path: root/src/third_party/wiredtiger/test/suite/test_timestamp14.py

#!/usr/bin/env python
#
# Public Domain 2014-2020 MongoDB, Inc.
# Public Domain 2008-2014 WiredTiger, Inc.
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# test_timestamp14.py
#   Global timestamps: oldest reader, all committed, pinned
#

import random
from suite_subprocess import suite_subprocess
import wiredtiger, wttest
from wtscenario import make_scenarios

def timestamp_str(t):
    return '%x' % t

class test_timestamp14(wttest.WiredTigerTestCase, suite_subprocess):
    tablename = 'test_timestamp14'
    uri = 'table:' + tablename
    session_config = 'isolation=snapshot'

    def test_all_durable_old(self):
        # This test was originally for testing the all_committed timestamp.
        # In the absence of prepared transactions, all_durable is identical to
        # all_committed so let's enforce the all_durable values instead.
        all_durable_uri = self.uri + '_all_durable'
        session1 = self.setUpSessionOpen(self.conn)
        session2 = self.setUpSessionOpen(self.conn)
        session1.create(all_durable_uri, 'key_format=i,value_format=i')
        session2.create(all_durable_uri, 'key_format=i,value_format=i')

        # Scenario 0: No commit timestamp has ever been specified therefore
        # There is no all_durable timestamp and we will get an error
        # Querying for it.
        session1.begin_transaction()
        cur1 = session1.open_cursor(all_durable_uri)
        cur1[1]=1
        session1.commit_transaction()
        self.assertRaisesException(wiredtiger.WiredTigerError,
            lambda: self.conn.query_timestamp('get=all_durable'))

        # Scenario 1: A single transaction with a commit timestamp, will
        # result in the all_durable timestamp being set.
        session1.begin_transaction()
        cur1[1]=1
        session1.commit_transaction('commit_timestamp=1')
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "1")

        # Scenario 2: A transaction begins and specifies that it intends
        # to commit at timestamp 2, a second transaction begins and commits
        # at timestamp 3.
        session1.begin_transaction()
        session1.timestamp_transaction('commit_timestamp=2')

        session2.begin_transaction()
        cur2 = session2.open_cursor(all_durable_uri)
        cur2[2] = 2
        session2.commit_transaction('commit_timestamp=3')

        # As the original transaction is still running the all_durable
        # timestamp is being held at 1.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "1")
        cur1[1] = 2
        session1.commit_transaction()

        # Now that the original transaction has finished the all_durable
        # timestamp has moved to 3, skipping 2 as there is a commit with
        # a greater timestamp already existing.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "3")

        # Senario 3: Commit with a commit timestamp of 5 and then begin a
        # transaction intending to commit at 4, the all_durable timestamp
        # should move back to 3. Until the transaction at 4 completes.
        session1.begin_transaction()
        cur1[1] = 3
        session1.commit_transaction('commit_timestamp=5')
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "5")

        session1.begin_transaction()
        # All committed will now move back to 3 as it is the point at which
        # all transactions up to that point have committed.
        session1.timestamp_transaction('commit_timestamp=4')

        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "3")

        session1.commit_transaction()

        # Now that the transaction at timestamp 4 has completed the
        # all committed timestamp is back at 5.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "5")

        # Scenario 4: Holding a transaction open without a commit timestamp
        # Will not affect the all_durable timestamp.
        session1.begin_transaction()
        session2.begin_transaction()
        cur2[2] = 2
        session2.commit_transaction('commit_timestamp=6')

        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "6")
        cur1[1] = 2
        session1.commit_transaction()

    def test_oldest_reader(self):
        oldest_reader_uri = self.uri + '_oldest_reader_pinned'
        session1 = self.setUpSessionOpen(self.conn)
        session2 = self.setUpSessionOpen(self.conn)
        session1.create(oldest_reader_uri, 'key_format=i,value_format=i')
        session2.create(oldest_reader_uri, 'key_format=i,value_format=i')

        # Nothing is reading so there is no oldest reader.
        self.assertRaisesException(wiredtiger.WiredTigerError,
            lambda: self.conn.query_timestamp('get=oldest_reader'))

