Source code for relstorage.adapters.oracle.oidallocator

##############################################################################
#
# Copyright (c) 2009 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
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"""
IOIDAllocator implementations.
"""

from __future__ import absolute_import

from zope.interface import implementer

from ..._util import metricmethod
from ..interfaces import IOIDAllocator
from ..oidallocator import AbstractRangedOIDAllocator




@implementer(IOIDAllocator)
class OracleOIDAllocator(AbstractRangedOIDAllocator):

    def __init__(self, connmanager):
        self.connmanager = connmanager

    def _set_min_oid_from_range(self, cursor, n):
        """Ensure the next OID is at least the given OID."""
        stmt = "SELECT zoid_seq.nextval FROM DUAL"
        cursor.execute(stmt)
        next_n = cursor.fetchone()[0]
        if next_n < n:
            # Oracle provides no way modify the sequence value
            # except through alter sequence or drop/create sequence,
            # but either statement kills the current transaction.
            # Therefore, open a temporary connection to make the
            # alteration.
            conn2, cursor2 = self.connmanager.open()
            try:
                # Change the sequence by altering the increment.
                # (this is safer than dropping and re-creating the sequence)
                diff = n - next_n
                cursor2.execute(
                    "ALTER SEQUENCE zoid_seq INCREMENT BY %d" % diff)
                cursor2.execute("SELECT zoid_seq.nextval FROM DUAL")
                cursor2.execute("ALTER SEQUENCE zoid_seq INCREMENT BY 1")
                conn2.commit()
            finally:
                self.connmanager.close(conn2, cursor2)



    @metricmethod
    def new_oids(self, cursor):
        """Return a sequence of new, unused OIDs."""
        stmt = "SELECT zoid_seq.nextval FROM DUAL"
        cursor.execute(stmt)
        n = cursor.fetchone()[0]
        return self._oid_range_around(n)


    def reset_oid(self, cursor):
        raise NotImplementedError