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|
.. -*- rst -*-
.. groonga-command
.. database: commands_column_list
``column_list``
===============
Summary
-------
``column_list`` command lists columns in a table.
Syntax
------
This command takes only one required parameter::
column_list table
Usage
-----
Here is a simple example of ``column_list`` command.
.. groonga-command
.. include:: ../../example/reference/commands/column_list/column_list.log
.. table_create Users TABLE_PAT_KEY ShortText
.. column_create Users age COLUMN_SCALAR UInt8
.. column_create Users tags COLUMN_VECTOR ShortText
.. column_list Users
Parameters
----------
This section describes parameters of ``column_list``.
Required parameters
^^^^^^^^^^^^^^^^^^^
All parameters are required.
``table``
"""""""""
Specifies the name of table to be listed columns.
Return value
------------
``column_list`` returns the list of column information in the table::
[
HEADER,
[
COLUMN_LIST_HEADER,
COLUMN_INFORMATION1,
COLUMN_INFORMATION2,
...
]
]
``HEADER``
^^^^^^^^^^
See :doc:`/reference/command/output_format` about ``HEADER``.
``COLUMN_LIST_HEADER``
^^^^^^^^^^^^^^^^^^^^^^
``COLUMN_LIST_HEADER`` describes about content of each
:ref:`column-list-column-information`.
``COLUMN_LIST_HEADER`` uses the following format:
.. code-block:: json
[
["id", "UInt32"],
["name", "ShortText"],
["path", "ShortText"],
["type", "ShortText"],
["flags", "ShortText"],
["domain", "ShortText"],
["range", "ShortText"],
["source", "ShortText"]
["generator", "ShortText"]
]
It means the following:
* The first content in :ref:`column-list-column-information` is
``id`` value and the value type is ``UInt32``.
* The second content in :ref:`column-list-column-information` is
``name`` value and the value type is ``ShortText``.
* The third content :ref:`column-list-column-information` is ....
This field provides meta-data of column information. So this field
will be useful for programs rather than humans.
.. _column-list-column-information:
``COLUMN_INFORMATION``
^^^^^^^^^^^^^^^^^^^^^^
Each ``COLUMN_INFORMATION`` uses the following format::
[
ID,
NAME,
PATH,
TYPE,
FLAGS,
DOMAIN,
RANGE,
SOURCES,
GENERATOR
]
``ID``
""""""
The column ID in the Groonga database. Normally, you don't care about
it.
``NAME``
""""""""
The column name.
``PATH``
""""""""
The path for storing column data.
``TYPE``
""""""""
The type of the column. It is one of the followings:
.. list-table::
:header-rows: 1
* - Value
- Description
* - ``fix``
- The column is a fixed size column. Scalar column that its
type is fixed size type is fixed size column.
* - ``var``
- The column is a variable size column. Vector column or
scalar column that its type is variable size type are
variable size column.
* - ``index``
- The column is an index column.
``FLAGS``
"""""""""
The flags of the column. Each flag is separated by ``|`` like
``COLUMN_VECTOR|WITH_WEIGHT``. ``FLAGS`` must include one of
``COLUMN_SCALAR``, ``COLUMN_VECTOR`` or ``COLUMN_INDEX``. Other
flags are optional.
Here is the available flags:
.. list-table::
:header-rows: 1
* - Flag
- Description
* - ``COLUMN_SCALAR``
- The column is a scalar column.
* - ``COLUMN_VECTOR``
- The column is a vector column.
* - ``COLUMN_INDEX``
- The column is an index column.
* - ``WITH_WEIGHT``
- The column can have weight. ``COLUMN_VECTOR`` and ``COLUMN_INDEX``
may have it. ``COLUMN_SCALAR`` doesn't have it.
* - ``WITH_SECTION``
- The column can have section information. ``COLUMN_INDEX``
may have it. ``COLUMN_SCALAR`` and ``COLUMN_VECTOR`` don't
have it.
Multiple column index has it.
* - ``WITH_POSITION``
- The column can have position information. ``COLUMN_INDEX``
may have it. ``COLUMN_SCALAR`` and ``COLUMN_VECTOR`` don't
have it.
Full text search index must has it.
* - ``PERSISTENT``
- The column is a persistent column. It means that the column
isn't a :doc:`/reference/columns/pseudo`.
``DOMAIN``
""""""""""
The name of table that has the column.
``RANGE``
"""""""""
The value type name of the column. It is a type name or a table name.
``SOURCES``
"""""""""""
An array of the source column names of the index column or the
generated column.
If the index column is a multiple column index, the array has two or
more source column names.
``GENERATOR``
"""""""""""""
.. versionadded:: 14.1.0
The generator expression in :doc:`../grn_expr/script_syntax`.
This is not an empty string only when the column is a
:ref:`generated-column`. This is an empty string otherwise.
See also
--------
* :doc:`/reference/commands/column_create`
* :doc:`/reference/column`
|
