#!/usr/bin/env python
#
# Public Domain 2014-present MongoDB, Inc.
# Public Domain 2008-2014 WiredTiger, Inc.
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# This is free and unencumbered software released into the public domain.
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import os, wttest, suite_random
from wiredtiger import stat
from wtdataset import SimpleDataSet
from wtscenario import make_scenarios

# test_truncate19.py
#
# Test to mimic oplog workload in MongoDB. Ensure the deleted pages are
# cleaned up on disk and we are not using excessive disk space.
class test_truncate19(wttest.WiredTigerTestCase):
    conn_config = 'statistics=(all)'
    rand = suite_random.suite_random()

    format_values = [
        ('string_row', dict(key_format='S', value_format='S')),
    ]
    restart = [
        ('restart', dict(restart=True)),
        ('no-restart', dict(restart=False)),
    ]
    scenarios = make_scenarios(format_values, restart)

    def append_rows(self, uri, ds, start_row, nrows, value):
        cursor = self.session.open_cursor(uri)
        self.session.begin_transaction()
        for i in range(start_row, start_row + nrows + 1):
            cursor[ds.key(i)] = value
            if i % 2 == 0:
                self.session.commit_transaction()
                self.session.begin_transaction()
        self.session.commit_transaction()
        cursor.close()

    def do_truncate(self, ds, start_row, nrows):
        self.session.begin_transaction()
        hicursor = self.session.open_cursor(ds.uri)
        hicursor.set_key(ds.key(start_row + nrows))
        self.session.truncate(None, None, hicursor, None)
        self.session.commit_transaction()

    def test_truncate(self):
        uri = 'table:oplog'
        nrows = 1000000

        # Create a table.
        ds = SimpleDataSet(self, uri, 0, key_format=self.key_format, value_format=self.value_format)
        ds.populate()
        ds_dummy = SimpleDataSet(self, 'table:dummy', 0, key_format=self.key_format, value_format=self.value_format)
        ds_dummy.populate()

        value_a = "aaaaa" * 100

        # Write some data
        self.append_rows(uri, ds, 1, nrows, value_a)

        # Reopen the database.
        self.reopen_conn()

        trunc_rows = 0
        start_num = 1
        end_num = nrows
        for i in range(1, 50):
            # Session for checkpoint
            session2 = self.conn.open_session()
            # Session for long running transaction, to make truncate not globally visible
            session3 = self.conn.open_session()
            # Start a long running transaction
            session3.begin_transaction()
            trunc_rows = 10000

            self.do_truncate(ds, start_num, trunc_rows)
            
            # Check stats to make sure we fast-deleted at least one page.
            stat_cursor = self.session.open_cursor('statistics:', None, None)
            fastdelete_pages = stat_cursor[stat.conn.rec_page_delete_fast][2]
  
            self.assertGreater(fastdelete_pages, 0)

            # Take a checkpoint.
            session2.checkpoint()
            # Ensure the datasize is smaller than 600M
            self.assertGreater(600000000, os.path.getsize("oplog.wt"))
            session3.rollback_transaction()
        
            self.append_rows(uri, ds, end_num, trunc_rows, value_a)
            if self.restart:
                session2.checkpoint()
                # Reopen the database.
                self.reopen_conn()

            end_num = end_num + trunc_rows
            start_num = start_num + trunc_rows

        # Ensure the datasize is smaller than 600M
        self.assertGreater(600000000, os.path.getsize("oplog.wt"))

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