[test] Drop no more used "maxeid" based deletion in BaseQuerierTC and derived tests
This is probably only necessary for QuerierTC itself, move it there and drop
incantation from other derived classes to deactivate this feature.
.. -*- coding: utf-8 -*-
.. _dataimport:
Dataimport
==========
*CubicWeb* is designed to easily manipulate large amounts of data, and provides
utilities to make imports simple.
The main entry point is :mod:`cubicweb.dataimport.importer` which defines an
:class:`ExtEntitiesImporter` class responsible for importing data from an external source in the
form :class:`ExtEntity` objects. An :class:`ExtEntity` is a transitional representation of an
entity to be imported in the CubicWeb instance; building this representation is usually
domain-specific -- e.g. dependent of the kind of data source (RDF, CSV, etc.) -- and is thus the
responsibility of the end-user.
Along with the importer, a *store* must be selected, which is responsible for insertion of data into
the database. There exists different kind of stores_, allowing to insert data within different
levels of the *CubicWeb* API and with different speed/security tradeoffs. Those keeping all the
*CubicWeb* hooks and security will be slower but the possible errors in insertion (bad data types,
integrity error, ...) will be handled.
Example
-------
Consider the following schema snippet.
.. code-block:: python
class Person(EntityType):
name = String(required=True)
class knows(RelationDefinition):
subject = 'Person'
object = 'Person'
along with some data in a ``people.csv`` file::
# uri,name,knows
http://www.example.org/alice,Alice,
http://www.example.org/bob,Bob,http://www.example.org/alice
The following code (using a shell context) defines a function `extentities_from_csv` to read
`Person` external entities coming from a CSV file and calls the :class:`ExtEntitiesImporter` to
insert corresponding entities and relations into the CubicWeb instance.
.. code-block:: python
from cubicweb.dataimport import ucsvreader, RQLObjectStore
from cubicweb.dataimport.importer import ExtEntity, ExtEntitiesImporter
def extentities_from_csv(fpath):
"""Yield Person ExtEntities read from `fpath` CSV file."""
with open(fpath) as f:
for uri, name, knows in ucsvreader(f, skipfirst=True, skip_empty=False):
yield ExtEntity('Person', uri,
{'name': set([name]), 'knows': set([knows])})
extenties = extentities_from_csv('people.csv')
store = RQLObjectStore(cnx)
importer = ExtEntitiesImporter(schema, store)
importer.import_entities(extenties)
commit()
rset = cnx.execute('String N WHERE X name N, X knows Y, Y name "Alice"')
assert rset[0][0] == u'Bob', rset
Importer API
------------
.. automodule:: cubicweb.dataimport.importer
Stores
~~~~~~
.. automodule:: cubicweb.dataimport.stores
SQLGenObjectStore
-----------------
This store relies on *COPY FROM*/execute many sql commands to directly push data using SQL commands
rather than using the whole *CubicWeb* API. For now, **it only works with PostgresSQL** as it requires
the *COPY FROM* command.