457 lines
11 KiB
ReStructuredText
457 lines
11 KiB
ReStructuredText
.. _s_procs:
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Stored Procedures
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=================
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*"A single resource can be the equivalent of a database stored procedure, with the power to abstract state changes over any number of storage items"* -- `Roy T. Fielding <https://roy.gbiv.com/untangled/2008/rest-apis-must-be-hypertext-driven#comment-743>`_
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Every stored procedure in the :ref:`exposed schema <schemas>` and accessible by the :ref:`active database role <roles>` is executable under the :code:`/rpc` prefix. Procedures can perform any operations allowed by PostgreSQL (read data, modify data, and even DDL operations).
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If they return table types, Stored Procedures can:
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- Use all the same :ref:`read filters as Tables and Views <read>` (horizontal/vertical filtering, counts, limits, etc.).
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- Use :ref:`Resource Embedding <s_proc_embed>`, if the returned table type has relationships to other tables.
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.. note::
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Why the ``/rpc`` prefix? PostgreSQL allows a table or view to have the same name as a function. The prefix allows us to avoid routes collisions.
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Calling with POST
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-----------------
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To supply arguments in an API call, include a JSON object in the request payload. Each key/value of the object will become an argument.
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For instance, assume we have created this function in the database.
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.. code-block:: plpgsql
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CREATE FUNCTION add_them(a integer, b integer)
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RETURNS integer AS $$
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SELECT a + b;
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$$ LANGUAGE SQL IMMUTABLE;
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.. important::
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Whenever you create or change a function you must refresh PostgREST's schema cache. See the section :ref:`schema_reloading`.
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The client can call it by posting an object like
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.. tabs::
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.. code-tab:: http
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POST /rpc/add_them HTTP/1.1
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{ "a": 1, "b": 2 }
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/add_them" \
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-X POST -H "Content-Type: application/json" \
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-d '{ "a": 1, "b": 2 }'
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.. code-block:: json
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3
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.. note::
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PostgreSQL converts identifier names to lowercase unless you quote them like:
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.. code-block:: postgres
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CREATE FUNCTION "someFunc"("someParam" text) ...
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Calling with GET
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----------------
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If the function doesn't modify the database, it will also run under the GET method(see :ref:`access_mode`).
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.. tabs::
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.. code-tab:: http
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GET /rpc/add_them?a=1&b=2 HTTP/1.1
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/add_them?a=1&b=2"
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The function parameter names match the JSON object keys in the POST case, for the GET case they match the query parameters ``?a=1&b=2``.
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.. _s_proc_single_json:
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Functions with a single JSON parameter
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--------------------------------------
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You can also call a function that takes a single parameter of type JSON by sending the header :code:`Prefer: params=single-object` with your request. That way the JSON request body will be used as the single argument.
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.. code-block:: plpgsql
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CREATE FUNCTION mult_them(param json) RETURNS int AS $$
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SELECT (param->>'x')::int * (param->>'y')::int
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$$ LANGUAGE SQL;
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.. tabs::
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.. code-tab:: http
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POST /rpc/mult_them HTTP/1.1
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Prefer: params=single-object
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{ "x": 4, "y": 2 }
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/mult_them" \
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-X POST -H "Content-Type: application/json" \
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-H "Prefer: params=single-object" \
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-d '{ "x": 4, "y": 2 }'
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.. code-block:: json
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8
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.. _s_proc_single_unnamed:
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Functions with a single unnamed parameter
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-----------------------------------------
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You can make a POST request to a function with a single unnamed parameter to send raw ``json/jsonb``, ``bytea``, ``text`` or ``xml`` data.
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To send raw JSON, the function must have a single unnamed ``json`` or ``jsonb`` parameter and the header ``Content-Type: application/json`` must be included in the request.
