psycopg2/lib/extras.py

"""Miscellaneous goodies for psycopg2

This module is a generic place used to hold little helper functions
and classes untill a better place in the distribution is found.
"""
# psycopg/extras.py - miscellaneous extra goodies for psycopg
#
# Copyright (C) 2003-2004 Federico Di Gregorio  <fog@debian.org>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by the
# Free Software Foundation; either version 2, or (at your option) any later
# version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY
# or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
# for more details.

import os
import time
import re as regex

try:
    import logging
except:
    logging = None

from psycopg2 import DATETIME, DataError
from psycopg2 import extensions as _ext
from psycopg2.extensions import cursor as _cursor
from psycopg2.extensions import connection as _connection
from psycopg2.extensions import adapt as _A


class DictCursorBase(_cursor):
    """Base class for all dict-like cursors."""

    def __init__(self, *args, **kwargs):
        if kwargs.has_key('row_factory'):
            row_factory = kwargs['row_factory']
            del kwargs['row_factory']
        else:
            raise NotImplementedError(
                "DictCursorBase can't be instantiated without a row factory.")
        _cursor.__init__(self, *args, **kwargs)
        self._query_executed = 0
        self._prefetch = 0
        self.row_factory = row_factory

    def fetchone(self):
        if self._prefetch:
            res = _cursor.fetchone(self)
        if self._query_executed:
            self._build_index()
        if not self._prefetch:
            res = _cursor.fetchone(self)
        return res

    def fetchmany(self, size=None):
        if self._prefetch:
            res = _cursor.fetchmany(self, size)
        if self._query_executed:
            self._build_index()
        if not self._prefetch:
            res = _cursor.fetchmany(self, size)
        return res

    def fetchall(self):
        if self._prefetch:
            res = _cursor.fetchall(self)
        if self._query_executed:
            self._build_index()
        if not self._prefetch:
            res = _cursor.fetchall(self)
        return res

    def next(self):
        if self._prefetch:
            res = _cursor.fetchone(self)
            if res is None:
                raise StopIteration()
        if self._query_executed:
            self._build_index()
        if not self._prefetch:
            res = _cursor.fetchone(self)
            if res is None:
                raise StopIteration()
        return res

class DictConnection(_connection):
    """A connection that uses DictCursor automatically."""
    def cursor(self, name=None):
        if name is None:
            return _connection.cursor(self, cursor_factory=DictCursor)
        else:
            return _connection.cursor(self, name, cursor_factory=DictCursor)

class DictCursor(DictCursorBase):
    """A cursor that keeps a list of column name -> index mappings."""

    def __init__(self, *args, **kwargs):
        kwargs['row_factory'] = DictRow
        DictCursorBase.__init__(self, *args, **kwargs)
        self._prefetch = 1

    def execute(self, query, vars=None, async=0):
        self.index = {}
        self._query_executed = 1
        return _cursor.execute(self, query, vars, async)

    def callproc(self, procname, vars=None):
        self.index = {}
        self._query_executed = 1
        return _cursor.callproc(self, procname, vars)

    def _build_index(self):
        if self._query_executed == 1 and self.description:
            for i in range(len(self.description)):
                self.index[self.description[i][0]] = i
            self._query_executed = 0

class DictRow(list):
    """A row object that allow by-colun-name access to data."""

    __slots__ = ('_index',)

    def __init__(self, cursor):
        self._index = cursor.index
        self[:] = [None] * len(cursor.description)

    def __getitem__(self, x):
        if type(x) != int:
            x = self._index[x]
        return list.__getitem__(self, x)

    def items(self):
        res = []
        for n, v in self._index.items():
            res.append((n, list.__getitem__(self, v)))
        return res

    def keys(self):
        return self._index.keys()

    def values(self):
        return tuple(self[:])

    def has_key(self, x):
        return self._index.has_key(x)

    def get(self, x, default=None):
        try:
            return self[x]
        except:
            return default

    def iteritems(self):
        for n, v in self._index.items():
            yield n, list.__getitem__(self, v)

    def iterkeys(self):
        return self._index.iterkeys()

    def itervalues(self):
        return list.__iter__(self)

    def copy(self):
        return dict(self.items())

    def __contains__(self, x):
        return self._index.__contains__(x)

class RealDictConnection(_connection):
    """A connection that uses RealDictCursor automatically."""
    def cursor(self, name=None):
        if name is None:
            return _connection.cursor(self, cursor_factory=RealDictCursor)
        else:
            return _connection.cursor(self, name, cursor_factory=RealDictCursor)

class RealDictCursor(DictCursorBase):
    """A cursor that uses a real dict as the base type for rows.

