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160 lines
3.9 KiB
ReStructuredText
160 lines
3.9 KiB
ReStructuredText
.. meta::
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:description: Manage computed fields with the Hasura metadata API
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:keywords: hasura, docs, metadata API, API reference, computed field
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.. _metadata_api_computed_field:
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Metadata API Reference: Computed Fields
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=======================================
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.. contents:: Table of contents
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:backlinks: none
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:depth: 1
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:local:
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Introduction
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------------
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**computed field** is an extra field added to a table, its value is
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computed via an SQL function which has the table row type as an input argument.
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Currenty, the Hasura GraphQL engine supports functions returning
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`base types <https://www.postgresql.org/docs/current/extend-type-system.html#id-1.8.3.5.9>`__ or
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`table row types <https://www.postgresql.org/docs/current/rowtypes.html#ROWTYPES-DECLARING>`__
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as computed fields.
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.. admonition:: Supported from
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The metadata API is supported for versions ``v2.0.0`` and above and replaces the older
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:ref:`schema/metadata API <schema_metadata_apis>`.
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.. _pg_add_computed_field:
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pg_add_computed_field
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---------------------
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``pg_add_computed_field`` is used to define a computed field in a table.
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There cannot be an existing column or relationship or computed field with
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the same name.
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Create a ``computed field`` called ``full_name`` on an ``author`` *table*, using
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an SQL function called ``author_full_name``:
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.. code-block:: http
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POST /v1/metadata HTTP/1.1
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Content-Type: application/json
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X-Hasura-Role: admin
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{
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"type":"pg_add_computed_field",
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"args":{
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"table":{
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"name":"author",
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"schema":"public"
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},
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"source": "default",
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"name":"full_name",
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"definition":{
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"function":{
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"name":"author_full_name",
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"schema":"public"
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},
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"table_argument":"author_row"
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}
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}
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}
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.. _pg_add_computed_field_syntax:
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Args syntax
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^^^^^^^^^^^
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.. list-table::
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:header-rows: 1
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* - Key
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- Required
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- Schema
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- Description
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* - table
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- true
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- :ref:`TableName <TableName>`
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- Name of the table
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* - name
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- true
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- :ref:`ComputedFieldName <ComputedFieldName>`
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- Name of the new computed field
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* - definition
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- true
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- :ref:`ComputedFieldDefinition`
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- The computed field definition
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* - comment
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- false
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- text
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- comment
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* - source
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- false
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- :ref:`SourceName <SourceName>`
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- Name of the source database of the table (default: ``default``)
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.. _pg_drop_computed_field:
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pg_drop_computed_field
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----------------------
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``pg_drop_computed_field`` is used to drop a computed field of a table. If
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there are other objects dependent on this computed field, like permissions, the request will fail and report the
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dependencies unless ``cascade`` is set to ``true``. If ``cascade`` is set to ``true``, the dependent objects
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are also dropped.
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Drop a computed field ``full_name`` from a table ``author``:
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.. code-block:: http
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POST /v1/metadata HTTP/1.1
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Content-Type: application/json
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X-Hasura-Role: admin
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{
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"type":"pg_drop_computed_field",
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"args":{
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"table":{
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"name":"author",
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"schema":"public"
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},
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"source": "default",
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"name":"full_name",
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"cascade": false
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}
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}
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.. _pg_drop_computed_field_syntax:
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Args syntax
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^^^^^^^^^^^
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.. list-table::
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:header-rows: 1
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* - Key
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- Required
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- Schema
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- Description
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* - table
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- true
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- :ref:`TableName <TableName>`
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- Name of the table
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* - name
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- true
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- :ref:`ComputedFieldName <ComputedFieldName>`
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- Name of the computed field
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* - cascade
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- false
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- Boolean
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- When set to ``true``, all the dependent items (if any) on this computed fields are also dropped
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* - source
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- false
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- :ref:`SourceName <SourceName>`
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- Name of the source database of the table (default: ``default``)
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