Metadata-Version: 1.1
Name: pg_query
Version: 0.12
Summary: Pythonic wrapper around libpg_query and SQL prettifier
Home-page: https://github.com/lelit/pg_query
Author: Lele Gaifax
Author-email: lele@metapensiero.it
License: GPLv3+
Description: .. -*- coding: utf-8 -*-
        .. :Project:   pg_query -- Pythonic wrapper around libpg_query
        .. :Created:   mer 02 ago 2017 14:49:24 CEST
        .. :Author:    Lele Gaifax <lele@metapensiero.it>
        .. :License:   GNU General Public License version 3 or later
        .. :Copyright: © 2017 Lele Gaifax
        ..
        
        ==========
         pg_query
        ==========
        
        Pythonic wrapper around libpg_query and SQL prettifier
        ======================================================
        
         :author: Lele Gaifax
         :contact: lele@metapensiero.it
         :license: GNU General Public License version 3 or later
        
        This is a Python 3 implementation of a wrapper to `libpg_query`__, a C library that repackages
        the PostgreSQL__ languages parser as a standalone static library.
        
        __ https://github.com/lfittl/libpg_query
        __ https://www.postgresql.org/
        
        I needed a better SQL reformatter than the one implemented by `sqlparse`__, and was annoyed by
        a few glitches (subselects__ in particular) that ruins the otherwise excellent job it does,
        considering that it is a generic library that tries to swallow many different SQL dialects.
        
        __ https://pypi.org/project/sqlparse/
        __ https://github.com/andialbrecht/sqlparse/issues/334
        
        When I found `psqlparse`__ I decided to try implementing a PostgreSQL `focused tool`__: at the
        beginning it's been easier than I feared, but I quickly hit some shortcomings in that
        implementation, so I opted for writing my own solution restarting from scratch, with the
        following goals:
        
        __ https://github.com/alculquicondor/psqlparse
        __ https://github.com/alculquicondor/psqlparse/pull/22
        
        - target only Python 3.4+
        
        - target PostgreSQL 10 (in `beta 2`__ as I'm writing this), taking advantage of a
          work-in-progress `branch`__ of the libpg_query library
        
        __ https://www.postgresql.org/about/news/1763/
        __ https://github.com/lfittl/libpg_query/tree/10-latest
        
        - use a more dynamic approach to represent the *parse tree*, with a twofold advantage:
        
          1. it is much less boring to code, because there's no need to write one Python class for each
             PostgreSQL node tag
        
          2. the representation is version agnostic, it can be adapted to newer/older Elephants in a
             snap
        
        - allow exploration of parse tree in both directions, because I realized that some kinds of
          nodes require that knowledge to determine their textual representation
        
        - avoid introducing arbitrary renames of tags and attributes, so what you read in PostgreSQL
          documentation/sources\ [*]_ is available without the hassle of guessing how a symbol has been
          mapped
        
        - use a `zero copy`__ approach, keeping the original parse tree returned from the underlying
          libpg_query functions and have each node just borrow a reference to its own subtree
        
        __ https://en.wikipedia.org/wiki/Zero-copy
        
        .. [*] Currently what you can find in the following headers:
        
               - `nodes.h`__
               - `primnodes.h`__
               - `parsenodes.h`__
               - `lockoptions.h`__
        
        __ https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/include/nodes/nodes.h;hb=HEAD
        __ https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/include/nodes/primnodes.h;hb=HEAD
        __ https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/include/nodes/parsenodes.h;hb=HEAD
        __ https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/include/nodes/lockoptions.h;hb=HEAD
        
        Introduction
        ------------
        
        At the lower level the module exposes two libpg_query functions, ``parse_sql()`` and
        ``parse_plpgsql()``, that take respectively an ``SQL`` statement and a ``PLpgSQL`` statement
        and return a *parse tree* as a hierarchy of Python dictionaries, lists and scalar values. In
        some cases these scalars correspond to some C ``typedef enums``, that are automatically
        extracted from the PostgreSQL headers and are available as ``pg_query.enums``.
        