        # Write some data for reading.
        session1.begin_transaction()
        cur1 = session1.open_cursor(oldest_reader_uri)
        cur1[1]=1
        session1.commit_transaction('commit_timestamp=5')

        # No active sessions so no oldest reader.
        self.assertRaisesException(wiredtiger.WiredTigerError,
            lambda: self.conn.query_timestamp('get=oldest_reader'))

        # Create an active read session.
        session1.begin_transaction('read_timestamp=5')
        # Oldest reader should now exist and be equal to our read timestamp.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=oldest_reader'), '5')

        # Start transaction without read timestamp specified
        # Should not affect the current oldest reader.
        session2.begin_transaction()
        cur2 = session2.open_cursor(oldest_reader_uri)
        cur2[2] = 2

        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=oldest_reader'), '5')

        session2.commit_transaction('commit_timestamp=7')

        # Open read transaction with newer read timestamp, oldest
        # Reader should therefore be unchanged.
        session2.begin_transaction('read_timestamp=7')

        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=oldest_reader'), '5')

        # End current oldest reader transaction, it will have now moved
        # up to our transaction created before.
        session1.commit_transaction()

        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=oldest_reader'), '7')

        session2.commit_transaction()

        # Now that all read transactions have completed we will be back
        # to having no oldest reader.
        self.assertRaisesException(wiredtiger.WiredTigerError,
            lambda: self.conn.query_timestamp('get=oldest_reader'))

    def test_pinned_oldest(self):
        pinned_oldest_uri = self.uri + 'pinned_oldest'
        session1 = self.setUpSessionOpen(self.conn)
        session1.create(pinned_oldest_uri, 'key_format=i,value_format=i')
        # Confirm no oldest timestamp exists.
        self.assertRaisesException(wiredtiger.WiredTigerError,
            lambda: self.conn.query_timestamp('get=oldest'))

        # Confirm no pinned timestamp exists.
        self.assertRaisesException(wiredtiger.WiredTigerError,
            lambda: self.conn.query_timestamp('get=pinned'))

        # Write some data for reading.
        session1.begin_transaction()
        cur1 = session1.open_cursor(pinned_oldest_uri)
        cur1[1]=1
        session1.commit_transaction('commit_timestamp=5')

        # Confirm no oldest timestamp exists.
        self.assertRaisesException(wiredtiger.WiredTigerError,
            lambda: self.conn.query_timestamp('get=oldest'))

        # Confirm no pinned timestamp exists.
        self.assertRaisesException(wiredtiger.WiredTigerError,
            lambda: self.conn.query_timestamp('get=pinned'))

        self.conn.set_timestamp('oldest_timestamp=5')

        # Pinned timestamp should now match oldest timestamp
        self.assertTimestampsEqual(self.conn.query_timestamp('get=pinned'), '5')

        # Write some more data for reading.
        session1.begin_transaction()
        cur1[2]=2
        session1.commit_transaction('commit_timestamp=8')

        # Create an active read session.
        session1.begin_transaction('read_timestamp=5')

        # Move oldest timestamp past active read session.
        self.conn.set_timestamp('oldest_timestamp=8')

        # Pinned timestamp should now reflect oldest reader.
        self.assertTimestampsEqual(self.conn.query_timestamp('get=pinned'), '5')

        # End active read session.
        session1.commit_transaction()

        # Pinned timestamp should now match oldest timestamp.
        self.assertTimestampsEqual(self.conn.query_timestamp('get=pinned'), '8')

    def test_all_durable(self):
        all_durable_uri = self.uri + '_all_durable'
        session1 = self.setUpSessionOpen(self.conn)
        session1.create(all_durable_uri, 'key_format=i,value_format=i')

        # Since this is a non-prepared transaction, we'll be using the commit
        # timestamp when calculating all_durable since it's implied that they're
        # the same thing.
        session1.begin_transaction()
        cur1 = session1.open_cursor(all_durable_uri)
        cur1[1] = 1
        session1.commit_transaction('commit_timestamp=3')
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '3')

