2019-03-28 13:51:58 +03:00
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.. _hasura_metadata_schema:
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2019-01-04 20:25:48 +03:00
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Hasura GraphQL engine metadata schema
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=====================================
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.. contents:: Table of contents
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:backlinks: none
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:depth: 2
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:local:
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2019-09-11 10:17:14 +03:00
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The Hasura GraphQL engine uses a set of internal tables to manage the state of the database and the
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2019-01-04 20:25:48 +03:00
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GraphQL schema. It uses the data in these tables to generate the GraphQL API which then can be accessed
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from different clients.
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2019-09-11 10:17:14 +03:00
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The Hasura GraphQL engine when initialized, creates a schema called ``hdb_catalog`` in the Postgres database and
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2019-01-04 20:25:48 +03:00
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initializes a few tables under it as described below.
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**hdb_catalog** schema
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----------------------
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2019-09-11 10:17:14 +03:00
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This schema is created by the Hasura GraphQL engine to manage its internal state. Whenever a
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table/permission/relationship is created/updated using the Hasura console or the metadata API, the Hasura GraphQL engine
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2019-01-04 20:25:48 +03:00
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captures that information and stores it in the corresponding tables.
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2019-09-11 10:17:14 +03:00
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The following tables are used by the Hasura GraphQL engine:
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2019-01-04 20:25:48 +03:00
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**hdb_table** table
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^^^^^^^^^^^^^^^^^^^
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This table stores information about all the tables/views which are created/tracked using the Hasura console or
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the metadata API.
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Schema
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""""""
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2019-03-13 13:03:45 +03:00
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.. thumbnail:: ../../../img/graphql/manual/engine-internals/hdb_table.jpg
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:width: 30%
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:alt: hdb_table schema
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Column Definitions
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""""""""""""""""""
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+---------------------+------------------------------------------------------------------------------------------+
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| column | description |
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+=====================+==========================================================================================+
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| table_schema | Captures information about the schema under which a table/view is tracked |
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+---------------------+------------------------------------------------------------------------------------------+
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| table_name | Captures name of the tracked table/view. |
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+---------------------+------------------------------------------------------------------------------------------+
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| is_system_defined | If it is true, then the table/view is created by GraphQL engine for internal purpose. |
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| | If it is false, then the table/view is created by the end user. |
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+---------------------+------------------------------------------------------------------------------------------+
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**hdb_relationship** table
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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This table stores information about the relationships created for tables/views using the Hasura console or
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the metadata API.
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Schema
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""""""
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2019-03-13 13:03:45 +03:00
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.. thumbnail:: ../../../img/graphql/manual/engine-internals/hdb_relationship.jpg
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:width: 30%
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:alt: hdb_relationship schema
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Column Definitions
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""""""""""""""""""
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+---------------------+------------------------------------------------------------------------------------------+
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| column | description |
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+=====================+==========================================================================================+
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| table_schema | Captures information about the schema under which a relationship is created. |
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+---------------------+------------------------------------------------------------------------------------------+
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| table_name | Captures name of the table/view under which a relationship is created. |
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+---------------------+------------------------------------------------------------------------------------------+
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| rel_na me | Captures name of the relationship. |
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+---------------------+------------------------------------------------------------------------------------------+
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| rel_type | Captures the permission type (insert/select/update/delete). |
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+---------------------+------------------------------------------------------------------------------------------+
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| perm_def | Captures information about how the relationship is defined. |
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| | |
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| | For example: |
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| | .. code-block:: json |
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| | |
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| | { |
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| | "foreign_key_constraint_on": "user_id" |
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| | } |
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+---------------------+------------------------------------------------------------------------------------------+
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| comment | Captures the comment for the relationship. |
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+---------------------+------------------------------------------------------------------------------------------+
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| is_system_defined | If it is true, then the relationship is created by GraphQL engine for internal purpose. |
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| | If it is false, then the relationship is created by the end user. |
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+---------------------+------------------------------------------------------------------------------------------+
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**hdb_permission** table
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^^^^^^^^^^^^^^^^^^^^^^^^
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This table stores information about the access control rules on tables/views set up using the Hasura console or
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the metadata API.
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Schema
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""""""
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2019-03-13 13:03:45 +03:00
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.. thumbnail:: ../../../img/graphql/manual/engine-internals/hdb_permission.jpg
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:width: 30%
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2019-01-04 20:25:48 +03:00
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:alt: hdb_permission schema
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Column Definitions
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""""""""""""""""""
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+---------------------+------------------------------------------------------------------------------------------+
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| column | description |
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+=====================+==========================================================================================+
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| table_schema | Captures information about the schema under which a permission is created. |
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+---------------------+------------------------------------------------------------------------------------------+
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| table_name | Captures name of the table/view under which a permission is created. |
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+---------------------+------------------------------------------------------------------------------------------+
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| role_name | Captures name of the role for which this permission will be applicable. |
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+---------------------+------------------------------------------------------------------------------------------+
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| perm_type | Captures the permission type (insert/select/update/delete). |
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+---------------------+------------------------------------------------------------------------------------------+
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| perm_def | Captures information about how the permission is defined. |
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| | |
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| | Whenever a query is made with the above role for the above table GraphQL engine |
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| | will first validate the requested columns with the columns which the user has access to |
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| | using the ``columns`` key. |
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| | Once the query is validated the appropriate results are returned after applying the |
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| | filter defined in the ``filter`` key. |
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| | For example: |
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| | .. code-block:: json |
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| | { |
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| | "columns": ["id", "name"], |
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| | "filter": { |
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| | "id": { |
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| | "_eq": "X-HASURA-USER-ID" |
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| | } |
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| | } |
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| | } |
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+---------------------+------------------------------------------------------------------------------------------+
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| comment | Captures the comment for the permission. |
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+---------------------+------------------------------------------------------------------------------------------+
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| is_system_defined | If it is true, then the permission is created by GraphQL engine for internal purpose. If |
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| | it is false, then the permission is created by the end user. |
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+---------------------+------------------------------------------------------------------------------------------+
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