.. _meta_scheme:


Custom Feature Vector Database Structure
=================================================

The database structure is set via the ``tnt-schema.lua`` file.

The structure is created as a set of spaces and fields. Each field is described with the following parameters:

* ``id``: field id;
* ``name``: field name, must be the same as the name of a relevant object parameter;
* ``field_type``: data type (``unsigned|string|set[string]|set[unsigned]``);
* ``default``: field default value. If a default value exceeds ``1e14 – 1``, use a string data type to specify it, for example, ``"123123.."`` instead of ``123123..``.

The following service fields for objects (faces/bodies) in the database are required for correct operation of ``sf-api``.

.. code::

    meta_scheme  = {
      {
          id = 1,
          name = 'feat',
          field_type = 'string',
          default = ""
      },
      {
          id = 2,
          name = 'normalized_id',
          field_type = 'string',
          default = ""
      },
      ...
    }

If you need to use metadata, the meta fields must be defined in the ``tntapi`` configuration file. So the data schema should be as follows:

.. code::



  cfg_spaces = {
    default = {
      meta_scheme = {
        {
          id = 1,
          name = 'feat',
          field_type = 'string',
          default = ""
        },
       {
          id = 2,
          name = 'normalized_id',
          field_type = 'string',
          default = ""
        },
        {
          id = 3,
          name = 'timestamp',
          field_type = 'unsigned',
          default = 0
        },
        {
          id = 4,
          name = 'photo_hash',
          field_type = 'string',
          default = ""
        },
        {
          id = 5,
          name = 'cam_id',
          field_type = 'string',
          default = ""
        },
        {
          id = 6,
          name = 'person_id',
          field_type = 'unsigned',
          default = 0
        },
        {
          id = 7,
          name = 'tags',
          field_type = 'set[string]',
          default = {}
        }
      },
      meta_indexes = {'cam_id', 'person_id'}
    },
    altscheme = {
      meta_scheme = {
        {
          id = 1,
          name = 'feat',
          field_type = 'string',
          default = ""
        },
        {
          id = 2,
          name = 'normalized_id',
          field_type = 'string',
          default = ""
        },
        {
          id = 3,
          name = 'name',
          field_type = 'string',
          default = ""
        }
      },
      meta_indexes = {}
    }
  }