        # We have a running transaction with a lower commit_timestamp than we've
        # seen before. So all_durable should return (lowest commit timestamp - 1).
        session1.begin_transaction()
        cur1[2] = 2
        session1.timestamp_transaction('commit_timestamp=2')
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '1')
        session1.commit_transaction()

        # After committing, go back to the value we saw previously.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '3')

        # For prepared transactions, we take into account the durable timestamp
        # when calculating all_durable.
        session1.begin_transaction()
        cur1[3] = 3
        session1.prepare_transaction('prepare_timestamp=6')

        # If we have a commit timestamp for a prepared transaction, then we
        # don't want that to be visible in the all_durable calculation.
        session1.timestamp_transaction('commit_timestamp=7')
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '3')

        # Now take into account the durable timestamp.
        session1.timestamp_transaction('durable_timestamp=8')
        session1.commit_transaction()
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '8')

        # All durable moves back when we have a running prepared transaction
        # with a lower durable timestamp than has previously been committed.
        session1.begin_transaction()
        cur1[4] = 4
        session1.prepare_transaction('prepare_timestamp=3')

        # If we have a commit timestamp for a prepared transaction, then we
        # don't want that to be visible in the all_durable calculation.
        session1.timestamp_transaction('commit_timestamp=4')
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '8')

        # Now take into account the durable timestamp.
        session1.timestamp_transaction('durable_timestamp=5')
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '4')
        session1.commit_transaction()

        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '8')

        # Now test a scenario with multiple commit timestamps for a single txn.
        session1.begin_transaction()
        cur1[5] = 5
        session1.timestamp_transaction('commit_timestamp=6')
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '5')

        # Make more changes and set a new commit timestamp.
        # Our calculation should use the first commit timestamp so there should
        # be no observable difference to the all_durable value.
        cur1[6] = 6
        session1.timestamp_transaction('commit_timestamp=7')
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '5')

        # Once committed, we go back to 8.
        session1.commit_transaction()
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), '8')

    def test_all(self):
        all_uri = self.uri + 'pinned_oldest'
        session1 = self.setUpSessionOpen(self.conn)
        session2 = self.setUpSessionOpen(self.conn)
        session1.create(all_uri, 'key_format=i,value_format=i')
        session2.create(all_uri, 'key_format=i,value_format=i')
        cur1 = session1.open_cursor(all_uri)
        cur2 = session2.open_cursor(all_uri)
        # Set up oldest timestamp.
        self.conn.set_timestamp('oldest_timestamp=1')

        # Write some data for reading.

        session1.begin_transaction()
        cur1[1]=1
        session1.commit_transaction('commit_timestamp=2')
        session1.begin_transaction()
        cur1[2]=2
        session1.commit_transaction('commit_timestamp=4')
        # Confirm all_durable is now 4.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "4")

        # Create a read session.
        session1.begin_transaction('read_timestamp=2')
        # Confirm oldest reader is 2 and the the value we read is 1.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=oldest_reader'), "2")

        self.assertEqual(cur1[1], 1)
        # Commit some data at timestamp 7.
        session2.begin_transaction()
        cur2[3] = 2
        session2.commit_transaction('commit_timestamp=7')
        # All_durable should now be 7.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "7")

        # Move oldest to 5.
        self.conn.set_timestamp('oldest_timestamp=5')

        # Confirm pinned timestamp is pointing at oldest_reader.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=pinned'),
            self.conn.query_timestamp('get=oldest_reader'))

        # Begin a write transaction pointing at timestamp 6,
        # this is below our current all_durable so it should move back
        # to the oldest timestamp.
        session2.begin_transaction()
        session2.timestamp_transaction('commit_timestamp=6')
        cur2[4] = 3

        # Confirm all_durable is now equal to oldest.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'),
            self.conn.query_timestamp('get=oldest'))

        session2.commit_transaction()
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=all_durable'), "7")
        # End our read transaction.
        session1.commit_transaction()

        # Pinned will now match oldest.
        self.assertTimestampsEqual(
            self.conn.query_timestamp('get=pinned'),
            self.conn.query_timestamp('get=oldest'))

if __name__ == '__main__':
    wttest.run()