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