/usr/lib/python2.7/dist-packages/sqlalchemy/orm/session.py is in python-sqlalchemy 0.8.4-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 | # orm/session.py
# Copyright (C) 2005-2013 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Provides the Session class and related utilities."""
from __future__ import with_statement
import weakref
from .. import util, sql, engine, exc as sa_exc, event
from ..sql import util as sql_util, expression
from . import (
SessionExtension, attributes, exc, query, util as orm_util,
loading, identity
)
from .util import (
object_mapper, class_mapper,
_class_to_mapper, _state_mapper, object_state,
_none_set
)
from .unitofwork import UOWTransaction
from .mapper import Mapper
from .events import SessionEvents
statelib = util.importlater("sqlalchemy.orm", "state")
import sys
__all__ = ['Session', 'SessionTransaction', 'SessionExtension', 'sessionmaker']
class _SessionClassMethods(object):
"""Class-level methods for :class:`.Session`, :class:`.sessionmaker`."""
@classmethod
def close_all(cls):
"""Close *all* sessions in memory."""
for sess in _sessions.values():
sess.close()
@classmethod
def identity_key(cls, *args, **kwargs):
"""Return an identity key.
This is an alias of :func:`.util.identity_key`.
"""
return orm_util.identity_key(*args, **kwargs)
@classmethod
def object_session(cls, instance):
"""Return the :class:`.Session` to which an object belongs.
This is an alias of :func:`.object_session`.
"""
return object_session(instance)
ACTIVE = util.symbol('ACTIVE')
PREPARED = util.symbol('PREPARED')
COMMITTED = util.symbol('COMMITTED')
DEACTIVE = util.symbol('DEACTIVE')
CLOSED = util.symbol('CLOSED')
class SessionTransaction(object):
"""A :class:`.Session`-level transaction.
:class:`.SessionTransaction` is a mostly behind-the-scenes object
not normally referenced directly by application code. It coordinates
among multiple :class:`.Connection` objects, maintaining a database
transaction for each one individually, committing or rolling them
back all at once. It also provides optional two-phase commit behavior
which can augment this coordination operation.
The :attr:`.Session.transaction` attribute of :class:`.Session`
refers to the current :class:`.SessionTransaction` object in use, if any.
A :class:`.SessionTransaction` is associated with a :class:`.Session`
in its default mode of ``autocommit=False`` immediately, associated
with no database connections. As the :class:`.Session` is called upon
to emit SQL on behalf of various :class:`.Engine` or :class:`.Connection`
objects, a corresponding :class:`.Connection` and associated
:class:`.Transaction` is added to a collection within the
:class:`.SessionTransaction` object, becoming one of the
connection/transaction pairs maintained by the
:class:`.SessionTransaction`.
The lifespan of the :class:`.SessionTransaction` ends when the
:meth:`.Session.commit`, :meth:`.Session.rollback` or
:meth:`.Session.close` methods are called. At this point, the
:class:`.SessionTransaction` removes its association with its parent
:class:`.Session`. A :class:`.Session` that is in ``autocommit=False``
mode will create a new :class:`.SessionTransaction` to replace it
immediately, whereas a :class:`.Session` that's in ``autocommit=True``
mode will remain without a :class:`.SessionTransaction` until the
:meth:`.Session.begin` method is called.
Another detail of :class:`.SessionTransaction` behavior is that it is
capable of "nesting". This means that the :meth:`.Session.begin` method
can be called while an existing :class:`.SessionTransaction` is already
present, producing a new :class:`.SessionTransaction` that temporarily
replaces the parent :class:`.SessionTransaction`. When a
:class:`.SessionTransaction` is produced as nested, it assigns itself to
the :attr:`.Session.transaction` attribute. When it is ended via
:meth:`.Session.commit` or :meth:`.Session.rollback`, it restores its
parent :class:`.SessionTransaction` back onto the
:attr:`.Session.transaction` attribute. The behavior is effectively a
stack, where :attr:`.Session.transaction` refers to the current head of
the stack.
The purpose of this stack is to allow nesting of
:meth:`.Session.rollback` or :meth:`.Session.commit` calls in context
with various flavors of :meth:`.Session.begin`. This nesting behavior
applies to when :meth:`.Session.begin_nested` is used to emit a
SAVEPOINT transaction, and is also used to produce a so-called
"subtransaction" which allows a block of code to use a
begin/rollback/commit sequence regardless of whether or not its enclosing
code block has begun a transaction. The :meth:`.flush` method, whether
called explicitly or via autoflush, is the primary consumer of the
"subtransaction" feature, in that it wishes to guarantee that it works
within in a transaction block regardless of whether or not the
:class:`.Session` is in transactional mode when the method is called.
See also:
:meth:`.Session.rollback`
:meth:`.Session.commit`
:meth:`.Session.begin`
:meth:`.Session.begin_nested`
:attr:`.Session.is_active`
:meth:`.SessionEvents.after_commit`
:meth:`.SessionEvents.after_rollback`
:meth:`.SessionEvents.after_soft_rollback`
"""
_rollback_exception = None
def __init__(self, session, parent=None, nested=False):
self.session = session
self._connections = {}
self._parent = parent
self.nested = nested
self._state = ACTIVE
if not parent and nested:
raise sa_exc.InvalidRequestError(
"Can't start a SAVEPOINT transaction when no existing "
"transaction is in progress")
if self.session._enable_transaction_accounting:
self._take_snapshot()
if self.session.dispatch.after_transaction_create:
self.session.dispatch.after_transaction_create(self.session, self)
@property
def is_active(self):
return self.session is not None and self._state is ACTIVE
def _assert_active(self, prepared_ok=False,
rollback_ok=False,
deactive_ok=False,
closed_msg="This transaction is closed"):
if self._state is COMMITTED:
raise sa_exc.InvalidRequestError(
"This session is in 'committed' state; no further "
"SQL can be emitted within this transaction."
)
elif self._state is PREPARED:
if not prepared_ok:
raise sa_exc.InvalidRequestError(
"This session is in 'prepared' state; no further "
"SQL can be emitted within this transaction."
)
elif self._state is DEACTIVE:
if not deactive_ok and not rollback_ok:
if self._rollback_exception:
raise sa_exc.InvalidRequestError(
"This Session's transaction has been rolled back "
"due to a previous exception during flush."
" To begin a new transaction with this Session, "
"first issue Session.rollback()."
" Original exception was: %s"
% self._rollback_exception
)
elif not deactive_ok:
raise sa_exc.InvalidRequestError(
"This Session's transaction has been rolled back "
"by a nested rollback() call. To begin a new "
"transaction, issue Session.rollback() first."
)
elif self._state is CLOSED:
raise sa_exc.ResourceClosedError(closed_msg)
@property
def _is_transaction_boundary(self):
return self.nested or not self._parent
def connection(self, bindkey, **kwargs):
self._assert_active()
bind = self.session.get_bind(bindkey, **kwargs)
return self._connection_for_bind(bind)
def _begin(self, nested=False):
self._assert_active()
return SessionTransaction(
self.session, self, nested=nested)
def _iterate_parents(self, upto=None):
if self._parent is upto:
return (self,)
else:
if self._parent is None:
raise sa_exc.InvalidRequestError(
"Transaction %s is not on the active transaction list" % (
upto))
return (self,) + self._parent._iterate_parents(upto)
def _take_snapshot(self):
if not self._is_transaction_boundary:
self._new = self._parent._new
self._deleted = self._parent._deleted
self._dirty = self._parent._dirty
self._key_switches = self._parent._key_switches
return
if not self.session._flushing:
self.session.flush()
self._new = weakref.WeakKeyDictionary()
self._deleted = weakref.WeakKeyDictionary()
self._dirty = weakref.WeakKeyDictionary()
self._key_switches = weakref.WeakKeyDictionary()
def _restore_snapshot(self, dirty_only=False):
assert self._is_transaction_boundary
for s in set(self._new).union(self.session._new):
self.session._expunge_state(s)
if s.key:
del s.key
for s, (oldkey, newkey) in self._key_switches.items():
self.session.identity_map.discard(s)
s.key = oldkey
self.session.identity_map.replace(s)
for s in set(self._deleted).union(self.session._deleted):
if s.deleted:
#assert s in self._deleted
del s.deleted
self.session._update_impl(s, discard_existing=True)
assert not self.session._deleted
for s in self.session.identity_map.all_states():
if not dirty_only or s.modified or s in self._dirty:
s._expire(s.dict, self.session.identity_map._modified)
def _remove_snapshot(self):
assert self._is_transaction_boundary
if not self.nested and self.session.expire_on_commit:
for s in self.session.identity_map.all_states():
s._expire(s.dict, self.session.identity_map._modified)
for s in self._deleted:
s.session_id = None
self._deleted.clear()
def _connection_for_bind(self, bind):
self._assert_active()
if bind in self._connections:
return self._connections[bind][0]
if self._parent:
conn = self._parent._connection_for_bind(bind)
if not self.nested:
return conn
else:
if isinstance(bind, engine.Connection):
conn = bind
if conn.engine in self._connections:
raise sa_exc.InvalidRequestError(
"Session already has a Connection associated for the "
"given Connection's Engine")
else:
conn = bind.contextual_connect()
if self.session.twophase and self._parent is None:
transaction = conn.begin_twophase()
elif self.nested:
transaction = conn.begin_nested()
else:
transaction = conn.begin()
self._connections[conn] = self._connections[conn.engine] = \
(conn, transaction, conn is not bind)
self.session.dispatch.after_begin(self.session, self, conn)
return conn
def prepare(self):
if self._parent is not None or not self.session.twophase:
raise sa_exc.InvalidRequestError(
"'twophase' mode not enabled, or not root transaction; "
"can't prepare.")
