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(* netcgi_dbi.mli
Copyright (C) 2005-2006
Christophe Troestler
email: Christophe.Troestler@umh.ac.be
WWW: http://math.umh.ac.be/an/
This library is free software; see the file LICENSE for more information.
This library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the file
LICENSE for more details.
*)
(** Pools of connections for the ocamldbi generic database interface.
*)
module type DBI_DRIVER = sig
type connection
val connect : ?host:string -> ?port:string ->
?user:string -> ?password:string -> string ->
connection
val close : connection -> unit
val closed : connection -> bool
val commit : connection -> unit
val ping : connection -> bool
val rollback : connection -> unit
end
module type DBI_POOL = sig
type connection
val get : Netcgi.cgi -> ?host:string -> ?port:string ->
?user:string -> ?password:string -> string -> connection
(** Example: [module MyPool = DbiPool(Dbi_postgres)]
*
* [let dbh = MyPool.get request "database_name"]
*
* Returns an unused [Dbi.connection] handle from the pool of
* database handles. Or it may create a new database connection
* and return that.
*
* The parameters uniquely identify the database name
* (eg. "comments") and optional parameters. Separate pools are
* maintained for each combination of parameters.
*
* The connection is automatically returned to the pool at the
* end of the [cgi] request. After this time the connection may
* be given away to another user. For this reason, the calling
* code must NEVER stash the connection across requests
* (instead, call [get] to get a new handle each time).
*
* On returning the handle to the pool, the pool performs a
* ROLLBACK operation on the handle, thus losing any changes
* (INSERT, etc.) made to the database. If the program wants to
* preserve changes, it must perform a COMMIT operation itself,
* by calling [Dbi.connection.commit]. *)
end
module DbiPool(Dbi_driver : DBI_DRIVER) :
(DBI_POOL with type connection = Dbi_driver.connection)
(** [module MyPool = DbiPool (Dbi_postgres)]
*
* creates a pool of PostgreSQL database handles. To use them:
*
* [let dbh = MyPool.get r "database_name"]
*
* Gets you a new or recycled database handle [dbh] which is valid until
* the end of the current Apache request.
*)
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