Type descriptors for fields and tuples.
The following is normally only needed for drivers and to define new field types. Everything needed for common usage is covered in Row Types.
An extensible type describing primitive SQL types and types which can be converted to and from such types. When adding a new constructor, register the coding with Field.define_coding if possible. Otherwise, the type will only work with drivers which handle it themselves. The shipped drivers only handle the constructors listed here.
type field += Primitive field types handled by the shipped drivers.
module Field : sig ... endFacilities for extending and using primitive field types.
type _ t = private | Unit : unit t| Field : 'a field -> 'a t| Option : 'a t -> 'a option t| Tup2 : 'a t * 'b t -> ('a * 'b) t| Tup3 : 'a t * 'b t * 'c t -> ('a * 'b * 'c) t| Tup4 : 'a t * 'b t * 'c t * 'd t -> ('a * 'b * 'c * 'd) t| Custom : {rep : 'b t;encode : 'a -> ('b, string) Stdlib.result;decode : 'b -> ('a, string) Stdlib.result;} -> 'a tType descriptor for row types.
Note. The concrete representation of this type should be considered private, including pattern-matching usage; use the below functions for compatibility with future versions.
val length : 'a t -> intlength t is the number of fields used to represent t.
val pp : Stdlib.Format.formatter -> 'a t -> unitpp ppf t prints a human presentation of t on ppf.
val pp_ex : Stdlib.Format.formatter -> ex -> unitpp_ex ppf t prints a human presentation of t on ppf.
val show : 'a t -> stringshow t is a human presentation of t.
val unit : unit tA holding no fields. This is used to pass no parameters and as the result for queries which does not return any rows. It can also be nested in tuples, in which case it will not contribute to the total number of fields.
val custom :
encode:('a -> ('b, string) Stdlib.result) ->
decode:('b -> ('a, string) Stdlib.result) ->
'b t ->
'a tcustom ~encode ~decode rep creates a custom type represented by rep, where encode is used to encode parameters into rep and decode is used to decode result rows from rep.
Note. This should be considered experimental and may be revised or removed in a future version.
field ft is a row of a single field of type ft. This function can be used when adding new field types; use the below functions otherwise.
val bool : bool tA boolean.
val int : int tAn integer.
val int32 : int32 tA 32 bit integer.
val int64 : int64 tA 64 bit integer.
val float : float tA float.
val string : string tAn UTF-8 string. The database should accept UTF-8 if non-ASCII characters are present.
val octets : string tA binary string.
val pdate : Ptime.t tA date. This corresponds to the SQL date type.
val ptime : Ptime.t tAn absolute time with driver-dependent precision. This corresponds to an SQL timestamp type with UTC time zone.
val ptime_span : Ptime.span tA period of time. If the database lacks a dedicated representation, the integer number of seconds is used.