postgres's incredibly convenient 'INSERT ... RETURNING <columns>' clause.) > > Here's an example: > > (define (dbh) > (postgresql-connect #:user "postgres" > #:database "dbname" > #:password "pass")) > > (define (placeholders-for lst [start-from 1]) > (string-join > (for/list ((i (in-naturals start-from)) > (ignored lst)) > (~a "$" i)) ;; returns, e.g. "$1,$2,$3" > ",")) > > (define (add-user username [db (dbh)]) > (query-exec > db > (format "INSERT INTO users (username) VALUES (~a)" > (placeholders-for (list username))) > username)) > > This is the bare bones for a completely engine-agnostic system. You could > add conditionals to dbh and placeholders-for so that they knew to generate > a MySQL handle and the string "?,?,?" instead of a Pg handle and > "$1,$2,$3" Then you can use add-user without caring what engine you're > attached to, just by passing in a connection object of the right type. > > > > > > > > > On Fri, Nov 11, 2016 at 9:39 AM, Ken MacKenzie <[email protected]> wrote: > > > I am trying to figure out the best way to do this and granted I am not > > sure my architecture is the most sane or sensible way to handle it. I am > > trying to build my DB interface and I want to allow the system to deal with > > numerous types of data stores. So I have a config file that is read and > > gets the information needed. So to pseudo lay it out: > > > > (define (query-db where-clause)) > > > > (define (db-type) > > (cond > > [(=? db-conf '(mysql)) (????)]) ;something to redefine how query-db > > actually works. > > ) > > > > Maybe this is silly as in query-db I can just do a conditional for each > > type. But then I have to do a conditional for each DB action, connect, > > drop, query, update, etc. I was thinking loading the conditional and > > redefining place holders would be a more elegant solution. I don't know > > just spit balling with a different design pattern here. > > > > Ken > > > > -- > > You received this message because you are subscribed to the Google Groups > > "Racket Users" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to [email protected]. > > For more options, visit https://groups.google.com/d/optout. > > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