    Note that this cursor is extremely specialized and does not allow
    the normal access (using integer indices) to fetched data. If you need
    to access database rows both as a dictionary and a list, then use
    the generic DictCursor instead of RealDictCursor.
    """

    def __init__(self, *args, **kwargs):
        kwargs['row_factory'] = RealDictRow
        DictCursorBase.__init__(self, *args, **kwargs)
        self._prefetch = 0

    def execute(self, query, vars=None, async=0):
        self.column_mapping = []
        self._query_executed = 1
        return _cursor.execute(self, query, vars, async)

    def callproc(self, procname, vars=None):
        self.column_mapping = []
        self._query_executed = 1
        return _cursor.callproc(self, procname, vars)

    def _build_index(self):
        if self._query_executed == 1 and self.description:
            for i in range(len(self.description)):
                self.column_mapping.append(self.description[i][0])
            self._query_executed = 0

class RealDictRow(dict):

    __slots__ = ('_column_mapping')

    def __init__(self, cursor):
        dict.__init__(self)
        self._column_mapping = cursor.column_mapping

    def __setitem__(self, name, value):
        if type(name) == int:
            name = self._column_mapping[name]
        return dict.__setitem__(self, name, value)


class LoggingConnection(_connection):
    """A connection that logs all queries to a file or logger object."""

    def initialize(self, logobj):
        """Initialize the connection to log to `logobj`.

        The `logobj` parameter can be an open file object or a Logger instance
        from the standard logging module.
        """
        self._logobj = logobj
        if logging and isinstance(logobj, logging.Logger):
            self.log = self._logtologger
        else:
            self.log = self._logtofile
    
    def filter(self, msg, curs):
        """Filter the query before logging it.

        This is the method to overwrite to filter unwanted queries out of the
        log or to add some extra data to the output. The default implementation
        just does nothing.
        """
        return msg
    
    def _logtofile(self, msg, curs):
        msg = self.filter(msg, curs)
        if msg: self._logobj.write(msg + os.linesep)
        
    def _logtologger(self, msg, curs):
        msg = self.filter(msg, curs)
        if msg: self._logobj.debug(msg)
    
    def _check(self):
        if not hasattr(self, '_logobj'):
            raise self.ProgrammingError(
                "LoggingConnection object has not been initialize()d")
            
    def cursor(self, name=None):
        self._check()
        if name is None:
            return _connection.cursor(self, cursor_factory=LoggingCursor)
        else:
            return _connection.cursor(self, name, cursor_factory=LoggingCursor)

class LoggingCursor(_cursor):
    """A cursor that logs queries using its connection logging facilities."""

    def execute(self, query, vars=None, async=0):
        try:
            return _cursor.execute(self, query, vars, async)
        finally:
            self.connection.log(self.query, self)

    def callproc(self, procname, vars=None):
        try:
            return _cursor.callproc(self, procname, vars)  
        finally:
            self.connection.log(self.query, self)


class MinTimeLoggingConnection(LoggingConnection):
    """A connection that logs queries based on execution time.
    
    This is just an example of how to sub-class LoggingConnection to provide
    some extra filtering for the logged queries. Both the `.inizialize()` and
    `.filter()` methods are overwritten to make sure that only queries
    executing for more than `mintime` ms are logged.
    
    Note that this connection uses the specialized cursor MinTimeLoggingCursor.
    """
    def initialize(self, logobj, mintime=0):
        LoggingConnection.initialize(self, logobj)
        self._mintime = mintime

    def filter(self, msg, curs):
        t = (time.time() - curs.timestamp) * 1000
        if t > self._mintime:
            return msg + os.linesep + "  (execution time: %d ms)" % t

    def cursor(self, name=None):
        self._check()
        if name is None:
            return _connection.cursor(self, cursor_factory=MinTimeLoggingCursor)
        else:
            return _connection.cursor(self, name, cursor_factory=MinTimeLoggingCursor)
    
class MinTimeLoggingCursor(LoggingCursor):
    """The cursor sub-class companion to MinTimeLoggingConnection."""

