Metadata-Version: 1.1
Name: metapensiero.sphinx.patchdb
Version: 1.1.2
Summary: Extract scripts from a reST document and apply them in order.
Home-page: https://bitbucket.org/lele/metapensiero.sphinx.patchdb
Author: Lele Gaifax
Author-email: lele@metapensiero.it
License: GPLv3+
Description: =============================
         metapensiero.sphinx.patchdb
        =============================
        
        Collects and applies scripts embedded in a reST document
        ========================================================
        
        :version: 1.1.0
        :author: Lele Gaifax <lele@metapensiero.it>
        :license: GPLv3
        
        Building and maintaining the schema of a database is always a challenge. It may quickly become
        a nightmare when dealing with even moderately complex databases, in a distribuited development
        environment. You have new features going in, and fixes here and there, that keeps accumulating
        in the development `branch`. You also have several already deployed instances of the database
        you wanna upgrade now and then.
        
        In my experience, it's very difficult to impossible to come up with a completely automated
        solution, for several reasons:
        
        * comparison between different releases of a database schema is tricky
        
        * actual contents of the database must be preserved
        
        * some changes require specific recipes to upgrade the data
        
        * any automated solution hide some detail, by definition: I need complete control, to be able
          to create temporary tables and/or procedures for example
        
        I tried, and wrote myself, several different approaches to the problem, and this package is my
        latest and most satisfying effort: it builds on top of `docutils`_ and `Sphinx`_, with the side
        advantage that you get a quite nice and good documentation of the whole architecture: `literate
        database scheming`!
        
        .. _docutils: http://docutils.sourceforge.net/
        .. _sphinx: http://sphinx.pocoo.org/intro.html
        
        How it works
        ------------
        
        The package contains two distinct pieces: a `Sphinx`_ extension and the ``patchdb`` command
        line tool.
        
        The extension implements a new `ReST` directive able to embed a `script` in the document: when
        processed by the ``sphinx-build`` tool, all the scripts will be collected in an external file,
        configurable.
        
        The ``patchdb`` tool takes that script collection and determines which scripts need to be
        applied to some database, and the right order.
        
        It keeps and maintains a single very simple table within the database, where it records the
        last version of each script it successfully execute, so that it won't reexecute the same script
        (actually, a particular `revision` of it) twice.
        
        So, on the development side you simply write (and document!) each piece, and when it comes the
        time of deploying current state you distribute just the script collection (a single file,
        usually in `YAML`_ or `JSON`_ format, or a ``pickle`` archive) to the end points where the
        database instances live, and execute ``patchdb`` against each one.
        
        .. _yaml: http://yaml.org/
        .. _json: http://json.org/
        
        Scripts
        ~~~~~~~
        
        The basic building block is a `script`, an arbitrary sequence of statements written in some
        language (currently, either ``Python``, ``SQL`` or ``Shell``), augmented with some metadata
        such as the `scriptid`, possibly a longer `description`, its `revision` and so on.
        
        As a complete example of the syntax, consider the following::
        
          .. patchdb:script:: My first script
             :description: Full example of a script
             :revision: 2
             :depends: Other script@4
             :preceeds: Yet another
             :language: python
             :conditions: python_2_x
        
             print "Yeah!"
        
        This will introduce a script globally identified by `My first script`, written in ``Python``:
        this is its second release, and its execution must be constrained such that it happens
        **after** the execution of the fourth revision of `Other script` and **before** `Yet another`.
        
        The example shows also an usage of the conditions, allowing more than one variant of a script
        like::
        
          .. patchdb:script:: My first script (py3)
             :description: Full example of a script
             :revision: 2
             :depends: Other script@4
             :preceeds: Yet another
             :language: python
             :conditions: python_3_x
        
             print("Yeah!")
        
        The dependencies may be a comma separated list of script ids, such as::
        
          .. patchdb:script:: Create master table
        
             CREATE TABLE some_table (id INTEGER PRIMARY KEY, tt_id INTEGER)
        
          .. patchdb:script:: Create target table
        
             CREATE TABLE target_table (id INTEGER PRIMARY KEY)
        
          .. patchdb:script:: Add foreign key to some_table
             :depends: Create master table, Create target table
        
             ALTER TABLE some_table
                   ADD CONSTRAINT fk_master_target
                       FOREIGN KEY (tt_id) REFERENCES target_table (id)
        
        Independently from the order these scripts appear in the documentation, the third script will
        execute only after the first two get successfully applied to the database. As you can notice,
        most of the options are optional: by default, ``:language:`` is ``sql``, ``:revision:`` is
        ``1``, the ``:description:`` is taken from the title (that is, the script ID), while
        ``:depends:`` and ``:preceeds:`` are empty.
        