        At a higher level that tree is represented by three Python classes, a ``Node`` that represents
        a single node, a ``List`` that wraps a sequence of nodes and a ``Scalar`` for plain values such
        a *strings*, *integers*, *booleans* or *none*.
        
        Every node is identified by a *tag*, a string label that characterize its content that is
        exposed as a set of *attributes* as well as with a dictionary-like interface (technically they
        implements both a ``__getattr__`` method and a ``__getitem__`` method). When asked for an
        attribute, the node returns an instance of the base classes, i.e. another ``Node``, or a
        ``List`` or a ``Scalar``, depending on the data type of that item. When the node does not
        contain the requested attribute it returns a singleton ``Missing`` marker instance.
        
        A ``List`` wraps a plain Python ``list`` and may contains a sequence of ``Node`` instances, or
        in some cases other sub-lists, that can be accessed with the usual syntax, or iterated.
        
        Finally, a ``Scalar`` carries a single value of some type, accessible through its ``value``
        attribute.
        
        On top of that, the module implements two serializations, one that transforms a ``Node`` into a
        *raw* textual representation and another that returns a *prettified* representation. The latter
        is exposed by the ``__main__`` entry point of the package, see below for an example.
        
        Installation
        ------------
        
        As usual, the easiest way is with pip::
        
          $ pip install pg_query
        
        Alternatively you can clone the repository::
        
          $ git clone https://github.com/lelit/pg_query.git --recursive
        
        and install from there::
        
          $ pip install ./pg_query
        
        Development
        -----------
        
        There is a set of *makefiles* implementing the most common operations, a ``make help`` will
        show a brief table of contents. A comprehensive test suite, based on pytest__, covers 98% of
        the source lines.
        
        __ https://docs.pytest.org/en/latest/
        
        Examples of usage
        -----------------
        
        * Parse an ``SQL`` statement and get its *AST* root node::
        
           >>> from pg_query import Node, parse_sql
           >>> root = Node(parse_sql('SELECT foo FROM bar'))
           >>> print(root)
           None=[1*{RawStmt}]
        
        * Recursively traverse the parse tree::
        
           >>> for node in root.traverse():
           ...   print(node)
           ...
           None[0]={RawStmt}
           stmt={SelectStmt}
           fromClause[0]={RangeVar}
           inh=<True>
           location=<16>
           relname=<'bar'>
           relpersistence=<'p'>
           op=<0>
           targetList[0]={ResTarget}
           location=<7>
           val={ColumnRef}
           fields[0]={String}
           str=<'foo'>
           location=<7>
        
          As you can see, the ``repr``\ esentation of each value is mnemonic: ``{some_tag}`` means a
          ``Node`` with tag ``some_tag``, ``[X*{some_tag}]`` is a ``List`` containing `X` nodes of that
          particular kind\ [*]_ and ``<value>`` is a ``Scalar``.
        
        * Get a particular node::
        
           >>> from_clause = root[0].stmt.fromClause
           >>> print(from_clause)
           fromClause=[1*{RangeVar}]
        
        * Obtain some information about a node::
        
           >>> range_var = from_clause[0]
           >>> print(range_var.node_tag)
           RangeVar
           >>> print(range_var.attribute_names)
           dict_keys(['relname', 'inh', 'relpersistence', 'location'])
           >>> print(range_var.parent_node)
           stmt={SelectStmt}
        
        * Iterate over nodes::
        
           >>> for a in from_clause:
           ...     print(a)
           ...     for b in a:
           ...         print(b)
           ...
           fromClause[0]={RangeVar}
           inh=<True>
           location=<16>
           relname=<'bar'>
           relpersistence=<'p'>
        
        * Reformat a SQL statement\ [*]_ from the command line::
        
           $ echo "select a,b,c from sometable" | python -m pg_query
           SELECT a
                , b
                , c
           FROM sometable
        
           $ echo 'update "table" set value=123 where value is null' | python -m pg_query
           UPDATE "table"
           SET value = 123
           WHERE value IS NULL
        
        * Programmatically reformat a SQL statement::
        
           >>> from pg_query import prettify
           >>> print(prettify('delete from sometable where value is null'))
           DELETE FROM sometable
           WHERE value IS NULL
        
        Documentation
        -------------
        
        Latest documentation is hosted by `Read the Docs`__ at http://pg-query.readthedocs.io/en/latest/
        
        __ https://readthedocs.org/
        
        
        .. [*] This is an approximation, because in principle a list could contain different kinds of
               nodes, or even sub-lists in some cases: the ``List`` representation arbitrarily shows
               the tag of the first object.
        
