"""
SQL composition utility module
"""
# Copyright (C) 2020 The Psycopg Team
from __future__ import annotations
import codecs
import string
from abc import ABC, abstractmethod
from typing import Any, Iterator, Iterable, Sequence
from .pq import Escaping
from .abc import AdaptContext
from ._enums import PyFormat
from ._compat import LiteralString
from ._encodings import conn_encoding
from ._transformer import Transformer
def quote(obj: Any, context: AdaptContext | None = None) -> str:
"""
Adapt a Python object to a quoted SQL string.
Use this function only if you absolutely want to convert a Python string to
an SQL quoted literal to use e.g. to generate batch SQL and you won't have
a connection available when you will need to use it.
This function is relatively inefficient, because it doesn't cache the
adaptation rules. If you pass a `!context` you can adapt the adaptation
rules used, otherwise only global rules are used.
"""
return Literal(obj).as_string(context)
class Composable(ABC):
"""
Abstract base class for objects that can be used to compose an SQL 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.
`!SQL` and `!Composed` objects can be passed directly to
`~psycopg.Cursor.execute()`, `~psycopg.Cursor.executemany()`,
`~psycopg.Cursor.copy()` in place of the query string.
"""
def __init__(self, obj: Any):
self._obj = obj
def __repr__(self) -> str:
return f"{self.__class__.__name__}({self._obj!r})"
@abstractmethod
def as_bytes(self, context: AdaptContext | None = None) -> bytes:
"""
Return the value of the object as bytes.
:param context: the context to evaluate the object into.
:type context: `connection` or `cursor`
The method is automatically invoked by `~psycopg.Cursor.execute()`,
`~psycopg.Cursor.executemany()`, `~psycopg.Cursor.copy()` if a
`!Composable` is passed instead of the query string.
"""
raise NotImplementedError
def as_string(self, context: AdaptContext | None = None) -> str:
"""
Return the value of the object as string.
:param context: the context to evaluate the string into.
:type context: `connection` or `cursor`
"""
conn = context.connection if context else None
enc = conn_encoding(conn)
b = self.as_bytes(context)
if isinstance(b, bytes):
return b.decode(enc)
else:
# buffer object
return codecs.lookup(enc).decode(b)[0]
def __add__(self, other: Composable) -> Composed:
if isinstance(other, Composed):
return Composed([self]) + other
if isinstance(other, Composable):
return Composed([self]) + Composed([other])
else:
return NotImplemented
def __mul__(self, n: int) -> Composed:
return Composed([self] * n)
def __eq__(self, other: Any) -> bool:
return type(self) is type(other) and self._obj == other._obj
def __ne__(self, other: Any) -> bool:
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
(such as the `SQL.format()` method). `!Composed` objects can be passed
directly to `~psycopg.Cursor.execute()`, `~psycopg.Cursor.executemany()`,
`~psycopg.Cursor.copy()` in place of the query string.
It is also possible to create a `!Composed` directly specifying a sequence
of objects as arguments: if they are not `!Composable` they will be wrapped
in a `Literal`.
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).
"""
_obj: list[Composable]
def __init__(self, seq: Sequence[Any]):
seq = [obj if isinstance(obj, Composable) else Literal(obj) for obj in seq]
super().__init__(seq)
def as_bytes(self, context: AdaptContext | None = None) -> bytes:
return b"".join(obj.as_bytes(context) for obj in self._obj)
def __iter__(self) -> Iterator[Composable]:
return iter(self._obj)
def __add__(self, other: Composable) -> Composed:
if isinstance(other, Composed):
return Composed(self._obj + other._obj)
if isinstance(other, Composable):
return Composed(self._obj + [other])
else:
return NotImplemented
def join(self, joiner: SQL | LiteralString) -> Composed:
"""
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 strings or SQL,"
f" got {joiner!r} instead"
)
return joiner.join(self._obj)
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 `!obj` 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.
`!SQL` objects can be passed directly to `~psycopg.Cursor.execute()`,
`~psycopg.Cursor.executemany()`, `~psycopg.Cursor.copy()` in place of the
query string.
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"
"""
_obj: LiteralString
_formatter = string.Formatter()
def __init__(self, obj: LiteralString):
super().__init__(obj)
if not isinstance(obj, str):
raise TypeError(f"SQL values must be strings, got {obj!r} instead")
def as_string(self, context: AdaptContext | None = None) -> str:
return self._obj
def as_bytes(self, context: AdaptContext | None = None) -> bytes:
conn = context.connection if context else None
enc = conn_encoding(conn)
return self._obj.encode(enc)
def format(self, *args: Any, **kwargs: Any) -> Composed:
"""
Merge `Composable` objects into a template.
