Class virtual Dbi.connection

class virtual connection : ?host:string ->
       ?port:string -> ?user:string -> ?password:string -> string -> object  end

Connection managment & information

method id : int

Returns a unique integer which can be used to identify this connection.

method close : unit -> unit

Closes the database handle. All statement handles are also invalidated. Database handles which are collected by the GC are automatically closed, but you should explicitly close handles to save resources, where possible.

method closed : bool

Returns true if this database handle has been closed. Subsequent operations on the handle will fail.

method ping : unit -> bool

This uses some active method to verify that the database handle is still working. By this I mean that it tries to execute some sort of 'null' statement against the database to see if it gets a response. If the database is up, it returns true. If the database is down or unresponsive, it returns false. This method should never throw an exception (unless, perhaps, there is some sort of catastrophic internal error in the Dbi library or the driver).

method host : string option

Return the host parameter.

method port : string option

Return the port parameter.

method user : string option

Return the user parameter.

method password : string option

Return the password parameter.

method database : string

Return the database name.

method virtual database_type : string

Database type (e.g. "postgres").

method set_debug : bool -> unit

Use this to enable debugging on the handle. In this mode significant events (such as executing queries) are printed out on stderr.

method debug : bool

Returns true if this handle has debugging enabled.

Database creation, destruction & connection

Statement preparation

method virtual prepare : string -> statement

Prepare a database query, and return the prepared statement. The statement may contain ? placeholders which can be substituted for values when the statement is executed.

method prepare_cached : string -> statement

This method is identical to prepare except that, if possible, it caches the statement handle with the database object. Future calls with the same query string return the previously prepared statement. For databases which support prepared statement handles, this avoids a round-trip to the database, and an expensive recompilation of the statement.

method ex : string -> sql_t list -> statement

dbh#ex stm args is a shorthand for

 let sth = dbh#prepare_cached stmt in

 sth#execute args;

 sth

Commit and rollback

method commit : unit -> unit

Perform a COMMIT operation on the database.

method rollback : unit -> unit

Perform a ROLLBACK operation on the database.

method register_precommit : (unit -> unit) -> precommit_handle

Register a function which will be called just BEFORE a commit happens on this handle. This method returns a handle which can be used to deregister the callback later. This is useful for implementing various types of persistence.

method unregister_precommit : precommit_handle -> unit

Unregister a precommit callback.

method register_postrollback : (unit -> unit) -> postrollback_handle

Register a function which will be called just AFTER a rollback happens on this handle. This method returns a handle which can be used to deregister the callback later. This is useful for implementing various types of persistence.

method unregister_postrollback : postrollback_handle -> unit

Unregister a postrollback callback.