self._prepare_impl()
def _prepare_impl(self):
self._assert_active()
if self._parent is None or self.nested:
self.session.dispatch.before_commit(self.session)
stx = self.session.transaction
if stx is not self:
for subtransaction in stx._iterate_parents(upto=self):
subtransaction.commit()
if not self.session._flushing:
for _flush_guard in xrange(100):
if self.session._is_clean():
break
self.session.flush()
else:
raise exc.FlushError(
"Over 100 subsequent flushes have occurred within "
"session.commit() - is an after_flush() hook "
"creating new objects?")
if self._parent is None and self.session.twophase:
try:
for t in set(self._connections.values()):
t[1].prepare()
except:
with util.safe_reraise():
self.rollback()
self._state = PREPARED
def commit(self):
self._assert_active(prepared_ok=True)
if self._state is not PREPARED:
self._prepare_impl()
if self._parent is None or self.nested:
for t in set(self._connections.values()):
t[1].commit()
self._state = COMMITTED
self.session.dispatch.after_commit(self.session)
if self.session._enable_transaction_accounting:
self._remove_snapshot()
self.close()
return self._parent
def rollback(self, _capture_exception=False):
self._assert_active(prepared_ok=True, rollback_ok=True)
stx = self.session.transaction
if stx is not self:
for subtransaction in stx._iterate_parents(upto=self):
subtransaction.close()
if self._state in (ACTIVE, PREPARED):
for transaction in self._iterate_parents():
if transaction._parent is None or transaction.nested:
transaction._rollback_impl()
transaction._state = DEACTIVE
break
else:
transaction._state = DEACTIVE
sess = self.session
if self.session._enable_transaction_accounting and \
not sess._is_clean():
# if items were added, deleted, or mutated
# here, we need to re-restore the snapshot
util.warn(
"Session's state has been changed on "
"a non-active transaction - this state "
"will be discarded.")
self._restore_snapshot(dirty_only=self.nested)
self.close()
if self._parent and _capture_exception:
self._parent._rollback_exception = sys.exc_info()[1]
sess.dispatch.after_soft_rollback(sess, self)
return self._parent
def _rollback_impl(self):
for t in set(self._connections.values()):
t[1].rollback()
if self.session._enable_transaction_accounting:
self._restore_snapshot(dirty_only=self.nested)
self.session.dispatch.after_rollback(self.session)
def close(self):
self.session.transaction = self._parent
if self._parent is None:
for connection, transaction, autoclose in \
set(self._connections.values()):
if autoclose:
connection.close()
else:
transaction.close()
self._state = CLOSED
if self.session.dispatch.after_transaction_end:
self.session.dispatch.after_transaction_end(self.session, self)
if self._parent is None:
if not self.session.autocommit:
self.session.begin()
self.session = None
self._connections = None
def __enter__(self):
return self
def __exit__(self, type, value, traceback):
self._assert_active(deactive_ok=True, prepared_ok=True)
if self.session.transaction is None:
return
if type is None:
try:
self.commit()
except:
with util.safe_reraise():
self.rollback()
else:
self.rollback()
class Session(_SessionClassMethods):
"""Manages persistence operations for ORM-mapped objects.
The Session's usage paradigm is described at :doc:`/orm/session`.
"""
public_methods = (
'__contains__', '__iter__', 'add', 'add_all', 'begin', 'begin_nested',
'close', 'commit', 'connection', 'delete', 'execute', 'expire',
'expire_all', 'expunge', 'expunge_all', 'flush', 'get_bind',
'is_modified',
'merge', 'query', 'refresh', 'rollback',
'scalar')
def __init__(self, bind=None, autoflush=True, expire_on_commit=True,
_enable_transaction_accounting=True,
autocommit=False, twophase=False,
weak_identity_map=True, binds=None, extension=None,
query_cls=query.Query):
"""Construct a new Session.
See also the :class:`.sessionmaker` function which is used to
generate a :class:`.Session`-producing callable with a given
set of arguments.
:param autocommit:
.. warning::
The autocommit flag is **not for general use**, and if it is used,
queries should only be invoked within the span of a
:meth:`.Session.begin` / :meth:`.Session.commit` pair. Executing
queries outside of a demarcated transaction is a legacy mode
of usage, and can in some cases lead to concurrent connection
checkouts.
Defaults to ``False``. When ``True``, the
:class:`.Session` does not keep a persistent transaction running, and
will acquire connections from the engine on an as-needed basis,
returning them immediately after their use. Flushes will begin and
commit (or possibly rollback) their own transaction if no
transaction is present. When using this mode, the
:meth:`.Session.begin` method is used to explicitly start
transactions.
.. seealso::
:ref:`session_autocommit`
:param autoflush: When ``True``, all query operations will issue a
``flush()`` call to this ``Session`` before proceeding. This is a
convenience feature so that ``flush()`` need not be called
repeatedly in order for database queries to retrieve results. It's
typical that ``autoflush`` is used in conjunction with
``autocommit=False``. In this scenario, explicit calls to
``flush()`` are rarely needed; you usually only need to call
``commit()`` (which flushes) to finalize changes.
:param bind: An optional ``Engine`` or ``Connection`` to which this
``Session`` should be bound. When specified, all SQL operations
performed by this session will execute via this connectable.
:param binds: An optional dictionary which contains more granular
"bind" information than the ``bind`` parameter provides. This
dictionary can map individual ``Table`` instances as well as
``Mapper`` instances to individual ``Engine`` or ``Connection``
objects. Operations which proceed relative to a particular
``Mapper`` will consult this dictionary for the direct ``Mapper``
instance as well as the mapper's ``mapped_table`` attribute in
order to locate an connectable to use. The full resolution is
described in the ``get_bind()`` method of ``Session``.
Usage looks like::
Session = sessionmaker(binds={
SomeMappedClass: create_engine('postgresql://engine1'),
somemapper: create_engine('postgresql://engine2'),
some_table: create_engine('postgresql://engine3'),
})
Also see the :meth:`.Session.bind_mapper`
and :meth:`.Session.bind_table` methods.
:param \class_: Specify an alternate class other than
``sqlalchemy.orm.session.Session`` which should be used by the
returned class. This is the only argument that is local to the
``sessionmaker()`` function, and is not sent directly to the
constructor for ``Session``.
:param _enable_transaction_accounting: Defaults to ``True``. A
legacy-only flag which when ``False`` disables *all* 0.5-style
object accounting on transaction boundaries, including auto-expiry
of instances on rollback and commit, maintenance of the "new" and
"deleted" lists upon rollback, and autoflush of pending changes upon
begin(), all of which are interdependent.
:param expire_on_commit: Defaults to ``True``. When ``True``, all
instances will be fully expired after each ``commit()``, so that
all attribute/object access subsequent to a completed transaction
will load from the most recent database state.
:param extension: An optional
:class:`~.SessionExtension` instance, or a list
of such instances, which will receive pre- and post- commit and
flush events, as well as a post-rollback event. **Deprecated.**
Please see :class:`.SessionEvents`.
