.. -*- rst -*-

.. highlightlang:: none

.. groonga-command
.. database: functions_query

``query``
=========

Summary
-------

``query`` provides ``--match_columns`` and ``--query`` parameters of
:doc:`/reference/commands/select` feature as function. You can specify
multiple ``query`` functions in ``--filter`` parameter in
:doc:`/reference/commands/select`.

Because of such flexibility, you can control full text search behavior
by combination of multiple ``query`` functions.

``query`` can be used in only ``--filter`` in
:doc:`/reference/commands/select`.

Syntax
------

``query`` requires two arguments - ``match_columns`` and ``query_string``.

The parameter ``query_expander`` or ``substitution_table`` is optional.

::

  query(match_columns, query_string)
  query(match_columns, query_string, query_expander)
  query(match_columns, query_string, substitution_table)


Usage
-----

Here are a schema definition and sample data to show usage.

Sample schema:

.. groonga-command
.. include:: ../../example/reference/functions/query/usage_setup_schema.log
.. table_create Documents TABLE_NO_KEY
.. column_create Documents content COLUMN_SCALAR Text
.. table_create Terms TABLE_PAT_KEY ShortText --default_tokenizer TokenBigram  --normalizer NormalizerAuto
.. column_create Terms documents_content_index COLUMN_INDEX|WITH_POSITION Documents content
.. table_create Users TABLE_NO_KEY
.. column_create Users name COLUMN_SCALAR ShortText
.. column_create Users memo COLUMN_SCALAR ShortText
.. table_create Lexicon TABLE_HASH_KEY ShortText \
..   --default_tokenizer TokenBigramSplitSymbolAlphaDigit \
..   --normalizer NormalizerAuto
.. column_create Lexicon users_name COLUMN_INDEX|WITH_POSITION Users name
.. column_create Lexicon users_memo COLUMN_INDEX|WITH_POSITION Users memo

Sample data:

.. groonga-command
.. include:: ../../example/reference/functions/query/usage_setup_data.log
.. load --table Users
.. [
.. {"name": "Alice", "memo": "groonga user"},
.. {"name": "Alisa", "memo": "mroonga user"},
.. {"name": "Bob",   "memo": "rroonga user"},
.. {"name": "Tom",   "memo": "nroonga user"},
.. {"name": "Tobby", "memo": "groonga and mroonga user. mroonga is ..."},
.. ]

Here is the simple usage of ``query`` function which execute full text
search by keyword 'alice' without using ``--match_columns`` and
``--query`` arguments in ``--filter``.

.. groonga-command
.. include:: ../../example/reference/functions/query/usage_basic.log
.. select Users --output_columns name,_score --filter 'query("name * 10", "alice")'

When executing above query, the keyword 'alice' is weighted to the value -
'10'.

Here are the contrasting examples with/without ``query``.

.. groonga-command
.. include:: ../../example/reference/functions/query/usage_without_query.log
.. select Users --output_columns name,memo,_score --match_columns "memo * 10" --query "memo:@groonga OR memo:@mroonga OR memo:@user" --sortby -_score

In this case, the keywords 'groonga' and 'mroonga' and 'user' are
given same weight value.
You can't pass different weight value to each keyword in this way.


.. groonga-command
.. include:: ../../example/reference/functions/query/usage_with_query.log
.. select Users --output_columns name,memo,_score --filter 'query("memo * 10", "groonga") || query("memo * 20", "mroonga") || query("memo * 1", "user")' --sortby -_score

On the other hand, by specifying multiple ``query``, the keywords
'groonga' and 'mroonga' and 'user' are given different value of weight.

As a result, you can control full text search result by giving different weight to the
keywords on your purpose.

Parameters
----------

Required parameter
^^^^^^^^^^^^^^^^^^

There are two required parameter, ``match_columns`` and ``query_string``.

``match_columns``
"""""""""""""""""

Specifies the default target column for fulltext search by
``query_string`` parameter value. It is the same role as
:ref:`select-match-columns` parameter in ``select``.

``query_string``
""""""""""""""""

Specifies the search condition in
:doc:`/reference/grn_expr/query_syntax`. It is the same role as
``query`` parameter in ``select``.

See :ref:`select-match-columns` about ``query`` parameter in
``select``.

Optional parameter
^^^^^^^^^^^^^^^^^^

There are some optional parameters.

``query_expander``
""""""""""""""""""

Specifies the plugin name for query expansion.

There is one plugin bundled in official release - :doc:`/reference/query_expanders/tsv`.

See :doc:`/reference/query_expanders/tsv` about details.


``substitution_table``
""""""""""""""""""""""

Specifies the substitution table and substitution column name
by following format such as ``${TABLE}.${COLUMN}`` for query expansion.

See :ref:`select-query-expander` about details.

Return value
------------

``query`` returns whether any record is matched or not. If one or more
records are matched, it returns ``true``. Otherwise, it returns
``false``.

TODO
----

* Support query_flags

See also
--------

* :doc:`/reference/commands/select`
