456 lines
14 KiB
Python
456 lines
14 KiB
Python
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"""SQL composition utility module
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"""
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# psycopg/sql.py - SQL composition utility module
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#
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# Copyright (C) 2016-2019 Daniele Varrazzo <daniele.varrazzo@gmail.com>
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#
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# psycopg2 is free software: you can redistribute it and/or modify it
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# under the terms of the GNU Lesser General Public License as published
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# by the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# In addition, as a special exception, the copyright holders give
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# permission to link this program with the OpenSSL library (or with
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# modified versions of OpenSSL that use the same license as OpenSSL),
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# and distribute linked combinations including the two.
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#
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# You must obey the GNU Lesser General Public License in all respects for
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# all of the code used other than OpenSSL.
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#
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# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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# License for more details.
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import string
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from psycopg2 import extensions as ext
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from psycopg2.compat import PY3, string_types
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_formatter = string.Formatter()
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class Composable(object):
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"""
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Abstract base class for objects that can be used to compose an SQL string.
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`!Composable` objects can be passed directly to `~cursor.execute()`,
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`~cursor.executemany()`, `~cursor.copy_expert()` in place of the query
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string.
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`!Composable` objects can be joined using the ``+`` operator: the result
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will be a `Composed` instance containing the objects joined. The operator
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``*`` is also supported with an integer argument: the result is a
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`!Composed` instance containing the left argument repeated as many times as
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requested.
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"""
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def __init__(self, wrapped):
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self._wrapped = wrapped
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def __repr__(self):
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return "%s(%r)" % (self.__class__.__name__, self._wrapped)
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def as_string(self, context):
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"""
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Return the string value of the object.
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:param context: the context to evaluate the string into.
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:type context: `connection` or `cursor`
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The method is automatically invoked by `~cursor.execute()`,
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`~cursor.executemany()`, `~cursor.copy_expert()` if a `!Composable` is
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passed instead of the query string.
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"""
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raise NotImplementedError
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def __add__(self, other):
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if isinstance(other, Composed):
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return Composed([self]) + other
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if isinstance(other, Composable):
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return Composed([self]) + Composed([other])
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else:
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return NotImplemented
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def __mul__(self, n):
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return Composed([self] * n)
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def __eq__(self, other):
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return type(self) is type(other) and self._wrapped == other._wrapped
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def __ne__(self, other):
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return not self.__eq__(other)
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class Composed(Composable):
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"""
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A `Composable` object made of a sequence of `!Composable`.
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The object is usually created using `!Composable` operators and methods.
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However it is possible to create a `!Composed` directly specifying a
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sequence of `!Composable` as arguments.
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Example::
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>>> comp = sql.Composed(
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... [sql.SQL("insert into "), sql.Identifier("table")])
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>>> print(comp.as_string(conn))
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insert into "table"
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`!Composed` objects are iterable (so they can be used in `SQL.join` for
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instance).
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"""
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def __init__(self, seq):
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wrapped = []
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for i in seq:
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if not isinstance(i, Composable):
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raise TypeError(
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"Composed elements must be Composable, got %r instead" % i)
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wrapped.append(i)
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super(Composed, self).__init__(wrapped)
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@property
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def seq(self):
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"""The list of the content of the `!Composed`."""
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return list(self._wrapped)
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def as_string(self, context):
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rv = []
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for i in self._wrapped:
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rv.append(i.as_string(context))
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return ''.join(rv)
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def __iter__(self):
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return iter(self._wrapped)
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def __add__(self, other):
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if isinstance(other, Composed):
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return Composed(self._wrapped + other._wrapped)
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if isinstance(other, Composable):
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return Composed(self._wrapped + [other])
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else:
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return NotImplemented
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def join(self, joiner):
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"""
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Return a new `!Composed` interposing the *joiner* with the `!Composed` items.
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The *joiner* must be a `SQL` or a string which will be interpreted as
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an `SQL`.
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Example::
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>>> fields = sql.Identifier('foo') + sql.Identifier('bar') # a Composed
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>>> print(fields.join(', ').as_string(conn))
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"foo", "bar"
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"""
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if isinstance(joiner, string_types):
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joiner = SQL(joiner)
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elif not isinstance(joiner, SQL):
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raise TypeError(
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"Composed.join() argument must be a string or an SQL")
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return joiner.join(self)
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class SQL(Composable):
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"""
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A `Composable` representing a snippet of SQL statement.
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`!SQL` exposes `join()` and `format()` methods useful to create a template
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where to merge variable parts of a query (for instance field or table
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names).
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The *string* doesn't undergo any form of escaping, so it is not suitable to
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represent variable identifiers or values: you should only use it to pass
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constant strings representing templates or snippets of SQL statements; use
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other objects such as `Identifier` or `Literal` to represent variable
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parts.