:param query_cls: Class which should be used to create new Query
objects, as returned by the ``query()`` method. Defaults to
:class:`~sqlalchemy.orm.query.Query`.
:param twophase: When ``True``, all transactions will be started as
a "two phase" transaction, i.e. using the "two phase" semantics
of the database in use along with an XID. During a ``commit()``,
after ``flush()`` has been issued for all attached databases, the
``prepare()`` method on each database's ``TwoPhaseTransaction``
will be called. This allows each database to roll back the entire
transaction, before each transaction is committed.
:param weak_identity_map: Defaults to ``True`` - when set to
``False``, objects placed in the :class:`.Session` will be
strongly referenced until explicitly removed or the
:class:`.Session` is closed. **Deprecated** - this option
is obsolete.
"""
if weak_identity_map:
self._identity_cls = identity.WeakInstanceDict
else:
util.warn_deprecated("weak_identity_map=False is deprecated. "
"This feature is not needed.")
self._identity_cls = identity.StrongInstanceDict
self.identity_map = self._identity_cls()
self._new = {} # InstanceState->object, strong refs object
self._deleted = {} # same
self.bind = bind
self.__binds = {}
self._flushing = False
self._warn_on_events = False
self.transaction = None
self.hash_key = _new_sessionid()
self.autoflush = autoflush
self.autocommit = autocommit
self.expire_on_commit = expire_on_commit
self._enable_transaction_accounting = _enable_transaction_accounting
self.twophase = twophase
self._query_cls = query_cls
if extension:
for ext in util.to_list(extension):
SessionExtension._adapt_listener(self, ext)
if binds is not None:
for mapperortable, bind in binds.iteritems():
if isinstance(mapperortable, (type, Mapper)):
self.bind_mapper(mapperortable, bind)
else:
self.bind_table(mapperortable, bind)
if not self.autocommit:
self.begin()
_sessions[self.hash_key] = self
dispatch = event.dispatcher(SessionEvents)
connection_callable = None
transaction = None
"""The current active or inactive :class:`.SessionTransaction`."""
def begin(self, subtransactions=False, nested=False):
"""Begin a transaction on this Session.
If this Session is already within a transaction, either a plain
transaction or nested transaction, an error is raised, unless
``subtransactions=True`` or ``nested=True`` is specified.
The ``subtransactions=True`` flag indicates that this
:meth:`~.Session.begin` can create a subtransaction if a transaction
is already in progress. For documentation on subtransactions, please
see :ref:`session_subtransactions`.
The ``nested`` flag begins a SAVEPOINT transaction and is equivalent
to calling :meth:`~.Session.begin_nested`. For documentation on
SAVEPOINT transactions, please see :ref:`session_begin_nested`.
"""
if self.transaction is not None:
if subtransactions or nested:
self.transaction = self.transaction._begin(
nested=nested)
else:
raise sa_exc.InvalidRequestError(
"A transaction is already begun. Use "
"subtransactions=True to allow subtransactions.")
else:
self.transaction = SessionTransaction(
self, nested=nested)
return self.transaction # needed for __enter__/__exit__ hook
def begin_nested(self):
"""Begin a `nested` transaction on this Session.
The target database(s) must support SQL SAVEPOINTs or a
SQLAlchemy-supported vendor implementation of the idea.
For documentation on SAVEPOINT
transactions, please see :ref:`session_begin_nested`.
"""
return self.begin(nested=True)
def rollback(self):
"""Rollback the current transaction in progress.
If no transaction is in progress, this method is a pass-through.
This method rolls back the current transaction or nested transaction
regardless of subtransactions being in effect. All subtransactions up
to the first real transaction are closed. Subtransactions occur when
begin() is called multiple times.
.. seealso::
:ref:`session_rollback`
"""
if self.transaction is None:
pass
else:
self.transaction.rollback()
def commit(self):
"""Flush pending changes and commit the current transaction.
If no transaction is in progress, this method raises an
:exc:`~sqlalchemy.exc.InvalidRequestError`.
By default, the :class:`.Session` also expires all database
loaded state on all ORM-managed attributes after transaction commit.
This so that subsequent operations load the most recent
data from the database. This behavior can be disabled using
the ``expire_on_commit=False`` option to :class:`.sessionmaker` or
the :class:`.Session` constructor.
If a subtransaction is in effect (which occurs when begin() is called
multiple times), the subtransaction will be closed, and the next call
to ``commit()`` will operate on the enclosing transaction.
When using the :class:`.Session` in its default mode of
``autocommit=False``, a new transaction will
be begun immediately after the commit, but note that the newly begun
transaction does *not* use any connection resources until the first
SQL is actually emitted.
.. seealso::
:ref:`session_committing`
"""
if self.transaction is None:
if not self.autocommit:
self.begin()
else:
raise sa_exc.InvalidRequestError("No transaction is begun.")
self.transaction.commit()
def prepare(self):
"""Prepare the current transaction in progress for two phase commit.
If no transaction is in progress, this method raises an
:exc:`~sqlalchemy.exc.InvalidRequestError`.
Only root transactions of two phase sessions can be prepared. If the
current transaction is not such, an
:exc:`~sqlalchemy.exc.InvalidRequestError` is raised.
"""
if self.transaction is None:
if not self.autocommit:
self.begin()
else:
raise sa_exc.InvalidRequestError("No transaction is begun.")
self.transaction.prepare()
def connection(self, mapper=None, clause=None,
bind=None,
close_with_result=False,
**kw):
"""Return a :class:`.Connection` object corresponding to this
:class:`.Session` object's transactional state.
If this :class:`.Session` is configured with ``autocommit=False``,
either the :class:`.Connection` corresponding to the current
transaction is returned, or if no transaction is in progress, a new
one is begun and the :class:`.Connection` returned (note that no
transactional state is established with the DBAPI until the first
SQL statement is emitted).
Alternatively, if this :class:`.Session` is configured with
``autocommit=True``, an ad-hoc :class:`.Connection` is returned
using :meth:`.Engine.contextual_connect` on the underlying
:class:`.Engine`.
Ambiguity in multi-bind or unbound :class:`.Session` objects can be
resolved through any of the optional keyword arguments. This
ultimately makes usage of the :meth:`.get_bind` method for resolution.
:param bind:
Optional :class:`.Engine` to be used as the bind. If
this engine is already involved in an ongoing transaction,
that connection will be used. This argument takes precedence
over ``mapper``, ``clause``.
:param mapper:
Optional :func:`.mapper` mapped class, used to identify
the appropriate bind. This argument takes precedence over
``clause``.
:param clause:
A :class:`.ClauseElement` (i.e. :func:`~.sql.expression.select`,
:func:`~.sql.expression.text`,
etc.) which will be used to locate a bind, if a bind
cannot otherwise be identified.
:param close_with_result: Passed to :meth:`Engine.connect`, indicating
the :class:`.Connection` should be considered "single use",
automatically closing when the first result set is closed. This
flag only has an effect if this :class:`.Session` is configured with
``autocommit=True`` and does not already have a transaction
in progress.
:param \**kw:
Additional keyword arguments are sent to :meth:`get_bind()`,
allowing additional arguments to be passed to custom
implementations of :meth:`get_bind`.
"""
if bind is None:
bind = self.get_bind(mapper, clause=clause, **kw)
return self._connection_for_bind(bind,
close_with_result=close_with_result)
def _connection_for_bind(self, engine, **kwargs):
if self.transaction is not None:
return self.transaction._connection_for_bind(engine)
else:
return engine.contextual_connect(**kwargs)
def execute(self, clause, params=None, mapper=None, bind=None, **kw):
"""Execute a SQL expression construct or string statement within
the current transaction.
Returns a :class:`.ResultProxy` representing
results of the statement execution, in the same manner as that of an
:class:`.Engine` or
:class:`.Connection`.
