# Functor Netcgi_dbi.DbiPool

    module DbiPool: functor (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.

Parameters: |
`Dbi_driver` | : | `DBI_DRIVER`

    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`.