package caqti-lwt

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val driver_info : Caqti_driver_info.t

Information about the driver providing this connection module.

val driver_connection : Caqti_connection_sig.driver_connection option

The underlying connection object of the driver if available. The open variant constructor is defined in the driver library. This is currently only implemented for caqti-driver-sqlite3 for the purpose of defining custom functions.

include Caqti_connection_sig.Base with type 'a fiber := 'a Lwt.t with type ('a, 'e) stream := ('a, 'e) Stream.t

Query

module Response : Caqti_response_sig.S with type 'a fiber := 'a Lwt.t and type ('a, 'err) stream := ('a, 'err) Stream.t
val call : f:(('b, 'm) Response.t -> ('c, 'e) Stdlib.result Lwt.t) -> ('a, 'b, 'm) Caqti_request.t -> 'a -> ('c, [> Caqti_error.call ] as 'e) Stdlib.result Lwt.t

call ~f request params executes request with parameters params invoking f to process the result; except the driver may postpone the request until f attempts to retrieve the result.

One of the result retrieval functions must be called exactly once before f returns a non-error result. If a result retrieval function is not called, it is unspecified whether the database query has been issued.

The argument of f is only valid during the call to f, and must not be returned or operated on by other threads.

val set_statement_timeout : float option -> (unit, [> Caqti_error.call ]) Stdlib.result Lwt.t

Set or clear the timeout after which a running SQL statement will be terminated if supported by the driver. This is currently supported for MariaDB (using max_statement_time) and PostgreSQL (using statement_timeout) and has no effect for SQLite3.

Transactions

val start : unit -> (unit, [> Caqti_error.transact ]) Stdlib.result Lwt.t

Starts a transaction if supported by the underlying database, otherwise does nothing.

val commit : unit -> (unit, [> Caqti_error.transact ]) Stdlib.result Lwt.t

Commits the current transaction if supported by the underlying database, otherwise does nothing.

val rollback : unit -> (unit, [> Caqti_error.transact ]) Stdlib.result Lwt.t

Rolls back a transaction if supported by the underlying database, otherwise does nothing.

Disconnection and Reuse

val deallocate : ('a, 'b, 'm) Caqti_request.t -> (unit, [> Caqti_error.call ]) Stdlib.result Lwt.t

deallocate req deallocates the prepared query for req if it was allocated. The request must not be oneshot.

val disconnect : unit -> unit Lwt.t

Calling disconnect () closes the connection to the database and frees up related resources.

val validate : unit -> bool Lwt.t

For internal use by pool implementations. Tries to ensure the validity of the connection and must return false if unsuccessful.

val check : (bool -> unit) -> unit

For internal use by pool implementations. Called after a connection has been used. check f must call f () exactly once with an argument indicating whether to keep the connection in the pool or discard it.

include Caqti_connection_sig.Convenience with type 'a fiber := 'a Lwt.t

Retrieval Convenience

Each of these shortcuts combine call with the correspondingly named retrieval function from Caqti_response_sig.S.

val exec : ('a, unit, [< `Zero ]) Caqti_request.t -> 'a -> (unit, [> Caqti_error.call_or_retrieve ] as 'e) Stdlib.result Lwt.t

exec req x performs req with parameters x and checks that no rows are returned. See also Caqti_response_sig.S.exec.

val exec_with_affected_count : ('a, unit, [< `Zero ]) Caqti_request.t -> 'a -> (int, [> Caqti_error.call_or_retrieve | `Unsupported ] as 'e) Stdlib.result Lwt.t

exec_with_affected_count req x performs req with parameters x, checks that no rows are returned, and returns the number of affected rows.

See also Caqti_response_sig.S.exec and Caqti_response_sig.S.affected_count.

val find : ('a, 'b, [< `One ]) Caqti_request.t -> 'a -> ('b, [> Caqti_error.call_or_retrieve ] as 'e) Stdlib.result Lwt.t

find req x performs req with parameters x, checks that a single row is retured, and returns it.

See also Caqti_response_sig.S.find.

val find_opt : ('a, 'b, [< `Zero | `One ]) Caqti_request.t -> 'a -> ('b option, [> Caqti_error.call_or_retrieve ] as 'e) Stdlib.result Lwt.t

find_opt req x performs req with parameters x and returns either None if no rows are returned or Some y if a single now y is returned and fails otherwise.

See also Caqti_response_sig.S.find_opt.

val fold : ('a, 'b, [< `Zero | `One | `Many ]) Caqti_request.t -> ('b -> 'c -> 'c) -> 'a -> 'c -> ('c, [> Caqti_error.call_or_retrieve ] as 'e) Stdlib.result Lwt.t

fold req f x acc performs req with parameters x and passes acc through the composition of f y across the result rows y in the order of retrieval.

See also Caqti_response_sig.S.fold.

val fold_s : ('a, 'b, [< `Zero | `One | `Many ]) Caqti_request.t -> ('b -> 'c -> ('c, 'e) Stdlib.result Lwt.t) -> 'a -> 'c -> ('c, [> Caqti_error.call_or_retrieve ] as 'e) Stdlib.result Lwt.t

fold_s f x acc performs req with parameters x and passes acc through the monadic composition of f y across the returned rows y in the order of retrieval.

Please be aware of possible deadlocks when using resources from the callback. In particular, if the same connection pool is invoked as the one used to obtain the current connection, it will deadlock if the pool has just run out of connections. An alternative is to collect the rows first e.g. with fold and do the nested queries after exiting.

See also Caqti_response_sig.S.fold_s.

val iter_s : ('a, 'b, [< `Zero | `One | `Many ]) Caqti_request.t -> ('b -> (unit, 'e) Stdlib.result Lwt.t) -> 'a -> (unit, [> Caqti_error.call_or_retrieve ] as 'e) Stdlib.result Lwt.t

iter_s f x performs req with parameters x and sequences calls to f y for each result row y in the order of retrieval.

Please see the warning in fold_s about resource usage in the callback.

See also Caqti_response_sig.S.iter_s.

val collect_list : ('a, 'b, [< `Zero | `One | `Many ]) Caqti_request.t -> 'a -> ('b list, [> Caqti_error.call_or_retrieve ] as 'e) Stdlib.result Lwt.t

collect_list request x performs a req with parameters x and returns a list of rows in order of retrieval. The accumulation is tail recursive but slightly less efficient than rev_collect_list.

val rev_collect_list : ('a, 'b, [< `Zero | `One | `Many ]) Caqti_request.t -> 'a -> ('b list, [> Caqti_error.call_or_retrieve ] as 'e) Stdlib.result Lwt.t

rev_collect_list request x performs request with parameters x and returns a list of rows in the reverse order of retrieval. The accumulation is tail recursive and slighly more efficient than collect_list.

Transactions

val with_transaction : (unit -> ('a, 'e) Stdlib.result Lwt.t) -> ('a, [> Caqti_error.transact ] as 'e) Stdlib.result Lwt.t

with_transaction f wraps f in a transaction which is committed iff f returns Ok _.

include Caqti_connection_sig.Populate with type 'a fiber := 'a Lwt.t and type ('a, 'err) stream := ('a, 'err) Stream.t

Insertion

val populate : table:string -> columns:string list -> 'a Caqti_type.t -> ('a, 'err) Stream.t -> (unit, [> Caqti_error.call_or_retrieve | `Congested of 'err ]) Stdlib.result Lwt.t

populate table columns row_type seq inputs the contents of seq into the database in whatever manner is most efficient as decided by the driver.