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Example::
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>>> query = sql.SQL("select {0} from {1}").format(
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... sql.SQL(', ').join([sql.Identifier('foo'), sql.Identifier('bar')]),
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... sql.Identifier('table'))
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>>> print(query.as_string(conn))
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select "foo", "bar" from "table"
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"""
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def __init__(self, string):
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if not isinstance(string, string_types):
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raise TypeError("SQL values must be strings")
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super(SQL, self).__init__(string)
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@property
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def string(self):
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"""The string wrapped by the `!SQL` object."""
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return self._wrapped
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def as_string(self, context):
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return self._wrapped
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def format(self, *args, **kwargs):
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"""
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Merge `Composable` objects into a template.
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:param `Composable` args: parameters to replace to numbered
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(``{0}``, ``{1}``) or auto-numbered (``{}``) placeholders
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:param `Composable` kwargs: parameters to replace to named (``{name}``)
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placeholders
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:return: the union of the `!SQL` string with placeholders replaced
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:rtype: `Composed`
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The method is similar to the Python `str.format()` method: the string
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template supports auto-numbered (``{}``), numbered (``{0}``,
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``{1}``...), and named placeholders (``{name}``), with positional
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arguments replacing the numbered placeholders and keywords replacing
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the named ones. However placeholder modifiers (``{0!r}``, ``{0:<10}``)
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are not supported. Only `!Composable` objects can be passed to the
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template.
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Example::
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>>> print(sql.SQL("select * from {} where {} = %s")
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... .format(sql.Identifier('people'), sql.Identifier('id'))
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... .as_string(conn))
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select * from "people" where "id" = %s
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>>> print(sql.SQL("select * from {tbl} where {pkey} = %s")
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... .format(tbl=sql.Identifier('people'), pkey=sql.Identifier('id'))
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... .as_string(conn))
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select * from "people" where "id" = %s
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"""
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rv = []
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autonum = 0
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for pre, name, spec, conv in _formatter.parse(self._wrapped):
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if spec:
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raise ValueError("no format specification supported by SQL")
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if conv:
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raise ValueError("no format conversion supported by SQL")
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if pre:
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rv.append(SQL(pre))
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if name is None:
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continue
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if name.isdigit():
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if autonum:
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raise ValueError(
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"cannot switch from automatic field numbering to manual")
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rv.append(args[int(name)])
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autonum = None
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elif not name:
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if autonum is None:
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raise ValueError(
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"cannot switch from manual field numbering to automatic")
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rv.append(args[autonum])
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autonum += 1
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else:
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rv.append(kwargs[name])
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return Composed(rv)
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def join(self, seq):
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"""
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Join a sequence of `Composable`.
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:param seq: the elements to join.
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:type seq: iterable of `!Composable`
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Use the `!SQL` object's *string* to separate the elements in *seq*.
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Note that `Composed` objects are iterable too, so they can be used as
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argument for this method.
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Example::
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>>> snip = sql.SQL(', ').join(
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... sql.Identifier(n) for n in ['foo', 'bar', 'baz'])
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>>> print(snip.as_string(conn))
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"foo", "bar", "baz"
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"""
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rv = []
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it = iter(seq)
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try:
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rv.append(next(it))
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except StopIteration:
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pass
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else:
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for i in it:
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rv.append(self)
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rv.append(i)
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return Composed(rv)
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class Identifier(Composable):
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"""
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A `Composable` representing an SQL identifier or a dot-separated sequence.
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Identifiers usually represent names of database objects, such as tables or
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fields. PostgreSQL identifiers follow `different rules`__ than SQL string
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literals for escaping (e.g. they use double quotes instead of single).
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.. __: https://www.postgresql.org/docs/current/static/sql-syntax-lexical.html# \
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SQL-SYNTAX-IDENTIFIERS
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Example::
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>>> t1 = sql.Identifier("foo")
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>>> t2 = sql.Identifier("ba'r")
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>>> t3 = sql.Identifier('ba"z')
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>>> print(sql.SQL(', ').join([t1, t2, t3]).as_string(conn))
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"foo", "ba'r", "ba""z"
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Multiple strings can be passed to the object to represent a qualified name,
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i.e. a dot-separated sequence of identifiers.
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Example::
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>>> query = sql.SQL("select {} from {}").format(
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... sql.Identifier("table", "field"),
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... sql.Identifier("schema", "table"))
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>>> print(query.as_string(conn))
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select "table"."field" from "schema"."table"
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"""
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def __init__(self, *strings):
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if not strings:
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raise TypeError("Identifier cannot be empty")
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for s in strings:
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if not isinstance(s, string_types):
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raise TypeError("SQL identifier parts must be strings")
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super(Identifier, self).__init__(strings)
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@property
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def strings(self):
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"""A tuple with the strings wrapped by the `Identifier`."""
