[server] Make connection pooler configurable and set better default values
Drop the configuration connections-pool-size and add new configurations options:
* connections-pool-min-size. Set to 0 by default so we open connections only
when needed. This avoid opening min-size*processes connections at startup,
which is, it think, a good default.
* connections-pool-max-size. Set to 0 (unlimited) by default, so we move the
bottleneck to postgresql.
* connections-idle-timeout. Set to 10 minutes. I don't have arguments about
this except that this is the default in pgbouncer.
.. _rql_usecases:
RQL usecases
------------
Search bar
~~~~~~~~~~
The search bar is available on a CubicWeb instance to use RQL and it's use and
configuration is described in `:doc:_searchbar`
Use of RQL in Card documents - ReST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
With a CubicWeb instance supporting object types with ReST content (for example
`Card <https://www.cubicweb.org/project/cubicweb-card>`_), one can build content
based on RQL queries as dynamic documents.
For this, use the `rql` and `rql-table` ReST directive, for more information
about custom ReST directives `head over to the sphinx documentation
<https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html>`_
which uses them extensivelly.
rql directive
~~~~~~~~~~~~~
The `rql` directive takes as input an RQL expression and a view to apply to the
result.
For example, create a Card content by opening
http://cubicweb_example.org/add/Card and add the following content, as an
example : a table of blog entries (10 most recent blog entries table with user
and date information) ::
Recent blog entries
-------------------
:rql:`Any B,U,D ORDERBY D DESC LIMIT 10 WHERE B is BlogEntry, B title T, B creation_date D, B created_by U:table`
.. image:: ../../images/example-card-with-rql-directive.png
rql-table directive
~~~~~~~~~~~~~~~~~~~
`rql-table` enables more customization, enabling you to modify the column
(`header`) contents, and the view applied for a specific column (`colvids`).
For example, create a Card content by openning http://cubicweb_example.org/add/Card and add the following content ::
Blog entries with rql-table
-----------------------------
.. rql-table::
:vid: table
:headers: Title with link, who wrote it, at what date
:colvids: 1=sameetypelist
Any B,U,D ORDERBY D DESC LIMIT 10 WHERE B is BlogEntry, B title T, B creation_date D, B created_by U
All fields but the RQL string are optionnal. The ``:headers:`` option can
contain empty column names.
.. image:: ../../images/example-card-with-rql-table-directive.png
Use in python projects and CLI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`cwclientlib <https://pypi.org/project/cwclientlib/>` enables you to use RQL
in your python projects using only web requests. This project also provides a
remote command line interface (CLI) you can use to replace a server side
`cubicweb-ctl shell`.
Use in JavaScript/React components
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`cwclientelements <https://forge.extranet.logilab.fr/open-source/cwclientelements>`
is a library of reusable React components for building web application with
cubicweb and RQL.