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−.. -*- coding: utf-8 -*-
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−
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−.. _migration:
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−
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−Migration
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−=========
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−
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−One of the main design goals of *CubicWeb* was to support iterative and agile
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−development. For this purpose, multiple actions are provided to facilitate the
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−improvement of an instance, and in particular to handle the changes to be
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−applied to the data model, without loosing existing data.
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−
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−The current version of a cube (and of cubicweb itself) is provided in the file
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−`__pkginfo__.py` as a tuple of 3 integers.
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−
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−Migration scripts management
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−----------------------------
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−
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−Migration scripts has to be located in the directory `migration` of your
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−cube and named accordingly:
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−
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−::
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−
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−  <version n° X.Y.Z>[_<description>]_<mode>.py
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−
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−in which :
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−
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−* X.Y.Z is the model version number to which the script enables to migrate.
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−
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−* *mode* (between the last "_" and the extension ".py") is used for
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−  distributed installation. It indicates to which part
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−  of the application (RQL server, web server) the script applies.
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−  Its value could be :
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−
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−  * `common`, applies to the RQL server as well as the web server and updates
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−    files on the hard drive (configuration files migration for example).
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−
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−  * `web`, applies only to the web server and updates files on the hard drive.
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−
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−  * `repository`, applies only to the RQL server and updates files on the
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−    hard drive.
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−
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−  * `Any`, applies only to the RQL server and updates data in the database
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−    (schema and data migration for example).
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−
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−Again in the directory `migration`, the file `depends.map` allows to indicate
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−that for the migration to a particular model version, you always have to first
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−migrate to a particular *CubicWeb* version. This file can contain comments (lines
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−starting with `#`) and a dependency is listed as follows: ::
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−
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−  <model version n° X.Y.Z> : <cubicweb version n° X.Y.Z>
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−
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−For example: ::
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−
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−  0.12.0: 2.26.0
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−  0.13.0: 2.27.0
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−  # 0.14 works with 2.27 <= cubicweb <= 2.28 at least
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−  0.15.0: 2.28.0
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−
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−Base context
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−------------
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−
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−The following identifiers are pre-defined in migration scripts:
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−
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−* `config`, instance configuration
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−
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−* `interactive_mode`, boolean indicating that the script is executed in
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−  an interactive mode or not
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−
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−* `versions_map`, dictionary of migrated versions  (key are cubes
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−  names, including 'cubicweb', values are (from version, to version)
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−
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−* `confirm(question)`, function asking the user and returning true
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−  if the user answers yes, false otherwise (always returns true in
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−  non-interactive mode)
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−
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−* `_()` is equivalent to `unicode` allowing to flag the strings to
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−  internationalize in the migration scripts.
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−
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−In the `repository` scripts, the following identifiers are also defined:
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−
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−* `commit(ask_confirm=True)`, request confirming and executing a "commit"
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−
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−* `schema`, instance schema (readen from the database)
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−
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−* `fsschema`, installed schema on the file system (e.g. schema of
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−  the updated model and cubicweb)
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−
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−* `repo`, repository object
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−
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−* `session`, repository session object
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−
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−
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−New cube dependencies
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−---------------------
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−
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−If your code depends on some new cubes, you have to add them in a migration
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−script by using:
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−
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−* `add_cube(cube, update_database=True)`, add a cube.
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−* `add_cubes(cubes, update_database=True)`, add a list of cubes.
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−
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−The `update_database` parameter is telling if the database schema
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−should be updated or if only the relevant persistent property should be
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−inserted (for the case where a new cube has been extracted from an
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−existing one, so the new cube schema is actually already in there).
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−
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−If some of the added cubes are already used by an instance, they'll simply be
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−silently skipped.
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−
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−To remove a cube use `drop_cube(cube, removedeps=False)`. 
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−
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−Schema migration
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−----------------
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−The following functions for schema migration are available in `repository`
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−scripts:
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−
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−* `add_attribute(etype, attrname, attrtype=None, commit=True)`, adds a new
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−  attribute to an existing entity type. If the attribute type is not specified,
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−  then it is extracted from the updated schema.
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−
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−* `drop_attribute(etype, attrname, commit=True)`, removes an attribute from an
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−  existing entity type.
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−
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−* `rename_attribute(etype, oldname, newname, commit=True)`, renames an attribute
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−
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−* `add_entity_type(etype, auto=True, commit=True)`, adds a new entity type.
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−  If `auto` is True, all the relations using this entity type and having a known
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−  entity type on the other hand will automatically be added.
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−
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−* `drop_entity_type(etype, commit=True)`, removes an entity type and all the
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−  relations using it.
