package caqti

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package caqti
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Blocking API based on the Unix module.

This module implements a blocking API. It is not designed for preemptive threading. That is, connections and connection pools must be created and used within a single thread, and any limitation on multithreading from the driver or client library applies.

You can use a connection pool to cache a single DB connection, additional connections will not be allocated, since usage is serial.

module Stream : Caqti_stream_sig.S with type 'a fiber := 'a
module Pool : Caqti_pool_sig.S with type 'a fiber := 'a
module type CONNECTION = Caqti_connection_sig.S with type 'a fiber := 'a and type ('a, 'e) stream := ('a, 'e) Stream.t
include Caqti_connect_sig.S with type 'a fiber := 'a and type 'a with_switch := 'a and type 'a with_stdenv := 'a and type ('a, 'e) stream := ('a, 'e) Stream.t and type ('a, 'e) pool := ('a, 'e) Pool.t and type connection = (module CONNECTION)
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 ]) result

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) result) -> ('a, 'e) result

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.

val connect_pool : ?pool_config:Caqti_pool_config.t -> ?post_connect:(connection -> (unit, 'connect_error) result) -> ?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 ]) 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.

val or_fail : ('a, [< Caqti_error.t ]) result -> 'a

Takes Ok x to x and raises Caqti_error.Exn err on Error err.

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