Postgrex v0.15.5 Postgrex.Types View Source
Encodes and decodes between PostgreSQL protocol and Elixir values.
Link to this section Summary
Types
PostgreSQL internal identifier that maps to a type. See http://www.postgresql.org/docs/9.4/static/datatype-oid.html.
State used by the encoder/decoder functions
Term used to describe type information
Functions
Defines a type module with custom extensions and options.
Link to this section Types
Specs
oid() :: pos_integer()
PostgreSQL internal identifier that maps to a type. See http://www.postgresql.org/docs/9.4/static/datatype-oid.html.
Specs
state()
State used by the encoder/decoder functions
Specs
type()
Term used to describe type information
Link to this section Functions
Defines a type module with custom extensions and options.
Postgrex.Types.define/3
must be called on its own file, outside of
any module and function, as it only needs to be defined once during
compilation.
Type modules are given to Postgrex on start_link
via the :types
option and are used to control how Postgrex encodes and decodes data
coming from Postgrex.
For example, to define a new type module with a custom extension
called MyExtension
while also changing Postgrex
's default
behaviour regarding binary decoding, you may create a new file
called "lib/my_app/postgrex_types.ex" with the following:
Postgrex.Types.define(MyApp.PostgrexTypes, [MyExtension], [decode_binary: :reference])
The line above will define a new module, called MyApp.PostgrexTypes
which can be passed as :types
when starting Postgrex. The type module
works by rewriting and inlining the extensions' encode and decode
expressions in an optimal fashion for postgrex to encode parameters and
decode multiple rows at a time.
Extensions
Extensions is a list of Postgrex.Extension
modules or a 2-tuple
containing the module and a keyword list. The keyword, defaulting
to []
, will be passed to the modules init/1
callback.
Extensions at the front of the list will take priority over later
extensions when the matching/1
callback returns have conflicting
matches. If an extension is not provided for a type then Postgrex
will fallback to default encoding/decoding methods where possible.
All extensions that ship as part of Postgrex are included out of the
box.
See Postgrex.Extension
for more information on extensions.
Options
:null
- The atom to use as a stand in for postgres'NULL
in encoding and decoding. The module attribute@null
is registered with the value so that extension can access the value if desired (default:nil
);:decode_binary
- Either:copy
to copy binary values when decoding with default extensions that return binaries or:reference
to use a reference counted binary of the binary received from the socket. Referencing a potentially larger binary can be more efficient if the binary value is going to be garbaged collected soon because a copy is avoided. However the larger binary can not be garbage collected until all references are garbage collected (default::copy
);:json
- The JSON module to encode and decode JSON binaries, callsmodule.encode_to_iodata!/1
to encode andmodule.decode!/1
to decode. Ifnil
then no default JSON handling (default:Application.get_env(:postgrex, :json_library, Jason)
);:bin_opt_info
- Eithertrue
to enable binary optimisation information, orfalse
to disable, for more information seeKernel.SpecialForms.<<>>/1
in Elixir (default:false
);:debug_defaults
- Generate debug information when building default extensions so they point to the proper source. Enabling such option will increase the time to compile the type module (default:false
);