test_prepare17.py

#!/usr/bin/env python
#
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# Public Domain 2008-2014 WiredTiger, Inc.
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import wiredtiger, wttest
from wtscenario import make_scenarios
from helper import simulate_crash_restart

# test_prepare17.py
# The following test is to verify that if the out of order commit timestamp(for a transaction, say T2) lies between
# previous commit and durable timestamps(for a transaction, say T1), the durable timestamp of T1 changes to
# the commit timestamp of T2.
class test_prepare17(wttest.WiredTigerTestCase):
    session_config = 'isolation=snapshot'
    uri = 'table:test_prepare17'
    nrows = 1000
    value1 = 'aaaaa'
    value2 = 'bbbbb'

    key_format_values = [
        ('integer-row', dict(key_format='i')),
        ('column', dict(key_format='r')),
    ]
    update = [
        ('prepare', dict(prepare=True)),
        ('non-prepare', dict(prepare=False)),
    ]
    scenarios = make_scenarios(key_format_values, update)

    def test_prepare(self):
        create_params = 'key_format={},value_format=S'.format(self.key_format)
        self.session.create(self.uri, create_params)
        cursor = self.session.open_cursor(self.uri)

        # Transaction one
        self.session.begin_transaction()
        for i in range(1, self.nrows + 1):
            cursor[i] = self.value1
        self.session.prepare_transaction('prepare_timestamp=' + self.timestamp_str(2))
        self.session.commit_transaction('commit_timestamp=' + self.timestamp_str(3)+ ',durable_timestamp=' + self.timestamp_str(6))

        # In the case below, the commit timestamp lies between the previous commit and durable timestamps.
        # Internally, WiredTiger changes the durable timestamp of Transaction one, i.e. 6 to the commit timestamp 
        # of the transaction below, i.e, 4.
        # As per the time window validation the commit timestamp cannot be in between any previous commit and 
        # durable timestamps.
        #
        # Note: The scenario where commit timestamp lies between the previous commit and durable timestamps
        # is not expected from MongoDB, but WiredTiger API can allow it.
        if self.prepare:
            self.session.begin_transaction()
            for i in range(1, self.nrows + 1):
                cursor[i] = self.value2
            self.session.prepare_transaction('prepare_timestamp=' + self.timestamp_str(3))
            self.session.commit_transaction('commit_timestamp=' + self.timestamp_str(4) + ',durable_timestamp=' + self.timestamp_str(7))
        else:
            self.session.begin_transaction()
            for i in range(1, self.nrows + 1):
                cursor[i] = self.value2
            self.session.commit_transaction('commit_timestamp=' + self.timestamp_str(4))

        # Time window validation occurs as part of checkpoint.
        self.session.checkpoint()

    def test_prepare_insert_remove(self):
        if not self.prepare:
            return

        create_params = 'key_format={},value_format=S'.format(self.key_format)
        self.session.create(self.uri, create_params)
        cursor = self.session.open_cursor(self.uri)

        self.session.begin_transaction()
        for i in range(1, self.nrows + 1):
            cursor[i] = self.value1
        self.session.commit_transaction('commit_timestamp=' + self.timestamp_str(2))

        # Transaction 2
        self.session.begin_transaction()
        for i in range(1, self.nrows + 1):
            cursor[i] = self.value2
            cursor.set_key(i)
            cursor.remove()
        self.session.prepare_transaction('prepare_timestamp=' + self.timestamp_str(3))
        self.session.commit_transaction('commit_timestamp=' + self.timestamp_str(4) + ',durable_timestamp=' + self.timestamp_str(7))

        self.conn.set_timestamp('stable_timestamp=' + self.timestamp_str(6))
        self.session.checkpoint()
        simulate_crash_restart(self, ".", "RESTART")

        # Update in Transaction2 should be removed as the stable timestamp (6) is less than the durable timestamp (7).
        cursor = self.session.open_cursor(self.uri)
        self.session.begin_transaction()
        for i in range(1, self.nrows + 1):
            cursor.set_key(i)
            cursor.search()
            self.assertEqual(cursor.get_value(), self.value1)
        self.session.rollback_transaction()