E.g.::
result = session.execute(
user_table.select().where(user_table.c.id == 5)
)
:meth:`~.Session.execute` accepts any executable clause construct, such
as :func:`~.sql.expression.select`,
:func:`~.sql.expression.insert`,
:func:`~.sql.expression.update`,
:func:`~.sql.expression.delete`, and
:func:`~.sql.expression.text`. Plain SQL strings can be passed
as well, which in the case of :meth:`.Session.execute` only
will be interpreted the same as if it were passed via a
:func:`~.expression.text` construct. That is, the following usage::
result = session.execute(
"SELECT * FROM user WHERE id=:param",
{"param":5}
)
is equivalent to::
from sqlalchemy import text
result = session.execute(
text("SELECT * FROM user WHERE id=:param"),
{"param":5}
)
The second positional argument to :meth:`.Session.execute` is an
optional parameter set. Similar to that of
:meth:`.Connection.execute`, whether this is passed as a single
dictionary, or a list of dictionaries, determines whether the DBAPI
cursor's ``execute()`` or ``executemany()`` is used to execute the
statement. An INSERT construct may be invoked for a single row::
result = session.execute(users.insert(), {"id": 7, "name": "somename"})
or for multiple rows::
result = session.execute(users.insert(), [
{"id": 7, "name": "somename7"},
{"id": 8, "name": "somename8"},
{"id": 9, "name": "somename9"}
])
The statement is executed within the current transactional context of
this :class:`.Session`. The :class:`.Connection` which is used
to execute the statement can also be acquired directly by
calling the :meth:`.Session.connection` method. Both methods use
a rule-based resolution scheme in order to determine the
:class:`.Connection`, which in the average case is derived directly
from the "bind" of the :class:`.Session` itself, and in other cases
can be based on the :func:`.mapper`
and :class:`.Table` objects passed to the method; see the documentation
for :meth:`.Session.get_bind` for a full description of this scheme.
The :meth:`.Session.execute` method does *not* invoke autoflush.
The :class:`.ResultProxy` returned by the :meth:`.Session.execute`
method is returned with the "close_with_result" flag set to true;
the significance of this flag is that if this :class:`.Session` is
autocommitting and does not have a transaction-dedicated
:class:`.Connection` available, a temporary :class:`.Connection` is
established for the statement execution, which is closed (meaning,
returned to the connection pool) when the :class:`.ResultProxy` has
consumed all available data. This applies *only* when the
:class:`.Session` is configured with autocommit=True and no
transaction has been started.
:param clause:
An executable statement (i.e. an :class:`.Executable` expression
such as :func:`.expression.select`) or string SQL statement
to be executed.
:param params:
Optional dictionary, or list of dictionaries, containing
bound parameter values. If a single dictionary, single-row
execution occurs; if a list of dictionaries, an
"executemany" will be invoked. The keys in each dictionary
must correspond to parameter names present in the statement.
:param mapper:
Optional :func:`.mapper` or mapped class, used to identify
the appropriate bind. This argument takes precedence over
``clause`` when locating a bind. See :meth:`.Session.get_bind`
for more details.
:param bind:
Optional :class:`.Engine` to be used as the bind. If
this engine is already involved in an ongoing transaction,
that connection will be used. This argument takes
precedence over ``mapper`` and ``clause`` when locating
a bind.
:param \**kw:
Additional keyword arguments are sent to :meth:`.Session.get_bind()`
to allow extensibility of "bind" schemes.
.. seealso::
:ref:`sqlexpression_toplevel` - Tutorial on using Core SQL
constructs.
:ref:`connections_toplevel` - Further information on direct
statement execution.
:meth:`.Connection.execute` - core level statement execution
method, which is :meth:`.Session.execute` ultimately uses
in order to execute the statement.
"""
clause = expression._literal_as_text(clause)
if bind is None:
bind = self.get_bind(mapper, clause=clause, **kw)
return self._connection_for_bind(bind, close_with_result=True).execute(
clause, params or {})
def scalar(self, clause, params=None, mapper=None, bind=None, **kw):
"""Like :meth:`~.Session.execute` but return a scalar result."""
return self.execute(
clause, params=params, mapper=mapper, bind=bind, **kw).scalar()
def close(self):
"""Close this Session.
This clears all items and ends any transaction in progress.
If this session were created with ``autocommit=False``, a new
transaction is immediately begun. Note that this new transaction does
not use any connection resources until they are first needed.
"""
self.expunge_all()
if self.transaction is not None:
for transaction in self.transaction._iterate_parents():
transaction.close()
def expunge_all(self):
"""Remove all object instances from this ``Session``.
This is equivalent to calling ``expunge(obj)`` on all objects in this
``Session``.
"""
for state in self.identity_map.all_states() + list(self._new):
state._detach()
self.identity_map = self._identity_cls()
self._new = {}
self._deleted = {}
# TODO: need much more test coverage for bind_mapper() and similar !
# TODO: + crystalize + document resolution order
# vis. bind_mapper/bind_table
def bind_mapper(self, mapper, bind):
"""Bind operations for a mapper to a Connectable.
mapper
A mapper instance or mapped class
bind
Any Connectable: a ``Engine`` or ``Connection``.
All subsequent operations involving this mapper will use the given
`bind`.
"""
if isinstance(mapper, type):
mapper = class_mapper(mapper)
self.__binds[mapper.base_mapper] = bind
for t in mapper._all_tables:
self.__binds[t] = bind
def bind_table(self, table, bind):
"""Bind operations on a Table to a Connectable.
table
A ``Table`` instance
bind
Any Connectable: a ``Engine`` or ``Connection``.
All subsequent operations involving this ``Table`` will use the
given `bind`.
"""
self.__binds[table] = bind
def get_bind(self, mapper=None, clause=None):
"""Return a "bind" to which this :class:`.Session` is bound.
The "bind" is usually an instance of :class:`.Engine`,
except in the case where the :class:`.Session` has been
explicitly bound directly to a :class:`.Connection`.
For a multiply-bound or unbound :class:`.Session`, the
``mapper`` or ``clause`` arguments are used to determine the
appropriate bind to return.
Note that the "mapper" argument is usually present
when :meth:`.Session.get_bind` is called via an ORM
operation such as a :meth:`.Session.query`, each
individual INSERT/UPDATE/DELETE operation within a
:meth:`.Session.flush`, call, etc.
The order of resolution is:
1. if mapper given and session.binds is present,
locate a bind based on mapper.
2. if clause given and session.binds is present,
locate a bind based on :class:`.Table` objects
found in the given clause present in session.binds.
3. if session.bind is present, return that.
4. if clause given, attempt to return a bind
linked to the :class:`.MetaData` ultimately
associated with the clause.
5. if mapper given, attempt to return a bind
linked to the :class:`.MetaData` ultimately
associated with the :class:`.Table` or other
selectable to which the mapper is mapped.
6. No bind can be found, :exc:`~sqlalchemy.exc.UnboundExecutionError`
is raised.
:param mapper:
Optional :func:`.mapper` mapped class or instance of
:class:`.Mapper`. The bind can be derived from a :class:`.Mapper`
first by consulting the "binds" map associated with this
:class:`.Session`, and secondly by consulting the :class:`.MetaData`
associated with the :class:`.Table` to which the :class:`.Mapper`
is mapped for a bind.
:param clause:
A :class:`.ClauseElement` (i.e. :func:`~.sql.expression.select`,
:func:`~.sql.expression.text`,
etc.). If the ``mapper`` argument is not present or could not
produce a bind, the given expression construct will be searched
for a bound element, typically a :class:`.Table` associated with
bound :class:`.MetaData`.
"""
if mapper is clause is None:
if self.bind:
return self.bind
else:
raise sa_exc.UnboundExecutionError(
"This session is not bound to a single Engine or "
"Connection, and no context was provided to locate "
"a binding.")
c_mapper = mapper is not None and _class_to_mapper(mapper) or None
# manually bound?
if self.__binds:
if c_mapper:
if c_mapper.base_mapper in self.__binds:
return self.__binds[c_mapper.base_mapper]
elif c_mapper.mapped_table in self.__binds:
return self.__binds[c_mapper.mapped_table]
if clause is not None:
for t in sql_util.find_tables(clause, include_crud=True):
if t in self.__binds:
return self.__binds[t]
if self.bind:
return self.bind
if isinstance(clause, sql.expression.ClauseElement) and clause.bind:
return clause.bind
if c_mapper and c_mapper.mapped_table.bind:
return c_mapper.mapped_table.bind
context = []
if mapper is not None:
context.append('mapper %s' % c_mapper)
if clause is not None:
context.append('SQL expression')
raise sa_exc.UnboundExecutionError(
"Could not locate a bind configured on %s or this Session" % (
', '.join(context)))
def query(self, *entities, **kwargs):
"""Return a new ``Query`` object corresponding to this ``Session``."""
return self._query_cls(entities, self, **kwargs)
@property
@util.contextmanager
def no_autoflush(self):
"""Return a context manager that disables autoflush.
e.g.::
with session.no_autoflush:
some_object = SomeClass()
session.add(some_object)
# won't autoflush
some_object.related_thing = session.query(SomeRelated).first()
Operations that proceed within the ``with:`` block
will not be subject to flushes occurring upon query
access. This is useful when initializing a series
of objects which involve existing database queries,
where the uncompleted object should not yet be flushed.
