caqti 1.9.0 · OCaml Package

Constructs the main module used to connect to a database for the given concurrency model.

Parameters

module System : Caqti_driver_sig.System_unix

Signature

module Pool : Caqti_pool_sig.S with type 'a future := 'a System.future

A pool implementation for the current concurrency library.

module Stream = System.Stream

module type CONNECTION =
  Caqti_connection_sig.S
    with type 'a future := 'a System.future
     and type ('a, 'err) stream := ('a, 'err) Stream.t

The connection API specialized for the current concurrency library.

type connection = (module CONNECTION)

Shortcut for the connection API passed as a value.

val connect : 
  ?env:(Caqti_driver_info.t -> string -> Caqti_query.t) ->
  ?tweaks_version:(int * int) ->
  Uri.t ->
  (connection, [> Caqti_error.load_or_connect ]) Stdlib.result System.future

connect uri locates and loads a driver which can handle uri, passes uri to the driver, which establish a connection and returns a first-class module implementing Caqti_connection_sig.S.

If you use preemptive threading, note that the connection must only be used from the thread where it was created.

See Database Tweaks for details about the tweaks_version parameter.

parameter tweaks_version
Declares compatibility with database tweaks introduced up to the given version of Caqti. Defaults to a conservative value. See the above reference for more info (not linked here due to odoc issue).

parameter env
If provided, this function will do a final expansion of environment variables which occurs in the query templates of the requests executed on the connection.

val with_connection : 
  ?env:(Caqti_driver_info.t -> string -> Caqti_query.t) ->
  ?tweaks_version:(int * int) ->
  Uri.t ->
  (connection ->
    ('a, [> Caqti_error.load_or_connect ] as 'e) Stdlib.result System.future) ->
  ('a, 'e) Stdlib.result System.future

with_connection uri f calls connect on uri. If connect evaluates to Ok connection, with_connection passes the connection to f. Once f either evaluates to a result, or raises an exception, with_connection closes the database connection.

parameter tweaks_version
Passed to connect.

parameter env
Passed to connect.

val connect_pool : 
  ?max_size:int ->
  ?max_idle_size:int ->
  ?max_use_count:int option ->
  ?post_connect:
    (connection -> (unit, 'connect_error) Stdlib.result System.future) ->
  ?env:(Caqti_driver_info.t -> string -> Caqti_query.t) ->
  ?tweaks_version:(int * int) ->
  Uri.t ->
  ((connection, [> Caqti_error.connect ] as 'connect_error) Pool.t,
    [> Caqti_error.load ])
    Stdlib.result

connect_pool uri is a pool of database connections constructed by connect uri.

Do not use pooling for connections to volatile resources like sqlite3::memory: and beware of temporary tables or other objects which may not be shared across connections to the same URI.

If you use preemptive threading, note that the connection pool must only be used from the thread where it was created. Use thread local storage to create a separate pool per thread if necessary.

parameter tweaks_version
Passed to connect when creating new connections.

parameter env
Passed to connect when creating new connections.

parameter max_size
The maximum number of open connections. Must be at least 1. For drivers which does not support concurrent connections, this will be ignored and the value 1 used instead.

parameter max_idle_size
The maximum number of idle connections to put into the pool for reuse. Defaults to max_size. Must be between 0 and max_size. If you set this, you must also set max_size. For drivers which does not support pooling, this will be ignored and the value 0 used instead. For drivers which does not support concurrent connections, but supports pooling, the value will clipped to a maximum of 1.

parameter max_use_count
The maximum number of times to use a connection before dropping it from the pool, or None for no limit. The default is currently 100, but may be changed in the future based on real-world experience. The reason this setting was introduced is that we have seen state being retained on the server side.

package caqti

Parameters

Signature