ppx_rapper

Syntax extension for Caqti/PostgreSQL queries
Library ppx_rapper.runtime
Module type Rapper . Make_helper . CONNECTION
val driver_info : Caqti_driver_info.t

Information about the driver providing this connection module.

include Caqti_connection_sig.Base with type 'a future := 'a Io.t with type ('a, 'err) stream := ( 'a, 'err ) Stream.t

Query

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

call ~f request params performs request with parameters params invoking f to process the result. 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 Io.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 ] ) result Io.t

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

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

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

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

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

val disconnect : unit -> unit Io.t

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

val validate : unit -> bool Io.t

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

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

For internal use by Caqti_pool. 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 future := 'a Io.t

Retrieval Convenience

These are shortcuts for call combined with retrieval functions from Caqti_response_sig.S of the same name.

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

Combining call with Response.exec, this sends a request to the database and checks that no rows are returned.

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

Combining call with Response.exec and Response.affected_count, this sends a request to the database, checks that no rows are returned and returns the number of affected rows.

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

Combining call with Response.find, this sends a request to the database, checks that a single row is returned, and extracts it.

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

Combining call with Response.find_opt, this sends a request to the database, checks that at most one row is returned, and extracts it if present.

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

Combining call with Response.fold, this sends a request to the database and folds over the result rows.

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

Combining call with Response.fold_s, this sends a request to the database and folds sequentially over the result rows in a non-blocking manner.

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.

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

Combining call with Response.iter_s, this sends a request to the database and iterates sequentially over the result rows in a non-blocking manner. Please see the warning in fold_s about resource usage in the callback.

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

collect_list request param performs a call on request, extracting the result as a list.

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

rev_collect_list request param performs a call on request, extracting the result as a reversed list. This is more efficient than collect_list and fits well with a subsequent List.rev_map, though it may not matter much in practise.

Transactions

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

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

include Caqti_connection_sig.Populate with type 'a future := 'a Io.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 Io.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.