        .. [*] Currently this covers most `DML` statements such as ``SELECT``\ s, ``INSERT``\ s,
               ``DELETE``\ s and ``UPDATE``\ s, fulfilling my needs, but I'd like to extend it to
               handle also `DDL` statements and, why not, `PLpgSQL` instructions too.
        
        
        .. -*- coding: utf-8 -*-
        
        Changes
        -------
        
        0.12 (2017-08-22)
        ~~~~~~~~~~~~~~~~~
        
        - New option ``--version`` on the command line tool
        
        - Better enums documentation
        
        - Release the GIL while calling libpg_query functions
        
        
        0.11 (2017-08-11)
        ~~~~~~~~~~~~~~~~~
        
        - Nicer indentation for JOINs, making OUTER JOINs stand out
        
        - Minor tweaks to lists rendering, with less spurious whitespaces
        
        - New option ``--no-location`` on the command line tool
        
        
        0.10 (2017-08-11)
        ~~~~~~~~~~~~~~~~~
        
        - Support Python 3.4 and Python 3.5 as well as Python 3.6
        
        
        0.9 (2017-08-10)
        ~~~~~~~~~~~~~~~~
        
        - Fix spacing before the $ character
        
        - Handle type modifiers
        
        - New option ``--plpgsql`` on the command line tool, just for fun
        
        
        0.8 (2017-08-10)
        ~~~~~~~~~~~~~~~~
        
        - Add enums subpackages to the documentation with references to their related headers
        
        - New ``compact_lists_margin`` option to produce a more compact representation when possible
          (see `issue #1`__)
        
        __ https://github.com/lelit/pg_query/issues/1
        
        
        0.7 (2017-08-10)
        ~~~~~~~~~~~~~~~~
        
        - Fix sdist including the Sphinx documentation
        
        
        0.6 (2017-08-10)
        ~~~~~~~~~~~~~~~~
        
        - New option ``--parse-tree`` on the command line tool to show just the parse tree
        
        - Sphinx documentation, available online
        
        
        0.5 (2017-08-09)
        ~~~~~~~~~~~~~~~~
        
        - Handle some more cases when a name must be double-quoted
        
        - Complete the serialization of the WindowDef node, handling its frame options
        
        
        0.4 (2017-08-09)
        ~~~~~~~~~~~~~~~~
        
        - Expose the actual PostgreSQL version the underlying libpg_query libray is built on thru a new
          ``get_postgresql_version()`` function
        
        - New option `safety_belt` for the ``prettify()`` function, to protect the innocents
        
        - Handle serialization of ``CoalesceExpr`` and ``MinMaxExpr``
        
        
        0.3 (2017-08-07)
        ~~~~~~~~~~~~~~~~
        
        - Handle serialization of ``ParamRef`` nodes
        
        - Expose a ``prettify()`` helper function
        
        
        0.2 (2017-08-07)
        ~~~~~~~~~~~~~~~~
        
        - Test coverage at 99%
        
        - First attempt at automatic wheel upload to PyPI, let's see...
        
        
        0.1 (2017-08-07)
        ~~~~~~~~~~~~~~~~
        
        - First release ("Hi daddy!", as my soul would tag it)
        
Platform: UNKNOWN
Classifier: Development Status :: 3 - Alpha
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3 :: Only
Classifier: Programming Language :: Python :: 3.4
Classifier: Programming Language :: Python :: 3.5
Classifier: Programming Language :: Python :: 3.6
Classifier: Programming Language :: SQL
Classifier: Topic :: Database
Classifier: Topic :: Utilities