        Just for illustration purposes, the same effect could be achieved with::
        
          .. patchdb:script:: Create master table
             :preceeds: Add foreign key to some_table
        
             CREATE TABLE some_table (id INTEGER PRIMARY KEY, tt_id INTEGER)
        
          .. patchdb:script:: Create target table
        
             CREATE TABLE target_table (id INTEGER PRIMARY KEY)
        
          .. patchdb:script:: Add foreign key to some_table
             :depends: Create target table
        
             ALTER TABLE some_table
                   ADD CONSTRAINT fk_master_target
                       FOREIGN KEY (tt_id) REFERENCES target_table (id)
        
        Patches
        ~~~~~~~
        
        A `patch` is a particular flavour of script, one that specify a `brings` dependency
        list. Imagine that the example above was the first version of the database, and that the
        current version looks like the following::
        
          .. patchdb:script:: Create master table
             :revision: 2
        
             CREATE TABLE some_table (
               id INTEGER PRIMARY KEY,
               description VARCHAR(80),
               tt_id INTEGER
             )
        
        that is, ``some_table`` now contains one more field, ``description``.
        
        We need an upgrade path from the first revision of the table to the second::
        
          .. patchdb:script:: Add a description to the master table
             :depends: Create master table@1
             :brings: Create master table@2
        
             ALTER TABLE some_table ADD COLUMN description VARCHAR(80)
        
        When ``patchdb`` examines the database status, it will execute one *or* the other. If the
        script `Create master table` isn't executed yet (for example when operating on a new database),
        it will take the former script (the one that creates the table from scratch).  Otherwise, if
        the database "contains" revision 1 (and not higher than 1) of the script, it will execute the
        latter, bumping up the revision number.
        
        Usage
        -----
        
        Collecting patches
        ~~~~~~~~~~~~~~~~~~
        
        To use it, first of all you must register the extension within the Sphinx environment, adding
        the full name of the package to the ``extensions`` list in the file ``conf.py``, for example::
        
            # Add any Sphinx extension module names here, as strings.
            extensions = ['metapensiero.sphinx.patchdb']
        
        The other required bit of customization is the location of the `on disk scripts storage`,
        i.e. the path of the file that will contain the information about every found script: this is
        kept separated from the documentation itself because you will probably deploy on production
        servers just to update their database. If the filename ends with ``.json`` it will contain a
        JSON formatted array, if it ends with ``.yaml`` the information will be dumped in YAML,
        otherwise it will be a Python ``pickle``. I usually prefer JSON or YAML, because those formats
        are more VCs friendly and open to human inspection.
        
        The location may be set in the same ``conf.py`` as above, like::
        
            # Location of the external storage
            patchdb_storage = '…/dbname.json'
        
        Otherwise, you can set it using the ``-D`` option of the ``sphinx-build`` command, so that you
        can easily share its definition with other rules in a ``Makefile``. I usually put the following
        snippet at the beginning of the ``Makefile`` created by ``sphinx-quickstart``::
        
            TOPDIR ?= ..
            STORAGE ?= $(TOPDIR)/database.json
        
            SPHINXOPTS = -D patchdb_storage=$(STORAGE)
        
        At this point, executing the usual ``make html`` will update the scripts archive: that file
        contains everything is needed to update the database either local or remote; in other words,
        running Sphinx (or even having it installed) is **not** required to update a database.
        
        Updating the database
        ~~~~~~~~~~~~~~~~~~~~~
        
        The other side of the coin is managed by the ``patchdb`` tool, that digests the scripts archive
        and is able to determine which of the scripts are not already applied and eventually does that,
        in the right order.
        
        When your database does already exist and you are just starting using ``patchdb`` you may need
        to force the initial state with the following command::
        
            patchdb --assume-already-applied --postgres "dbname=test" --patch-storage database.json
        
        that will just update the `patchdb` table registering current revision of all the missing
        scripts, without executing them.
        
        You can inspect what will be done, that is obtain the list of not already applied patches, with
        a command like::
        
            patchdb --dry-run --postgres "dbname=test" -s database.json
        
        The `database.json` archive can be sent to the production machines (in some cases I put it in a
        *production* branch of the repository and use the version control tool to update the remote
        machines, in other I simply used ``scp`` or ``rsync`` based solutions).
        
        Example development Makefile snippet
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        
        The following is a snippet that I usually put in my outer ``Makefile``::
        
            export TOPDIR := $(CURDIR)
            DBHOST := localhost
            DBPORT := 5432
            DBNAME := dbname
            DROPDB := dropdb --host=$(DBHOST) --port=$(DBPORT)
            CREATEDB := createdb --host=$(DBHOST) --port=$(DBPORT) --encoding=UTF8
            STORAGE := $(TOPDIR)/$(DBNAME).json
            DSN := host=$(DBHOST) port=$(DBPORT) dbname=$(DBNAME)
            PUP := $(PATCHDB) --patch-storage=$(STORAGE) \
                              --postgres="$(DSN)" --log-file=$(DBNAME).log
        