.. versionadded:: 0.7.6
"""
autoflush = self.autoflush
self.autoflush = False
yield self
self.autoflush = autoflush
def _autoflush(self):
if self.autoflush and not self._flushing:
self.flush()
def refresh(self, instance, attribute_names=None, lockmode=None):
"""Expire and refresh the attributes on the given instance.
A query will be issued to the database and all attributes will be
refreshed with their current database value.
Lazy-loaded relational attributes will remain lazily loaded, so that
the instance-wide refresh operation will be followed immediately by
the lazy load of that attribute.
Eagerly-loaded relational attributes will eagerly load within the
single refresh operation.
Note that a highly isolated transaction will return the same values as
were previously read in that same transaction, regardless of changes
in database state outside of that transaction - usage of
:meth:`~Session.refresh` usually only makes sense if non-ORM SQL
statement were emitted in the ongoing transaction, or if autocommit
mode is turned on.
:param attribute_names: optional. An iterable collection of
string attribute names indicating a subset of attributes to
be refreshed.
:param lockmode: Passed to the :class:`~sqlalchemy.orm.query.Query`
as used by :meth:`~sqlalchemy.orm.query.Query.with_lockmode`.
"""
try:
state = attributes.instance_state(instance)
except exc.NO_STATE:
raise exc.UnmappedInstanceError(instance)
self._expire_state(state, attribute_names)
if loading.load_on_ident(
self.query(object_mapper(instance)),
state.key, refresh_state=state,
lockmode=lockmode,
only_load_props=attribute_names) is None:
raise sa_exc.InvalidRequestError(
"Could not refresh instance '%s'" %
orm_util.instance_str(instance))
def expire_all(self):
"""Expires all persistent instances within this Session.
When any attributes on a persistent instance is next accessed,
a query will be issued using the
:class:`.Session` object's current transactional context in order to
load all expired attributes for the given instance. Note that
a highly isolated transaction will return the same values as were
previously read in that same transaction, regardless of changes
in database state outside of that transaction.
To expire individual objects and individual attributes
on those objects, use :meth:`Session.expire`.
The :class:`.Session` object's default behavior is to
expire all state whenever the :meth:`Session.rollback`
or :meth:`Session.commit` methods are called, so that new
state can be loaded for the new transaction. For this reason,
calling :meth:`Session.expire_all` should not be needed when
autocommit is ``False``, assuming the transaction is isolated.
"""
for state in self.identity_map.all_states():
state._expire(state.dict, self.identity_map._modified)
def expire(self, instance, attribute_names=None):
"""Expire the attributes on an instance.
Marks the attributes of an instance as out of date. When an expired
attribute is next accessed, a query will be issued to the
:class:`.Session` object's current transactional context in order to
load all expired attributes for the given instance. Note that
a highly isolated transaction will return the same values as were
previously read in that same transaction, regardless of changes
in database state outside of that transaction.
To expire all objects in the :class:`.Session` simultaneously,
use :meth:`Session.expire_all`.
The :class:`.Session` object's default behavior is to
expire all state whenever the :meth:`Session.rollback`
or :meth:`Session.commit` methods are called, so that new
state can be loaded for the new transaction. For this reason,
calling :meth:`Session.expire` only makes sense for the specific
case that a non-ORM SQL statement was emitted in the current
transaction.
:param instance: The instance to be refreshed.
:param attribute_names: optional list of string attribute names
indicating a subset of attributes to be expired.
"""
try:
state = attributes.instance_state(instance)
except exc.NO_STATE:
raise exc.UnmappedInstanceError(instance)
self._expire_state(state, attribute_names)
def _expire_state(self, state, attribute_names):
self._validate_persistent(state)
if attribute_names:
state._expire_attributes(state.dict, attribute_names)
else:
# pre-fetch the full cascade since the expire is going to
# remove associations
cascaded = list(state.manager.mapper.cascade_iterator(
'refresh-expire', state))
self._conditional_expire(state)
for o, m, st_, dct_ in cascaded:
self._conditional_expire(st_)
def _conditional_expire(self, state):
"""Expire a state if persistent, else expunge if pending"""
if state.key:
state._expire(state.dict, self.identity_map._modified)
elif state in self._new:
self._new.pop(state)
state._detach()
@util.deprecated("0.7", "The non-weak-referencing identity map "
"feature is no longer needed.")
def prune(self):
"""Remove unreferenced instances cached in the identity map.
Note that this method is only meaningful if "weak_identity_map" is set
to False. The default weak identity map is self-pruning.
Removes any object in this Session's identity map that is not
referenced in user code, modified, new or scheduled for deletion.
Returns the number of objects pruned.
"""
return self.identity_map.prune()
def expunge(self, instance):
"""Remove the `instance` from this ``Session``.
This will free all internal references to the instance. Cascading
will be applied according to the *expunge* cascade rule.
"""
try:
state = attributes.instance_state(instance)
except exc.NO_STATE:
raise exc.UnmappedInstanceError(instance)
if state.session_id is not self.hash_key:
raise sa_exc.InvalidRequestError(
"Instance %s is not present in this Session" %
orm_util.state_str(state))
cascaded = list(state.manager.mapper.cascade_iterator(
'expunge', state))
self._expunge_state(state)
for o, m, st_, dct_ in cascaded:
self._expunge_state(st_)
def _expunge_state(self, state):
if state in self._new:
self._new.pop(state)
state._detach()
elif self.identity_map.contains_state(state):
self.identity_map.discard(state)
self._deleted.pop(state, None)
state._detach()
elif self.transaction:
self.transaction._deleted.pop(state, None)
def _register_newly_persistent(self, states):
for state in states:
mapper = _state_mapper(state)
# prevent against last minute dereferences of the object
obj = state.obj()
if obj is not None:
instance_key = mapper._identity_key_from_state(state)
if _none_set.issubset(instance_key[1]) and \
not mapper.allow_partial_pks or \
_none_set.issuperset(instance_key[1]):
raise exc.FlushError(
"Instance %s has a NULL identity key. If this is an "
"auto-generated value, check that the database table "
"allows generation of new primary key values, and "
"that the mapped Column object is configured to "
"expect these generated values. Ensure also that "
"this flush() is not occurring at an inappropriate "
"time, such aswithin a load() event."
% orm_util.state_str(state)
)
if state.key is None:
state.key = instance_key
elif state.key != instance_key:
# primary key switch. use discard() in case another
# state has already replaced this one in the identity
# map (see test/orm/test_naturalpks.py ReversePKsTest)
self.identity_map.discard(state)
if state in self.transaction._key_switches:
orig_key = self.transaction._key_switches[state][0]
else:
orig_key = state.key
self.transaction._key_switches[state] = (
orig_key, instance_key)
state.key = instance_key
self.identity_map.replace(state)
statelib.InstanceState._commit_all_states(
((state, state.dict) for state in states),
self.identity_map
)
self._register_altered(states)
# remove from new last, might be the last strong ref
for state in set(states).intersection(self._new):
self._new.pop(state)
def _register_altered(self, states):
if self._enable_transaction_accounting and self.transaction:
for state in states:
if state in self._new:
self.transaction._new[state] = True
else:
self.transaction._dirty[state] = True
def _remove_newly_deleted(self, states):
for state in states:
if self._enable_transaction_accounting and self.transaction:
self.transaction._deleted[state] = True
self.identity_map.discard(state)
self._deleted.pop(state, None)
state.deleted = True
def add(self, instance, _warn=True):
"""Place an object in the ``Session``.
Its state will be persisted to the database on the next flush
operation.
Repeated calls to ``add()`` will be ignored. The opposite of ``add()``
is ``expunge()``.
"""
if _warn and self._warn_on_events:
self._flush_warning("Session.add()")
try:
state = attributes.instance_state(instance)
except exc.NO_STATE:
raise exc.UnmappedInstanceError(instance)
self._save_or_update_state(state)
def add_all(self, instances):
"""Add the given collection of instances to this ``Session``."""
if self._warn_on_events:
self._flush_warning("Session.add_all()")
for instance in instances:
self.add(instance, _warn=False)
def _save_or_update_state(self, state):
self._save_or_update_impl(state)
mapper = _state_mapper(state)
for o, m, st_, dct_ in mapper.cascade_iterator(
'save-update',
state,
halt_on=self._contains_state):
self._save_or_update_impl(st_)
def delete(self, instance):
"""Mark an instance as deleted.
