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package caqti-async
val driver_info : Caqti_driver_info.tInformation about the driver providing this connection module.
val driver_connection : Caqti_connection_sig.driver_connection optionThe 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 Async_kernel.Deferred.t
with type ('a, 'e) stream := ('a, 'e) Stream.t
Query
module Response :
Caqti_response_sig.S
with type 'a fiber := 'a Async_kernel.Deferred.t
and type ('a, 'err) stream := ('a, 'err) Stream.tval call :
f:(('b, 'm) Response.t -> ('c, 'e) result Async_kernel.Deferred.t) ->
('a, 'b, 'm) Caqti_request.t ->
'a ->
('c, [> Caqti_error.call ] as 'e) result Async_kernel.Deferred.tcall ~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 ]) result Async_kernel.Deferred.tSet 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 ]) result Async_kernel.Deferred.tStarts a transaction if supported by the underlying database, otherwise does nothing.
val commit :
unit ->
(unit, [> Caqti_error.transact ]) result Async_kernel.Deferred.tCommits the current transaction if supported by the underlying database, otherwise does nothing.
val rollback :
unit ->
(unit, [> Caqti_error.transact ]) result Async_kernel.Deferred.tRolls 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 ]) result Async_kernel.Deferred.tdeallocate req deallocates the prepared query for req if it was allocated. The request must not be oneshot.
val disconnect : unit -> unit Async_kernel.Deferred.tCalling disconnect () closes the connection to the database and frees up related resources.
val validate : unit -> bool Async_kernel.Deferred.tFor internal use by pool implementations. Tries to ensure the validity of the connection and must return false if unsuccessful.
include Caqti_connection_sig.Convenience
with type 'a fiber := 'a Async_kernel.Deferred.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) result
Async_kernel.Deferred.texec 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) result
Async_kernel.Deferred.texec_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) result Async_kernel.Deferred.tfind 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) result
Async_kernel.Deferred.tfind_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) result Async_kernel.Deferred.tfold 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) result Async_kernel.Deferred.t) ->
'a ->
'c ->
('c, [> Caqti_error.call_or_retrieve ] as 'e) result Async_kernel.Deferred.tfold_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) result Async_kernel.Deferred.t) ->
'a ->
(unit, [> Caqti_error.call_or_retrieve ] as 'e) result
Async_kernel.Deferred.titer_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) result
Async_kernel.Deferred.tcollect_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) result
Async_kernel.Deferred.trev_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) result Async_kernel.Deferred.t) ->
('a, [> Caqti_error.transact ] as 'e) result Async_kernel.Deferred.twith_transaction f wraps f in a transaction which is committed iff f returns Ok _.
include Caqti_connection_sig.Populate
with type 'a fiber := 'a Async_kernel.Deferred.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 ]) result
Async_kernel.Deferred.tpopulate table columns row_type seq inputs the contents of seq into the database in whatever manner is most efficient as decided by the driver.