:param args: parameters to replace to numbered (``{0}``, ``{1}``) or
auto-numbered (``{}``) placeholders
:param 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.
If a `!Composable` objects is passed to the template it will be merged
according to its `as_string()` method. If any other Python object is
passed, it will be wrapped in a `Literal` object and so escaped
according to SQL rules.
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 name = {name}")
... .format(tbl=sql.Identifier('people'), name="O'Rourke"))
... .as_string(conn))
SELECT * FROM "people" WHERE name = 'O''Rourke'
"""
rv: list[Composable] = []
autonum: int | None = 0
# TODO: this is probably not the right way to whitelist pre
# pyre complains. Will wait for mypy to complain too to fix.
pre: LiteralString
for pre, name, spec, conv in self._formatter.parse(self._obj):
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: Iterable[Composable]) -> Composed:
"""
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/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"
"""
_obj: Sequence[str]
def __init__(self, *strings: str):
# init super() now to make the __repr__ not explode in case of error
super().__init__(strings)
if not strings:
raise TypeError("Identifier cannot be empty")
for s in strings:
if not isinstance(s, str):
raise TypeError(
f"SQL identifier parts must be strings, got {s!r} instead"
)
def __repr__(self) -> str:
return f"{self.__class__.__name__}({', '.join(map(repr, self._obj))})"
def as_bytes(self, context: AdaptContext | None = None) -> bytes:
conn = context.connection if context else None
if conn:
esc = Escaping(conn.pgconn)
enc = conn_encoding(conn)
escs = [esc.escape_identifier(s.encode(enc)) for s in self._obj]
else:
escs = [self._escape_identifier(s.encode()) for s in self._obj]
return b".".join(escs)
def _escape_identifier(self, s: bytes) -> bytes:
"""
Approximation of PQescapeIdentifier taking no connection.
"""
return b'"' + s.replace(b'"', b'""') + b'"'
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 <types-adaptation>` for Python objects.
Example::
>>> s1 = sql.Literal("fo'o")
>>> s2 = sql.Literal(42)
>>> s3 = sql.Literal(date(2000, 1, 1))
>>> print(sql.SQL(', ').join([s1, s2, s3]).as_string(conn))
'fo''o', 42, '2000-01-01'::date
"""
def as_bytes(self, context: AdaptContext | None = None) -> bytes:
tx = Transformer.from_context(context)
return tx.as_literal(self._obj)
class Placeholder(Composable):
"""A `Composable` representing a placeholder for query parameters.
If the name is specified, generate a named placeholder (e.g. ``%(name)s``,
``%(name)b``), otherwise generate a positional placeholder (e.g. ``%s``,
``%b``).
The object is useful to generate SQL queries with a variable number of
arguments.
Examples::
>>> names = ['foo', 'bar', 'baz']
>>> q1 = sql.SQL("INSERT INTO my_table ({}) VALUES ({})").format(
... sql.SQL(', ').join(map(sql.Identifier, names)),
... sql.SQL(', ').join(sql.Placeholder() * len(names)))
>>> print(q1.as_string(conn))
INSERT INTO my_table ("foo", "bar", "baz") VALUES (%s, %s, %s)
>>> q2 = sql.SQL("INSERT INTO my_table ({}) VALUES ({})").format(
... sql.SQL(', ').join(map(sql.Identifier, names)),
... sql.SQL(', ').join(map(sql.Placeholder, names)))
>>> print(q2.as_string(conn))
INSERT INTO my_table ("foo", "bar", "baz") VALUES (%(foo)s, %(bar)s, %(baz)s)
"""
def __init__(self, name: str = "", format: str | PyFormat = PyFormat.AUTO):
super().__init__(name)
if not isinstance(name, str):
raise TypeError(f"expected string as name, got {name!r}")
if ")" in name:
raise ValueError(f"invalid name: {name!r}")
if type(format) is str:
format = PyFormat(format)
if not isinstance(format, PyFormat):
raise TypeError(
f"expected PyFormat as format, got {type(format).__name__!r}"
)
self._format: PyFormat = format
def __repr__(self) -> str:
parts = []
if self._obj:
parts.append(repr(self._obj))
if self._format is not PyFormat.AUTO:
parts.append(f"format={self._format.name}")
return f"{self.__class__.__name__}({', '.join(parts)})"
def as_string(self, context: AdaptContext | None = None) -> str:
code = self._format.value
return f"%({self._obj}){code}" if self._obj else f"%{code}"
def as_bytes(self, context: AdaptContext | None = None) -> bytes:
conn = context.connection if context else None
enc = conn_encoding(conn)
return self.as_string(context).encode(enc)
# Literals
NULL = SQL("NULL")
DEFAULT = SQL("DEFAULT")