The database delete operation occurs upon ``flush()``.
"""
if self._warn_on_events:
self._flush_warning("Session.delete()")
try:
state = attributes.instance_state(instance)
except exc.NO_STATE:
raise exc.UnmappedInstanceError(instance)
if state.key is None:
raise sa_exc.InvalidRequestError(
"Instance '%s' is not persisted" %
orm_util.state_str(state))
if state in self._deleted:
return
# ensure object is attached to allow the
# cascade operation to load deferred attributes
# and collections
self._attach(state, include_before=True)
# grab the cascades before adding the item to the deleted list
# so that autoflush does not delete the item
# the strong reference to the instance itself is significant here
cascade_states = list(state.manager.mapper.cascade_iterator(
'delete', state))
self._deleted[state] = state.obj()
self.identity_map.add(state)
for o, m, st_, dct_ in cascade_states:
self._delete_impl(st_)
def merge(self, instance, load=True):
"""Copy the state of a given instance into a corresponding instance
within this :class:`.Session`.
:meth:`.Session.merge` examines the primary key attributes of the
source instance, and attempts to reconcile it with an instance of the
same primary key in the session. If not found locally, it attempts
to load the object from the database based on primary key, and if
none can be located, creates a new instance. The state of each
attribute on the source instance is then copied to the target instance.
The resulting target instance is then returned by the method; the
original source instance is left unmodified, and un-associated with the
:class:`.Session` if not already.
This operation cascades to associated instances if the association is
mapped with ``cascade="merge"``.
See :ref:`unitofwork_merging` for a detailed discussion of merging.
:param instance: Instance to be merged.
:param load: Boolean, when False, :meth:`.merge` switches into
a "high performance" mode which causes it to forego emitting history
events as well as all database access. This flag is used for
cases such as transferring graphs of objects into a :class:`.Session`
from a second level cache, or to transfer just-loaded objects
into the :class:`.Session` owned by a worker thread or process
without re-querying the database.
The ``load=False`` use case adds the caveat that the given
object has to be in a "clean" state, that is, has no pending changes
to be flushed - even if the incoming object is detached from any
:class:`.Session`. This is so that when
the merge operation populates local attributes and
cascades to related objects and
collections, the values can be "stamped" onto the
target object as is, without generating any history or attribute
events, and without the need to reconcile the incoming data with
any existing related objects or collections that might not
be loaded. The resulting objects from ``load=False`` are always
produced as "clean", so it is only appropriate that the given objects
should be "clean" as well, else this suggests a mis-use of the method.
"""
if self._warn_on_events:
self._flush_warning("Session.merge()")
_recursive = {}
if load:
# flush current contents if we expect to load data
self._autoflush()
object_mapper(instance) # verify mapped
autoflush = self.autoflush
try:
self.autoflush = False
return self._merge(
attributes.instance_state(instance),
attributes.instance_dict(instance),
load=load, _recursive=_recursive)
finally:
self.autoflush = autoflush
def _merge(self, state, state_dict, load=True, _recursive=None):
mapper = _state_mapper(state)
if state in _recursive:
return _recursive[state]
new_instance = False
key = state.key
if key is None:
if not load:
raise sa_exc.InvalidRequestError(
"merge() with load=False option does not support "
"objects transient (i.e. unpersisted) objects. flush() "
"all changes on mapped instances before merging with "
"load=False.")
key = mapper._identity_key_from_state(state)
if key in self.identity_map:
merged = self.identity_map[key]
elif not load:
if state.modified:
raise sa_exc.InvalidRequestError(
"merge() with load=False option does not support "
"objects marked as 'dirty'. flush() all changes on "
"mapped instances before merging with load=False.")
merged = mapper.class_manager.new_instance()
merged_state = attributes.instance_state(merged)
merged_state.key = key
self._update_impl(merged_state)
new_instance = True
elif not _none_set.issubset(key[1]) or \
(mapper.allow_partial_pks and
not _none_set.issuperset(key[1])):
merged = self.query(mapper.class_).get(key[1])
else:
merged = None
if merged is None:
merged = mapper.class_manager.new_instance()
merged_state = attributes.instance_state(merged)
merged_dict = attributes.instance_dict(merged)
new_instance = True
self._save_or_update_state(merged_state)
else:
merged_state = attributes.instance_state(merged)
merged_dict = attributes.instance_dict(merged)
_recursive[state] = merged
# check that we didn't just pull the exact same
# state out.
if state is not merged_state:
# version check if applicable
if mapper.version_id_col is not None:
existing_version = mapper._get_state_attr_by_column(
state,
state_dict,
mapper.version_id_col,
passive=attributes.PASSIVE_NO_INITIALIZE)
merged_version = mapper._get_state_attr_by_column(
merged_state,
merged_dict,
mapper.version_id_col,
passive=attributes.PASSIVE_NO_INITIALIZE)
if existing_version is not attributes.PASSIVE_NO_RESULT and \
merged_version is not attributes.PASSIVE_NO_RESULT and \
existing_version != merged_version:
raise exc.StaleDataError(
"Version id '%s' on merged state %s "
"does not match existing version '%s'. "
"Leave the version attribute unset when "
"merging to update the most recent version."
% (
existing_version,
orm_util.state_str(merged_state),
merged_version
))
merged_state.load_path = state.load_path
merged_state.load_options = state.load_options
for prop in mapper.iterate_properties:
prop.merge(self, state, state_dict,
merged_state, merged_dict,
load, _recursive)
if not load:
# remove any history
merged_state._commit_all(merged_dict, self.identity_map)
if new_instance:
merged_state.manager.dispatch.load(merged_state, None)
return merged
def _validate_persistent(self, state):
if not self.identity_map.contains_state(state):
raise sa_exc.InvalidRequestError(
"Instance '%s' is not persistent within this Session" %
orm_util.state_str(state))
def _save_impl(self, state):
if state.key is not None:
raise sa_exc.InvalidRequestError(
"Object '%s' already has an identity - it can't be registered "
"as pending" % orm_util.state_str(state))
self._before_attach(state)
if state not in self._new:
self._new[state] = state.obj()
state.insert_order = len(self._new)
self._attach(state)
def _update_impl(self, state, discard_existing=False):
if (self.identity_map.contains_state(state) and
state not in self._deleted):
return
if state.key is None:
raise sa_exc.InvalidRequestError(
"Instance '%s' is not persisted" %
orm_util.state_str(state))
if state.deleted:
raise sa_exc.InvalidRequestError(
"Instance '%s' has been deleted. Use the make_transient() "
"function to send this object back to the transient state." %
orm_util.state_str(state)
)
self._before_attach(state)
self._deleted.pop(state, None)
if discard_existing:
self.identity_map.replace(state)
else:
self.identity_map.add(state)
self._attach(state)
def _save_or_update_impl(self, state):
if state.key is None:
self._save_impl(state)
else:
self._update_impl(state)
def _delete_impl(self, state):
if state in self._deleted:
return
if state.key is None:
return
self._attach(state, include_before=True)
self._deleted[state] = state.obj()
self.identity_map.add(state)
def enable_relationship_loading(self, obj):
"""Associate an object with this :class:`.Session` for related
object loading.
.. warning::
:meth:`.enable_relationship_loading` exists to serve special
use cases and is not recommended for general use.
Accesses of attributes mapped with :func:`.relationship`
will attempt to load a value from the database using this
:class:`.Session` as the source of connectivity. The values
will be loaded based on foreign key values present on this
object - it follows that this functionality
generally only works for many-to-one-relationships.
The object will be attached to this session, but will
**not** participate in any persistence operations; its state
for almost all purposes will remain either "transient" or
"detached", except for the case of relationship loading.
Also note that backrefs will often not work as expected.
Altering a relationship-bound attribute on the target object
may not fire off a backref event, if the effective value
is what was already loaded from a foreign-key-holding value.
The :meth:`.Session.enable_relationship_loading` method supersedes
the ``load_on_pending`` flag on :func:`.relationship`. Unlike
that flag, :meth:`.Session.enable_relationship_loading` allows
an object to remain transient while still being able to load
related items.