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−
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−* `rename_entity_type(oldname, newname, commit=True)`, renames an entity type
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−
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−* `add_relation_type(rtype, addrdef=True, commit=True)`, adds a new relation
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−  type. If `addrdef` is True, all the relations definitions of this type will
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−  be added.
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−
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−* `drop_relation_type(rtype, commit=True)`, removes a relation type and all the
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−  definitions of this type.
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−
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−* `rename_relation_type(oldname, newname, commit=True)`, renames a relation type.
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−
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−* `add_relation_definition(subjtype, rtype, objtype, commit=True)`, adds a new
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−  relation definition.
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−
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−* `drop_relation_definition(subjtype, rtype, objtype, commit=True)`, removes
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−  a relation definition.
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−
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−* `sync_schema_props_perms(ertype=None, syncperms=True, syncprops=True, syncrdefs=True, commit=True)`,
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−  synchronizes properties and/or permissions on:
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−  - the whole schema if ertype is None
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−  - an entity or relation type schema if ertype is a string
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−  - a relation definition  if ertype is a 3-uple (subject, relation, object)
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−
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−* `change_relation_props(subjtype, rtype, objtype, commit=True, **kwargs)`, changes
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−  properties of a relation definition by using the named parameters of the properties
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−  to change.
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−
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−* `set_widget(etype, rtype, widget, commit=True)`, changes the widget used for the
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−  relation <rtype> of entity type <etype>.
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−
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−* `set_size_constraint(etype, rtype, size, commit=True)`, changes the size constraints
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−  for the relation <rtype> of entity type <etype>.
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−
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−Data migration
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−--------------
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−The following functions for data migration are available in `repository` scripts:
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−
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−* `rql(rql, kwargs=None, cachekey=None, ask_confirm=True)`, executes an arbitrary RQL
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−  query, either to interrogate or update. A result set object is returned.
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−
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−* `add_entity(etype, *args, **kwargs)`, adds a new entity of the given type.
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−  The attribute and relation values are specified as named positional
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−  arguments.
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−
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−Workflow creation
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−-----------------
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−
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−The following functions for workflow creation are available in `repository`
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−scripts:
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−
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−* `add_workflow(label, workflowof, initial=False, commit=False, **kwargs)`, adds a new workflow
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−  for a given type(s)
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−
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−You can find more details about workflows in the chapter :ref:`Workflow` .
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−
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−Configuration migration
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−-----------------------
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−
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−The following functions for configuration migration are available in all
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−scripts:
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−
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−* `option_renamed(oldname, newname)`, indicates that an option has been renamed
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−
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−* `option_group_change(option, oldgroup, newgroup)`, indicates that an option does not
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−  belong anymore to the same group.
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−
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−* `option_added(oldname, newname)`, indicates that an option has been added.
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−
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−* `option_removed(oldname, newname)`, indicates that an option has been deleted.
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−
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−The `config` variable is an object which can be used to access the
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−configuration values, for reading and updating, with a dictionary-like
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−syntax. 
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−
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−Example 1: migration script changing the variable 'sender-addr' in
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−all-in-one.conf. The script also checks that in that the instance is
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−configured with a known value for that variable, and only updates the
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−value in that case.
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−
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−.. sourcecode:: python
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−
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− wrong_addr = 'cubicweb@loiglab.fr' # known wrong address
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− fixed_addr = 'cubicweb@logilab.fr'
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− configured_addr = config.get('sender-addr')
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− # check that the address has not been hand fixed by a sysadmin
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− if configured_addr == wrong_addr: 
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−     config['sender-addr'] = fixed-addr
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−     config.save()
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−
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−Example 2: checking the value of the database backend driver, which
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−can be useful in case you need to issue backend-dependent raw SQL
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−queries in a migration script.
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−
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−.. sourcecode:: python
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−
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− dbdriver  = config.sources()['system']['db-driver']
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− if dbdriver == "sqlserver2005":
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−     # this is now correctly handled by CW :-)
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−     sql('ALTER TABLE cw_Xxxx ALTER COLUMN cw_name varchar(64) NOT NULL;')
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−     commit()
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− else: # postgresql
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−     sync_schema_props_perms(ertype=('Xxxx', 'name', 'String'),
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−     syncperms=False)
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−
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−
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−Others migration functions
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−--------------------------
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−Those functions are only used for low level operations that could not be
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−accomplished otherwise or to repair damaged databases during interactive
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−session. They are available in `repository` scripts:
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−
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−* `sql(sql, args=None, ask_confirm=True)`, executes an arbitrary SQL query on the system source
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−* `add_entity_type_table(etype, commit=True)`
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−* `add_relation_type_table(rtype, commit=True)`
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−* `uninline_relation(rtype, commit=True)`
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−
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−
+
−[FIXME] Add explanation on how to use cubicweb-ctl shell