Module Caqti_eio

Establishing Connections for Eio without Unix

This module provides connections to the PGX database for Eio applications. For other database systems, you will need Caqti_eio_unix.

The caqti-eio library should be considered unstable for now. Eio is in active development including its API, and the Caqti interface to it may benefit from further revision before the first major Eio release lands.

type stdenv = < net : [ `Generic ] Eio.Net.ty Eio.Std.r ; clock : float Eio.Time.clock_ty Eio.Std.r ; mono_clock : Eio.Time.Mono.ty Eio.Std.r >
module Stream : Caqti_stream_sig.S with type 'a fiber := 'a
module Pool : sig ... end
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 := sw:Eio.Switch.t -> 'a and type 'a with_stdenv := stdenv: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 module when passed as a value.

val connect : ?env:(Caqti_driver_info.t -> string -> Caqti_query.t) -> ?config:Caqti_connect_config.t -> ?tweaks_version:(int * int) -> sw:Eio.Switch.t -> stdenv:stdenv -> Uri.t -> (connection, [> Caqti_error.load_or_connect ]) Stdlib.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.

connect uri connects to the database at uri and returns a first class module implementing Caqti_connection_sig.S for the given database system. In case of preemptive threading, the connection must only be used from the thread where it was created.

The correct driver for the database system is inferred from the schema of uri; see the respective drivers for the supported schemas and related URI syntax. A driver can either be linked in to the application or, if supported, dynamically linked using the caqti-dynload package.

  • 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.

  • parameter config

    Configuration parameters related to the interaction with the database.

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

    Passed to connect.

  • parameter tweaks_version
val connect_pool : ?pool_config:Caqti_pool_config.t -> ?post_connect:(connection -> (unit, 'connect_error) Stdlib.result) -> ?env:(Caqti_driver_info.t -> string -> Caqti_query.t) -> ?config:Caqti_connect_config.t -> ?tweaks_version:(int * int) -> sw:Eio.Switch.t -> stdenv:stdenv -> 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 post_connect

    A task to run after establishing a new connection and before the connection becomes available to the application. This function can be used to customize to the database session.

  • parameter config

    Passed to connect when creating new connections.

  • parameter env

    Passed to connect when creating new connections.

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

Eliminates the error-case by raising Caqti_error.Exn.