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.. code-block:: plpgsql
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CREATE FUNCTION mult_them(json) RETURNS int AS $$
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SELECT ($1->>'x')::int * ($1->>'y')::int
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$$ LANGUAGE SQL;
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.. tabs::
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.. code-tab:: http
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POST /rpc/mult_them HTTP/1.1
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Content-Type: application/json
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{ "x": 4, "y": 2 }
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/mult_them" \
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-X POST -H "Content-Type: application/json" \
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-d '{ "x": 4, "y": 2 }'
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.. code-block:: json
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8
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.. note::
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If an overloaded function has a single ``json`` or ``jsonb`` unnamed parameter, PostgREST will call this function as a fallback provided that no other overloaded function is found with the parameters sent in the POST request.
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To send raw XML, the parameter type must be ``xml`` and the header ``Content-Type: text/xml`` must be included in the request.
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To send raw binary, the parameter type must be ``bytea`` and the header ``Content-Type: application/octet-stream`` must be included in the request.
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.. code-block:: plpgsql
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CREATE TABLE files(blob bytea);
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CREATE FUNCTION upload_binary(bytea) RETURNS void AS $$
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INSERT INTO files(blob) VALUES ($1);
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$$ LANGUAGE SQL;
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.. tabs::
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.. code-tab:: http
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POST /rpc/upload_binary HTTP/1.1
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Content-Type: application/octet-stream
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file_name.ext
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/upload_binary" \
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-X POST -H "Content-Type: application/octet-stream" \
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--data-binary "@file_name.ext"
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.. code-block:: http
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HTTP/1.1 200 OK
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[ ... ]
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To send raw text, the parameter type must be ``text`` and the header ``Content-Type: text/plain`` must be included in the request.
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.. _s_procs_array:
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Functions with array parameters
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-------------------------------
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You can call a function that takes an array parameter:
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.. code-block:: postgres
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create function plus_one(arr int[]) returns int[] as $$
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SELECT array_agg(n + 1) FROM unnest($1) AS n;
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$$ language sql;
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.. tabs::
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.. code-tab:: http
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POST /rpc/plus_one HTTP/1.1
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Content-Type: application/json
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{"arr": [1,2,3,4]}
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/plus_one" \
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-X POST -H "Content-Type: application/json" \
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-d '{"arr": [1,2,3,4]}'
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.. code-block:: json
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[2,3,4,5]
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For calling the function with GET, you can pass the array as an `array literal <https://www.postgresql.org/docs/current/arrays.html#ARRAYS-INPUT>`_,
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as in ``{1,2,3,4}``. Note that the curly brackets have to be urlencoded(``{`` is ``%7B`` and ``}`` is ``%7D``).
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.. tabs::
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.. code-tab:: http
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GET /rpc/plus_one?arr=%7B1,2,3,4%7D' HTTP/1.1
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/plus_one?arr=%7B1,2,3,4%7D'"
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.. note::
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For versions prior to PostgreSQL 10, to pass a PostgreSQL native array on a POST payload, you need to quote it and use an array literal:
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.. tabs::
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.. code-tab:: http
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POST /rpc/plus_one HTTP/1.1
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{ "arr": "{1,2,3,4}" }
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/plus_one" \
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-X POST -H "Content-Type: application/json" \
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-d '{ "arr": "{1,2,3,4}" }'
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In these versions we recommend using function parameters of type JSON to accept arrays from the client.