To make a transient object associated with a :class:`.Session`
via :meth:`.Session.enable_relationship_loading` pending, add
it to the :class:`.Session` using :meth:`.Session.add` normally.
:meth:`.Session.enable_relationship_loading` does not improve
behavior when the ORM is used normally - object references should be
constructed at the object level, not at the foreign key level, so
that they are present in an ordinary way before flush()
proceeds. This method is not intended for general use.
.. versionadded:: 0.8
"""
state = attributes.instance_state(obj)
self._attach(state, include_before=True)
state._load_pending = True
def _before_attach(self, state):
if state.session_id != self.hash_key and \
self.dispatch.before_attach:
self.dispatch.before_attach(self, state.obj())
def _attach(self, state, include_before=False):
if state.key and \
state.key in self.identity_map and \
not self.identity_map.contains_state(state):
raise sa_exc.InvalidRequestError("Can't attach instance "
"%s; another instance with key %s is already "
"present in this session."
% (orm_util.state_str(state), state.key))
if state.session_id and \
state.session_id is not self.hash_key and \
state.session_id in _sessions:
raise sa_exc.InvalidRequestError(
"Object '%s' is already attached to session '%s' "
"(this is '%s')" % (orm_util.state_str(state),
state.session_id, self.hash_key))
if state.session_id != self.hash_key:
if include_before and \
self.dispatch.before_attach:
self.dispatch.before_attach(self, state.obj())
state.session_id = self.hash_key
if state.modified and state._strong_obj is None:
state._strong_obj = state.obj()
if self.dispatch.after_attach:
self.dispatch.after_attach(self, state.obj())
def __contains__(self, instance):
"""Return True if the instance is associated with this session.
The instance may be pending or persistent within the Session for a
result of True.
"""
try:
state = attributes.instance_state(instance)
except exc.NO_STATE:
raise exc.UnmappedInstanceError(instance)
return self._contains_state(state)
def __iter__(self):
"""Iterate over all pending or persistent instances within this
Session.
"""
return iter(list(self._new.values()) + self.identity_map.values())
def _contains_state(self, state):
return state in self._new or self.identity_map.contains_state(state)
def flush(self, objects=None):
"""Flush all the object changes to the database.
Writes out all pending object creations, deletions and modifications
to the database as INSERTs, DELETEs, UPDATEs, etc. Operations are
automatically ordered by the Session's unit of work dependency
solver.
Database operations will be issued in the current transactional
context and do not affect the state of the transaction, unless an
error occurs, in which case the entire transaction is rolled back.
You may flush() as often as you like within a transaction to move
changes from Python to the database's transaction buffer.
For ``autocommit`` Sessions with no active manual transaction, flush()
will create a transaction on the fly that surrounds the entire set of
operations int the flush.
:param objects: Optional; restricts the flush operation to operate
only on elements that are in the given collection.
This feature is for an extremely narrow set of use cases where
particular objects may need to be operated upon before the
full flush() occurs. It is not intended for general use.
"""
if self._flushing:
raise sa_exc.InvalidRequestError("Session is already flushing")
if self._is_clean():
return
try:
self._flushing = True
self._flush(objects)
finally:
self._flushing = False
def _flush_warning(self, method):
util.warn(
"Usage of the '%s' operation is not currently supported "
"within the execution stage of the flush process. "
"Results may not be consistent. Consider using alternative "
"event listeners or connection-level operations instead."
% method)
def _is_clean(self):
return not self.identity_map.check_modified() and \
not self._deleted and \
not self._new
def _flush(self, objects=None):
dirty = self._dirty_states
if not dirty and not self._deleted and not self._new:
self.identity_map._modified.clear()
return
flush_context = UOWTransaction(self)
if self.dispatch.before_flush:
self.dispatch.before_flush(self, flush_context, objects)
# re-establish "dirty states" in case the listeners
# added
dirty = self._dirty_states
deleted = set(self._deleted)
new = set(self._new)
dirty = set(dirty).difference(deleted)
# create the set of all objects we want to operate upon
if objects:
# specific list passed in
objset = set()
for o in objects:
try:
state = attributes.instance_state(o)
except exc.NO_STATE:
raise exc.UnmappedInstanceError(o)
objset.add(state)
else:
objset = None
# store objects whose fate has been decided
processed = set()
# put all saves/updates into the flush context. detect top-level
# orphans and throw them into deleted.
if objset:
proc = new.union(dirty).intersection(objset).difference(deleted)
else:
proc = new.union(dirty).difference(deleted)
for state in proc:
is_orphan = (
_state_mapper(state)._is_orphan(state) and state.has_identity)
flush_context.register_object(state, isdelete=is_orphan)
processed.add(state)
# put all remaining deletes into the flush context.
if objset:
proc = deleted.intersection(objset).difference(processed)
else:
proc = deleted.difference(processed)
for state in proc:
flush_context.register_object(state, isdelete=True)
if not flush_context.has_work:
return
flush_context.transaction = transaction = self.begin(
subtransactions=True)
try:
self._warn_on_events = True
try:
flush_context.execute()
finally:
self._warn_on_events = False
self.dispatch.after_flush(self, flush_context)
flush_context.finalize_flush_changes()
if not objects and self.identity_map._modified:
len_ = len(self.identity_map._modified)
statelib.InstanceState._commit_all_states(
[(state, state.dict) for state in
self.identity_map._modified],
instance_dict=self.identity_map)
util.warn("Attribute history events accumulated on %d "
"previously clean instances "
"within inner-flush event handlers have been reset, "
"and will not result in database updates. "
"Consider using set_committed_value() within "
"inner-flush event handlers to avoid this warning."
% len_)
# useful assertions:
#if not objects:
# assert not self.identity_map._modified
#else:
# assert self.identity_map._modified == \
# self.identity_map._modified.difference(objects)
self.dispatch.after_flush_postexec(self, flush_context)
transaction.commit()
except:
with util.safe_reraise():
transaction.rollback(_capture_exception=True)
def is_modified(self, instance, include_collections=True,
passive=True):
"""Return ``True`` if the given instance has locally
modified attributes.
This method retrieves the history for each instrumented
attribute on the instance and performs a comparison of the current
value to its previously committed value, if any.
It is in effect a more expensive and accurate
version of checking for the given instance in the
:attr:`.Session.dirty` collection; a full test for
each attribute's net "dirty" status is performed.
E.g.::
return session.is_modified(someobject)
.. versionchanged:: 0.8
When using SQLAlchemy 0.7 and earlier, the ``passive``
flag should **always** be explicitly set to ``True``,
else SQL loads/autoflushes may proceed which can affect
the modified state itself:
``session.is_modified(someobject, passive=True)``\ .
In 0.8 and above, the behavior is corrected and
this flag is ignored.
A few caveats to this method apply:
* Instances present in the :attr:`.Session.dirty` collection may report
``False`` when tested with this method. This is because
the object may have received change events via attribute
mutation, thus placing it in :attr:`.Session.dirty`,
but ultimately the state is the same as that loaded from
the database, resulting in no net change here.
* Scalar attributes may not have recorded the previously set
value when a new value was applied, if the attribute was not loaded,
or was expired, at the time the new value was received - in these
cases, the attribute is assumed to have a change, even if there is
ultimately no net change against its database value. SQLAlchemy in
most cases does not need the "old" value when a set event occurs, so
it skips the expense of a SQL call if the old value isn't present,
based on the assumption that an UPDATE of the scalar value is
usually needed, and in those few cases where it isn't, is less
expensive on average than issuing a defensive SELECT.
The "old" value is fetched unconditionally upon set only if the
attribute container has the ``active_history`` flag set to ``True``.
This flag is set typically for primary key attributes and scalar
object references that are not a simple many-to-one. To set this
flag for any arbitrary mapped column, use the ``active_history``
argument with :func:`.column_property`.
:param instance: mapped instance to be tested for pending changes.
:param include_collections: Indicates if multivalued collections
should be included in the operation. Setting this to ``False`` is a
way to detect only local-column based properties (i.e. scalar columns
or many-to-one foreign keys) that would result in an UPDATE for this
instance upon flush.
:param passive:
.. versionchanged:: 0.8
Ignored for backwards compatibility.
When using SQLAlchemy 0.7 and earlier, this flag should always
be set to ``True``.
