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"""SQL composition utility module
"""
# psycopg/sql.py - SQL composition utility module
#
# Copyright (C) 2016-2019 Daniele Varrazzo <daniele.varrazzo@gmail.com>
# Copyright (C) 2020-2021 The Psycopg Team
#
# 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
_formatter = string.Formatter()
class Composable:
"""
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 f"{self.__class__.__name__}({self._wrapped!r})"
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(
f"Composed elements must be Composable, got {i!r} instead")
wrapped.append(i)
super().__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, str):
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, str):
raise TypeError("SQL values must be strings")
super().__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, str):
raise TypeError("SQL identifier parts must be strings")
super().__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 f"{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 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, str):
if ')' in name:
raise ValueError(f"invalid name: {name!r}")
elif name is not None:
raise TypeError(f"expected string or None as name, got {name!r}")
super().__init__(name)
@property
def name(self):
"""The name of the `!Placeholder`."""
return self._wrapped
def __repr__(self):
if self._wrapped is None:
return f"{self.__class__.__name__}()"
else:
return f"{self.__class__.__name__}({self._wrapped!r})"
def as_string(self, context):
if self._wrapped is not None:
return f"%({self._wrapped})s"
else:
return "%s"
# Literals
NULL = SQL("NULL")
DEFAULT = SQL("DEFAULT")