            # Build the Sphinx documentation
            doc:
                    $(MAKE) -C doc STORAGE=$(STORAGE) html
        
            $(STORAGE): doc
        
            # Show what is missing
            missing-patches: $(STORAGE)
                    $(PUP) --dry-run
        
            # Upgrade the database to the latest revision
            database: $(STORAGE)
                    $(PUP)
        
            # Remove current database and start from scratch
            scratch-database:
                    -$(DROPDB) $(DBNAME)
                    $(CREATEDB) $(DBNAME)
                    $(MAKE) database
        
        
        Changes
        -------
        
        1.1.2 (2014-06-05)
        ~~~~~~~~~~~~~~~~~~
        
        * New --assume-already-applied option, useful when you start using ``patchdb``
          on an already existing database
        
        
        1.1.1 (2014-06-03)
        ~~~~~~~~~~~~~~~~~~
        
        * Fix packaging, adding a MANIFEST.in
        
        
        1.1.0 (2014-06-03)
        ~~~~~~~~~~~~~~~~~~
        
        * Use setuptools instead of distribute
        
        * Use argparse instead of optparse
        
        * New mimetype property on scripts, to select the right Pygments highlighter
        
        * New MySQL specific context, using cymysql
        
        
        1.0.7 (2013-08-23)
        ~~~~~~~~~~~~~~~~~~
        
        * published on bitbucket
        
        
        1.0.6 (2013-03-12)
        ~~~~~~~~~~~~~~~~~~
        
        * dbloady: ability to load field values from external files
        
        
        1.0.5 (2013-03-11)
        ~~~~~~~~~~~~~~~~~~
        
        * dbloady: fix encoding error when printing messages coming from PostgresQL
        
        * dbloady: emit a progress bar on stderr
        
        
        1.0.4 (2013-02-27)
        ~~~~~~~~~~~~~~~~~~
        
        * dbloady, a new utility script, to load base data from a YAML stream.
        
        
        1.0.3 (2012-11-07)
        ~~~~~~~~~~~~~~~~~~
        
        * Fix ``:patchdb:script`` role
        
        
        1.0.2 (2012-10-19)
        ~~~~~~~~~~~~~~~~~~
        
        * Pickier way to split the multi-statements SQL scripts, now the
          ``;;`` separator must be on a line by its own
        
        * More precise line number tracking when applying multi-statements SQL
          scripts
        
        * Dump and load script dependencies and conditions as lists, to avoid
          pointless repeated splits and joins
        
        
        1.0.1 (2012-10-13)
        ~~~~~~~~~~~~~~~~~~
        
        * Fix error loading JSON storage, simplejson already yields unicode strings
        
        * Possibly use the original title of the script as description, if not
          explicitly set
        
        * More precise error on unknown script reference
        
        * Minor corrections
        
        
        1.0 (2012-10-10)
        ~~~~~~~~~~~~~~~~
        
        * Added JSON support for the on disk `scripts storage`
        
        * Adapted to work with SQLAlchemy 0.7.x
        
        * Updated to work with docutils > 0.8
        
        * Refactored as a `Sphinx domain <http://sphinx.pocoo.org/domains.html>`_
        
          .. attention:: This means that the directive names are now prefixed
                         with ``patchdb:`` (that is, the old ``script``
                         directive is now ``patchdb:script``). You can use the
                         `default-domain`__ directive if that annoys you.
        
          __ http://sphinx.pocoo.org/domains.html#directive-default-domain
        
        * Renamed the status table from ``prst_applied_info`` to simply
          ``patchdb``
        
          .. attention:: This is the main incompatible change with previous
                         version: you should eventually rename the table
                         manually, sorry for the inconvenience.
        
        * Renamed ``prst_patch_storage`` configuration setting to
          ``patchdb_storage``
        
        * Each script ID is now lower case, to avoid ambiguities
        
        
        0.3 (2010-11-14)
        ~~~~~~~~~~~~~~~~
        
        * Updated to work with Sphinx 1.0
        
        * New :script: role for cross-references
        
        * New :file: option on script directive, to keep the actual text in an
          external file
        
        
        0.2 (2010-03-03)
        ~~~~~~~~~~~~~~~~
        
        * Compatibility with SQLAlchemy 0.6
        
        * New patchdb command line tool
        
        
        0.1 (2009-10-28)
        ~~~~~~~~~~~~~~~~
        
        * Replace home brew solution with SQLAlchemy topological sort
        
        * Use YAML for the persistent storage
        
        * Mostly working Sphinx adaptor
        
        * Rudimentary and mostly untested SQLAlchemy backend (basically only
          the direct PostgresQL backend has been battle tested in production...)
        
        * First standalone version
        
        
        0.0
        ~~~
        
        * still a PylGAM side-product
        
        * simply a set of docutils directives
        
        * started with Firebird in mind, but grown up with PostgresQL
        
Platform: UNKNOWN
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3.3
Classifier: Development Status :: 5 - Production/Stable
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)
Classifier: Topic :: Database