"""
state = object_state(instance)
if not state.modified:
return False
dict_ = state.dict
for attr in state.manager.attributes:
if \
(
not include_collections and
hasattr(attr.impl, 'get_collection')
) or not hasattr(attr.impl, 'get_history'):
continue
(added, unchanged, deleted) = \
attr.impl.get_history(state, dict_,
passive=attributes.NO_CHANGE)
if added or deleted:
return True
else:
return False
@property
def is_active(self):
"""True if this :class:`.Session` is in "transaction mode" and
is not in "partial rollback" state.
The :class:`.Session` in its default mode of ``autocommit=False``
is essentially always in "transaction mode", in that a
:class:`.SessionTransaction` is associated with it as soon as
it is instantiated. This :class:`.SessionTransaction` is immediately
replaced with a new one as soon as it is ended, due to a rollback,
commit, or close operation.
"Transaction mode" does *not* indicate whether
or not actual database connection resources are in use; the
:class:`.SessionTransaction` object coordinates among zero or more
actual database transactions, and starts out with none, accumulating
individual DBAPI connections as different data sources are used
within its scope. The best way to track when a particular
:class:`.Session` has actually begun to use DBAPI resources is to
implement a listener using the :meth:`.SessionEvents.after_begin`
method, which will deliver both the :class:`.Session` as well as the
target :class:`.Connection` to a user-defined event listener.
The "partial rollback" state refers to when an "inner" transaction,
typically used during a flush, encounters an error and emits a
rollback of the DBAPI connection. At this point, the
:class:`.Session` is in "partial rollback" and awaits for the user to
call :meth:`.Session.rollback`, in order to close out the
transaction stack. It is in this "partial rollback" period that the
:attr:`.is_active` flag returns False. After the call to
:meth:`.Session.rollback`, the :class:`.SessionTransaction` is replaced
with a new one and :attr:`.is_active` returns ``True`` again.
When a :class:`.Session` is used in ``autocommit=True`` mode, the
:class:`.SessionTransaction` is only instantiated within the scope
of a flush call, or when :meth:`.Session.begin` is called. So
:attr:`.is_active` will always be ``False`` outside of a flush or
:meth:`.Session.begin` block in this mode, and will be ``True``
within the :meth:`.Session.begin` block as long as it doesn't enter
"partial rollback" state.
From all the above, it follows that the only purpose to this flag is
for application frameworks that wish to detect is a "rollback" is
necessary within a generic error handling routine, for
:class:`.Session` objects that would otherwise be in
"partial rollback" mode. In a typical integration case, this is also
not necessary as it is standard practice to emit
:meth:`.Session.rollback` unconditionally within the outermost
exception catch.
To track the transactional state of a :class:`.Session` fully,
use event listeners, primarily the :meth:`.SessionEvents.after_begin`,
:meth:`.SessionEvents.after_commit`,
:meth:`.SessionEvents.after_rollback` and related events.
"""
return self.transaction and self.transaction.is_active
identity_map = None
"""A mapping of object identities to objects themselves.
Iterating through ``Session.identity_map.values()`` provides
access to the full set of persistent objects (i.e., those
that have row identity) currently in the session.
.. seealso::
:func:`.identity_key` - helper function to produce the keys used
in this dictionary.
"""
@property
def _dirty_states(self):
"""The set of all persistent states considered dirty.
This method returns all states that were modified including
those that were possibly deleted.
"""
return self.identity_map._dirty_states()
@property
def dirty(self):
"""The set of all persistent instances considered dirty.
E.g.::
some_mapped_object in session.dirty
Instances are considered dirty when they were modified but not
deleted.
Note that this 'dirty' calculation is 'optimistic'; most
attribute-setting or collection modification operations will
mark an instance as 'dirty' and place it in this set, even if
there is no net change to the attribute's value. At flush
time, the value of each attribute is compared to its
previously saved value, and if there's no net change, no SQL
operation will occur (this is a more expensive operation so
it's only done at flush time).
To check if an instance has actionable net changes to its
attributes, use the :meth:`.Session.is_modified` method.
"""
return util.IdentitySet(
[state.obj()
for state in self._dirty_states
if state not in self._deleted])
@property
def deleted(self):
"The set of all instances marked as 'deleted' within this ``Session``"
return util.IdentitySet(self._deleted.values())
@property
def new(self):
"The set of all instances marked as 'new' within this ``Session``."
return util.IdentitySet(self._new.values())
class sessionmaker(_SessionClassMethods):
"""A configurable :class:`.Session` factory.
The :class:`.sessionmaker` factory generates new
:class:`.Session` objects when called, creating them given
the configurational arguments established here.
e.g.::
# global scope
Session = sessionmaker(autoflush=False)
# later, in a local scope, create and use a session:
sess = Session()
Any keyword arguments sent to the constructor itself will override the
"configured" keywords::
Session = sessionmaker()
# bind an individual session to a connection
sess = Session(bind=connection)
The class also includes a method :meth:`.configure`, which can
be used to specify additional keyword arguments to the factory, which
will take effect for subsequent :class:`.Session` objects generated.
This is usually used to associate one or more :class:`.Engine` objects
with an existing :class:`.sessionmaker` factory before it is first
used::
# application starts
Session = sessionmaker()
# ... later
engine = create_engine('sqlite:///foo.db')
Session.configure(bind=engine)
sess = Session()
.. seealso:
:ref:`session_getting` - introductory text on creating
sessions using :class:`.sessionmaker`.
"""
def __init__(self, bind=None, class_=Session, autoflush=True,
autocommit=False,
expire_on_commit=True, **kw):
"""Construct a new :class:`.sessionmaker`.
All arguments here except for ``class_`` correspond to arguments
accepted by :class:`.Session` directly. See the
:meth:`.Session.__init__` docstring for more details on parameters.
:param bind: a :class:`.Engine` or other :class:`.Connectable` with
which newly created :class:`.Session` objects will be associated.
:param class_: class to use in order to create new :class:`.Session`
objects. Defaults to :class:`.Session`.
:param autoflush: The autoflush setting to use with newly created
:class:`.Session` objects.
:param autocommit: The autocommit setting to use with newly created
:class:`.Session` objects.
:param expire_on_commit=True: the expire_on_commit setting to use
with newly created :class:`.Session` objects.
:param \**kw: all other keyword arguments are passed to the constructor
of newly created :class:`.Session` objects.
"""
kw['bind'] = bind
kw['autoflush'] = autoflush
kw['autocommit'] = autocommit
kw['expire_on_commit'] = expire_on_commit
self.kw = kw
# make our own subclass of the given class, so that
# events can be associated with it specifically.
self.class_ = type(class_.__name__, (class_,), {})
def __call__(self, **local_kw):
"""Produce a new :class:`.Session` object using the configuration
established in this :class:`.sessionmaker`.
In Python, the ``__call__`` method is invoked on an object when
it is "called" in the same way as a function::
Session = sessionmaker()
session = Session() # invokes sessionmaker.__call__()
"""
for k, v in self.kw.items():
local_kw.setdefault(k, v)
return self.class_(**local_kw)
def configure(self, **new_kw):
"""(Re)configure the arguments for this sessionmaker.
e.g.::
Session = sessionmaker()
Session.configure(bind=create_engine('sqlite://'))
"""
self.kw.update(new_kw)
def __repr__(self):
return "%s(class_=%r%s)" % (
self.__class__.__name__,
self.class_.__name__,
", ".join("%s=%r" % (k, v) for k, v in self.kw.items())
)
_sessions = weakref.WeakValueDictionary()
def make_transient(instance):
"""Make the given instance 'transient'.
This will remove its association with any
session and additionally will remove its "identity key",
such that it's as though the object were newly constructed,
except retaining its values. It also resets the
"deleted" flag on the state if this object
had been explicitly deleted by its session.
Attributes which were "expired" or deferred at the
instance level are reverted to undefined, and
will not trigger any loads.
"""
state = attributes.instance_state(instance)
s = _state_session(state)
if s:
s._expunge_state(state)
# remove expired state and
# deferred callables
state.callables.clear()
if state.key:
del state.key
if state.deleted:
del state.deleted
def object_session(instance):
"""Return the ``Session`` to which instance belongs.
If the instance is not a mapped instance, an error is raised.
"""
try:
return _state_session(attributes.instance_state(instance))
except exc.NO_STATE:
raise exc.UnmappedInstanceError(instance)
def _state_session(state):
if state.session_id:
try:
return _sessions[state.session_id]
except KeyError:
pass
return None
_new_sessionid = util.counter()
|