Up  

Module PGOCaml


module PGOCaml: sig .. end
Database handle.
type 'a t
Database handle.
exception Error of string
For library errors.
exception PostgreSQL_Error of string * (char * string) list
For errors generated by the PostgreSQL database back-end. The first argument is a printable error message. The second argument is the complete set of error fields returned from the back-end. See http://www.postgresql.org/docs/8.1/static/protocol-error-fields.html

Connection management

val connect : ?host:string ->
       ?port:int ->
       ?user:string ->
       ?password:string ->
       ?database:string -> ?unix_domain_socket_dir:string -> unit -> 'a t
Connect to the database. The normal $PGDATABASE, etc. environment variables are available.
val close : 'a t -> unit
Close the database handle. You must call this after you have finished with the handle, or else you will get leaked file descriptors.
val ping : 'a t -> unit
Ping the database. If the database is not available, some sort of exception will be thrown.

Transactions

val begin_work : 'a t -> unit
Start a transaction.
val commit : 'a t -> unit
Perform a COMMIT operation on the database.
val rollback : 'a t -> unit
Perform a ROLLBACK operation on the database.

Serial column

val serial : 'a t -> string -> int64
This is a shorthand for SELECT CURRVAL(serial). For a table called table with serial column id you would typically call this as serial dbh "table_id_seq" after the previous INSERT operation to get the serial number of the inserted row.
val serial4 : 'a t -> string -> int32
As PGOCaml.serial but assumes that the column is a SERIAL or SERIAL4 type.
val serial8 : 'a t -> string -> int64
Same as PGOCaml.serial.

Miscellaneous

val max_message_length : int Pervasives.ref
Maximum message length accepted from the back-end. The default is Sys.max_string_length, which means that we will try to read as much data from the back-end as we can, and this may cause us to run out of memory (particularly on 64 bit machines), causing a possible denial of service. You may want to set this to a smaller size to avoid this happening.
val verbose : int Pervasives.ref
Verbosity. 0 means don't print anything. 1 means print short error messages as returned from the back-end. 2 means print all messages as returned from the back-end. Messages are printed on stderr. Default verbosity level is 1.
val set_private_data : 'a t -> 'a -> unit
Attach some private data to the database handle.

NB. The pa_pgsql camlp4 extension uses this for its own purposes, which means that in most programs you will not be able to attach private data to the database handle.

val private_data : 'a t -> 'a
Retrieve some private data previously attached to the database handle. If no data has been attached, raises Not_found.

NB. The pa_pgsql camlp4 extension uses this for its own purposes, which means that in most programs you will not be able to attach private data to the database handle.

type pa_pg_data = (string, bool) Hashtbl.t
When using pa_pgsql, database handles have type PGOCaml.pa_pg_data PGOCaml.t

Low level query interface - DO NOT USE DIRECTLY

type oid = int32 
type param = string option
None is NULL.
type result = string option
None is NULL.
type row = result list
One row is a list of fields.
val prepare : 'a t ->
       query:string -> ?name:string -> ?types:oid list -> unit -> unit
prepare conn ~query ?name ?types () prepares the statement query and optionally names it name and sets the parameter types to types. If no name is given, then the "unnamed" statement is overwritten. If no types are given, then the PostgreSQL engine infers types. Synchronously checks for errors.
val execute : 'a t ->
       ?name:string ->
       ?portal:string -> params:param list -> unit -> row list
execute conn ?name ~params () executes the named or unnamed statement name, with the given parameters params, returning the result rows (if any).

There are several steps involved at the protocol layer: (1) a "portal" is created from the statement, binding the parameters in the statement (Bind). (2) the portal is executed (Execute). (3) we synchronise the connection (Sync).

The optional ?portal parameter may be used to name the portal created in step (1) above (otherwise the unnamed portal is used). This is only important if you want to call PGOCaml.describe_portal to find out the result types.

val close_statement : 'a t -> ?name:string -> unit -> unit
close_statement conn ?name () closes a prepared statement and frees up any resources.
val close_portal : 'a t -> ?portal:string -> unit -> unit
close_portal conn ?portal () closes a portal and frees up any resources.
type row_description = result_description list

type result_description = {
   name : string; (*Field name.*)
   table : oid option; (*OID of table.*)
   column : int option; (*Column number of field in table.*)
   field_type : oid; (*The type of the field.*)
   length : int; (*Length of the field.*)
   modifier : int32; (*Type modifier.*)
} 
type params_description = param_description list

type param_description = {
   param_type : oid; (*The type of the parameter.*)
} 
val describe_statement : 'a t ->
       ?name:string ->
       unit -> params_description * row_description option
describe_statement conn ?name () describes the named or unnamed statement's parameter types and result types.
val describe_portal : 'a t -> ?portal:string -> unit -> row_description option
describe_portal conn ?portal () describes the named or unnamed portal's result types.

Low level type conversion functions - DO NOT USE DIRECTLY

val name_of_type : ?modifier:int32 -> oid -> string
Returns the OCaml equivalent type name to the PostgreSQL type oid. For instance, name_of_type (Int32.of_int 23) returns "int32" because the OID for PostgreSQL's internal int4 type is 23. As another example, name_of_type (Int32.of_int 25) returns "string".
type timestamptz = Calendar.t * Time_Zone.t 
type int16 = int 
type bytea = string 
type int32_array = int32 array 
val string_of_oid : oid -> string
val string_of_bool : bool -> string
val string_of_int : int -> string
val string_of_int16 : int16 -> string
val string_of_int32 : int32 -> string
val string_of_int64 : int64 -> string
val string_of_float : float -> string
val string_of_timestamp : Calendar.t -> string
val string_of_timestamptz : timestamptz -> string
val string_of_date : Date.t -> string
val string_of_time : Time.t -> string
val string_of_interval : Calendar.Period.t -> string
val string_of_int32_array : int32_array -> string
val string_of_bytea : bytea -> string
val string_of_string : string -> string
val string_of_unit : unit -> string
val bool_of_string : string -> bool
val int_of_string : string -> int
val int16_of_string : string -> int16
val int32_of_string : string -> int32
val int64_of_string : string -> int64
val float_of_string : string -> float
val timestamp_of_string : string -> Calendar.t
val timestamptz_of_string : string -> timestamptz
val date_of_string : string -> Date.t
val time_of_string : string -> Time.t
val interval_of_string : string -> Calendar.Period.t
val int32_array_of_string : string -> int32_array
val bytea_of_string : string -> bytea
val unit_of_string : string -> unit
These conversion functions are used by pa_pgsql to convert values in and out of the database.