#!/usr/bin/env python
#
# Public Domain 2014-2016 MongoDB, Inc.
# Public Domain 2008-2014 WiredTiger, Inc.
#
# This is free and unencumbered software released into the public domain.
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# of this software dedicate any and all copyright interest in the
# software to the public domain. We make this dedication for the benefit
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# software under copyright law.
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import os
import wiredtiger, wttest
from helper import key_populate
from wtscenario import check_scenarios

# test_empty.py
#       Test that empty objects don't write anything other than a single sector.
class test_empty(wttest.WiredTigerTestCase):
    name = 'test_empty'

    scenarios = check_scenarios([
        ('file-r', dict(type='file:', fmt='r')),
        ('file-S', dict(type='file:', fmt='S')),
        ('table-r', dict(type='table:', fmt='r')),
        ('table-S', dict(type='table:', fmt='S'))
    ])

    # Creating an object and then closing it shouldn't write any blocks.
    def test_empty_create(self):
        uri = self.type + self.name
        self.session.create(uri, 'key_format=' + self.fmt)
        self.session.close()
        name = self.name
        if self.type == "table:":
            name = name + '.wt'
        self.assertEquals(os.stat(name).st_size, 4*1024)

    # Open a new sesssion, add a few rows to an object and then remove them,
    # then close the object.  We open/close the object so it's flushed from
    # the underlying cache each time.
    def empty(self):
        uri = self.type + self.name
        self.session = self.conn.open_session()
        self.session.create(uri, 'key_format=' + self.fmt)

        # Add a few records to the object and remove them.
        cursor = self.session.open_cursor(uri, None, None)
        for i in range(1,5):
            key = key_populate(cursor, i)
            cursor[key] = "XXX"
            del cursor[key]

        # Perform a checkpoint (we shouldn't write any underlying pages because
        # of a checkpoint, either).
        self.session.checkpoint("name=ckpt")

        # Open and close a checkpoint cursor.
        cursor = self.session.open_cursor(uri, None, "checkpoint=ckpt")
        cursor.close()

        self.session.close()

        # The file should not have grown.
        name = self.name
        if self.type == "table:":
            name = name + '.wt'
        self.assertEquals(os.stat(name).st_size, 4*1024)

    # Creating an object, inserting and removing records (that is, building an
    # empty, dirty tree), shouldn't write any blocks.  This doesn't work for
    # column-store objects, though, because deleting an object modifies the name
    # space, which requires a write.
    def test_empty(self):
        if self.fmt == 'r':
            return

        for i in range(1,5):
            self.empty()

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