    def execute(self, query, vars=None, async=0):
        self.timestamp = time.time()
        return LoggingCursor.execute(self, query, vars, async)
    
    def callproc(self, procname, vars=None):
        self.timestamp = time.time()
        return LoggingCursor.execute(self, procname, vars)


# a dbtype and adapter for Python UUID type

try:
    import uuid

    class UUID_adapter(object):
        """Adapt Python's uuid.UUID type to PostgreSQL's uuid."""
        
        def __init__(self, uuid):
            self._uuid = uuid
    
        def prepare(self, conn):
            pass
        
        def getquoted(self):
            return "'"+str(self._uuid)+"'::uuid"
            
        __str__ = getquoted

    def register_uuid(oid=None, conn_or_curs=None):
        """Create the UUID type and an uuid.UUID adapter."""
        if not oid: oid = 2950
        _ext.UUID = _ext.new_type((oid, ), "UUID",
                lambda data, cursor: data and uuid.UUID(data) or None)
        _ext.register_type(_ext.UUID, conn_or_curs)
        _ext.register_adapter(uuid.UUID, UUID_adapter)
        return _ext.UUID

except ImportError, e:
    def register_uuid(oid=None):
        """Create the UUID type and an uuid.UUID adapter.

        This is a fake function that will always raise an error because the
        import of the uuid module failed.
        """
        raise e


# a type, dbtype and adapter for PostgreSQL inet type

class Inet(object):
    """Wrap a string to allow for correct SQL-quoting of inet values.

    Note that this adapter does NOT check the passed value to make
    sure it really is an inet-compatible address but DOES call adapt()
    on it to make sure it is impossible to execute an SQL-injection
    by passing an evil value to the initializer.
    """
    def __init__(self, addr):
        self.addr
    
    def prepare(self, conn):
        self._conn = conn
    
    def getquoted(self):
        obj = adapt(self.addr)
        if hasattr(obj, 'prepare'):
            obj.prepare(self._conn)
        return obj.getquoted()+"::inet"

    def __str__(self):
        return str(self.addr)
        
def register_inet(oid=None, conn_or_curs=None):
    """Create the INET type and an Inet adapter."""
    if not oid: oid = 869
    _ext.INET = _ext.new_type((oid, ), "INET",
            lambda data, cursor: data and Inet(data) or None)
    _ext.register_type(_ext.INET, conn_or_curs)
    return _ext.INET


# safe management of times with a non-standard time zone

def _convert_tstz_w_secs(s, cursor):
    try:
        return DATETIME(s, cursor)
        
    except (DataError,), exc:
        if exc.message != "unable to parse time":
                raise

        if regex.match('(\+|-)\d\d:\d\d:\d\d', s[-9:]) is None:
                raise

        # parsing doesn't succeed even if seconds are ":00" so truncate in
        # any case
        return DATETIME(s[:-3], cursor)

def register_tstz_w_secs(oids=None, conn_or_curs=None):
    """Register alternate type caster for TIMESTAMP WITH TIME ZONE.

    The Python datetime module cannot handle time zones with
    seconds in the UTC offset. There are, however, historical
    "time zones" which contain such offsets, eg. "Asia/Calcutta".
    In many cases those offsets represent true local time.

    If you encounter "unable to parse time" on a perfectly valid
    timestamp you likely want to try this type caster. It truncates
    the seconds from the time zone data and retries casting
    the timestamp. Note that this will generate timestamps
    which are INACCURATE by the number of seconds truncated
    (unless the seconds were 00).

    <oids>
            which OIDs to use this type caster for,
            defaults to TIMESTAMP WITH TIME ZONE
    <conn_or_curs>
            a cursor or connection if you want to attach
            this type caster to that only, defaults to
            None meaning all connections and cursors
    """
    if oids is None:
        oids = (1184,) # hardcoded from PostgreSQL headers

    _ext.TSTZ_W_SECS = _ext.new_type(oids, 'TSTZ_W_SECS', _convert_tstz_w_secs)
    _ext.register_type(TSTZ_W_SECS, conn_or_curs)

    return _ext.TSTZ_W_SECS


__all__ = [ k for k in locals().keys() if not k.startswith('_') ]