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return self._wrapped
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@property
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def string(self):
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"""The string wrapped by the `Identifier`.
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"""
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if len(self._wrapped) == 1:
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return self._wrapped[0]
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else:
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raise AttributeError(
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"the Identifier wraps more than one than one string")
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def __repr__(self):
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return "%s(%s)" % (
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self.__class__.__name__,
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', '.join(map(repr, self._wrapped)))
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def as_string(self, context):
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return '.'.join(ext.quote_ident(s, context) for s in self._wrapped)
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class Literal(Composable):
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"""
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A `Composable` representing an SQL value to include in a query.
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Usually you will want to include placeholders in the query and pass values
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as `~cursor.execute()` arguments. If however you really really need to
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include a literal value in the query you can use this object.
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The string returned by `!as_string()` follows the normal :ref:`adaptation
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rules <python-types-adaptation>` for Python objects.
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Example::
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>>> s1 = sql.Literal("foo")
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>>> s2 = sql.Literal("ba'r")
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>>> s3 = sql.Literal(42)
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>>> print(sql.SQL(', ').join([s1, s2, s3]).as_string(conn))
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'foo', 'ba''r', 42
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"""
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@property
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def wrapped(self):
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"""The object wrapped by the `!Literal`."""
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return self._wrapped
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def as_string(self, context):
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# is it a connection or cursor?
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if isinstance(context, ext.connection):
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conn = context
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elif isinstance(context, ext.cursor):
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conn = context.connection
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else:
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raise TypeError("context must be a connection or a cursor")
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a = ext.adapt(self._wrapped)
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if hasattr(a, 'prepare'):
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a.prepare(conn)
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rv = a.getquoted()
|
||
|
|
if PY3 and isinstance(rv, bytes):
|
||
|
|
rv = rv.decode(ext.encodings[conn.encoding])
|
||
|
|
|
||
|
|
return rv
|
||
|
|
|
||
|
|
|
||
|
|
class Placeholder(Composable):
|
||
|
|
"""A `Composable` representing a placeholder for query parameters.
|
||
|
|
|
||
|
|
If the name is specified, generate a named placeholder (e.g. ``%(name)s``),
|
||
|
|
otherwise generate a positional placeholder (e.g. ``%s``).
|
||
|
|
|
||
|
|
The object is useful to generate SQL queries with a variable number of
|
||
|
|
arguments.
|
||
|
|
|
||
|
|
Examples::
|
||
|
|
|
||
|
|
>>> names = ['foo', 'bar', 'baz']
|
||
|
|
|
||
|
|
>>> q1 = sql.SQL("insert into table ({}) values ({})").format(
|
||
|
|
... sql.SQL(', ').join(map(sql.Identifier, names)),
|
||
|
|
... sql.SQL(', ').join(sql.Placeholder() * len(names)))
|
||
|
|
>>> print(q1.as_string(conn))
|
||
|
|
insert into table ("foo", "bar", "baz") values (%s, %s, %s)
|
||
|
|
|
||
|
|
>>> q2 = sql.SQL("insert into table ({}) values ({})").format(
|
||
|
|
... sql.SQL(', ').join(map(sql.Identifier, names)),
|
||
|
|
... sql.SQL(', ').join(map(sql.Placeholder, names)))
|
||
|
|
>>> print(q2.as_string(conn))
|
||
|
|
insert into table ("foo", "bar", "baz") values (%(foo)s, %(bar)s, %(baz)s)
|
||
|
|
|
||
|
|
"""
|
||
|
|
|
||
|
|
def __init__(self, name=None):
|
||
|
|
if isinstance(name, string_types):
|
||
|
|
if ')' in name:
|
||
|
|
raise ValueError("invalid name: %r" % name)
|
||
|
|
|
||
|
|
elif name is not None:
|
||
|
|
raise TypeError("expected string or None as name, got %r" % name)
|
||
|
|
|
||
|
|
super(Placeholder, self).__init__(name)
|
||
|
|
|
||
|
|
@property
|
||
|
|
def name(self):
|
||
|
|
"""The name of the `!Placeholder`."""
|
||
|
|
return self._wrapped
|
||
|
|
|
||
|
|
def __repr__(self):
|
||
|
|
return "Placeholder(%r)" % (
|
||
|
|
self._wrapped if self._wrapped is not None else '',)
|
||
|
|
|
||
|
|
def as_string(self, context):
|
||
|
|
if self._wrapped is not None:
|
||
|
|
return "%%(%s)s" % self._wrapped
|
||
|
|
else:
|
||
|
|
return "%s"
|
||
|
|
|
||
|
|
|
||
|
|
# Literals
|
||
|
|
NULL = SQL("NULL")
|
||
|
|
DEFAULT = SQL("DEFAULT")
|