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.. _s_procs_variadic:
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Variadic functions
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------------------
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You can call a variadic function by passing a JSON array in a POST request:
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.. code-block:: postgres
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create function plus_one(variadic v int[]) returns int[] as $$
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SELECT array_agg(n + 1) FROM unnest($1) AS n;
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$$ language sql;
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.. tabs::
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.. code-tab:: http
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POST /rpc/plus_one HTTP/1.1
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Content-Type: application/json
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{"v": [1,2,3,4]}
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/plus_one" \
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-X POST -H "Content-Type: application/json" \
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-d '{"v": [1,2,3,4]}'
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.. code-block:: json
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[2,3,4,5]
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In a GET request, you can repeat the same parameter name:
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.. tabs::
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.. code-tab:: http
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GET /rpc/plus_one?v=1&v=2&v=3&v=4 HTTP/1.1
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/plus_one?v=1&v=2&v=3&v=4"
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Repeating also works in POST requests with ``Content-Type: application/x-www-form-urlencoded``:
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.. tabs::
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.. code-tab:: http
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POST /rpc/plus_one HTTP/1.1
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Content-Type: application/x-www-form-urlencoded
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v=1&v=2&v=3&v=4
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/plus_one" \
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-X POST -H "Content-Type: application/x-www-form-urlencoded" \
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-d 'v=1&v=2&v=3&v=4'
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Table-Valued functions
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----------------------
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A function that returns a table type can be filtered using the same filters as :ref:`tables and views <tables_views>`. They can also use :ref:`Resource Embedding <s_proc_embed>`.
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.. code-block:: postgres
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CREATE FUNCTION best_films_2017() RETURNS SETOF films ..
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.. tabs::
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.. code-tab:: http
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GET /rpc/best_films_2017?select=title,director:directors(*) HTTP/1.1
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/best_films_2017?select=title,director:directors(*)"
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.. tabs::
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.. code-tab:: http
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GET /rpc/best_films_2017?rating=gt.8&order=title.desc HTTP/1.1
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/best_films_2017?rating=gt.8&order=title.desc"
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.. _scalar_functions:
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Scalar functions
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----------------
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PostgREST will detect if the function is scalar or table-valued and will shape the response format accordingly:
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.. tabs::
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.. code-tab:: http
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GET /rpc/add_them?a=1&b=2 HTTP/1.1
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/add_them?a=1&b=2"
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.. code-block:: json
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3
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.. tabs::
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.. code-tab:: http
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GET /rpc/best_films_2017 HTTP/1.1
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/best_films_2017"
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.. code-block:: json
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[
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{ "title": "Okja", "rating": 7.4},
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{ "title": "Call me by your name", "rating": 8},
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{ "title": "Blade Runner 2049", "rating": 8.1}
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]
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To manually choose a return format such as binary, plain text or XML, see the section :ref:`scalar_return_formats`.
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Overloaded functions
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--------------------
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You can call overloaded functions with different number of arguments.
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.. code-block:: postgres
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CREATE FUNCTION rental_duration(customer_id integer) ..
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CREATE FUNCTION rental_duration(customer_id integer, from_date date) ..
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.. tabs::
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.. code-tab:: http
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GET /rpc/rental_duration?customer_id=232 HTTP/1.1
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/rental_duration?customer_id=232"
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.. tabs::
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.. code-tab:: http
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GET /rpc/rental_duration?customer_id=232&from_date=2018-07-01 HTTP/1.1
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/rental_duration?customer_id=232&from_date=2018-07-01"
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.. important::
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Overloaded functions with the same argument names but different types are not supported.
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.. _bulk_call:
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Bulk Call
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---------
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It's possible to call a function in a bulk way, analogously to :ref:`bulk_insert`. To do this, you need to add the
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``Prefer: params=multiple-objects`` header to your request.
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.. tabs::
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.. code-tab:: http
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POST /rpc/add_them HTTP/1.1
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Content-Type: text/csv
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Prefer: params=multiple-objects
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a,b
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1,2
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3,4
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.. code-tab:: bash Curl
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curl "http://localhost:3000/rpc/add_them" \
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-X POST -H "Content-Type: text/csv" \
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-H "Prefer: params=multiple-objects" \
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--data-binary @- << EOF
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a,b
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1,2
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3,4
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EOF
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.. code-block:: json
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[ 3, 7 ]
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If you have large payloads to process, it's preferable you instead use a function with an :ref:`array parameter <s_procs_array>` or JSON parameter, as this will be more efficient.
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It's also possible to :ref:`Specify Columns <specify_columns>` on functions calls.
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