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Viewing changes to bzrlib/chunk_writer.py

Merge in bzr.dev 3801, resolve NEWS

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bzrlib/chunk_writer.py
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    #    In testing, some values for bzr.dev::
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    #        repack  time  MB   max   full
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    #         1       7.5  4.6  1140  0
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    #         2       8.4  4.2  1036  1          6.8
 
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    #         2       8.4  4.2  1036  1
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    #         3       9.8  4.1  1012  278
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    #         4      10.8  4.1  728   945
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    #        20      11.1  4.1  0     1012
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    #        repack = 0
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    #        zsync   time  MB    repack  max_z   time w/ add_node
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    #         0       6.7  24.7  0       6270    5.0
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    #         1       6.5  13.2  0       3342    4.3
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    #         2       6.6   9.6  0       2414    4.9
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    #         5       6.5   6.2  0       1549    4.8
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    #         6       6.5   5.8  1       1435    4.8
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    #         7       6.6   5.5  19      1337    4.8
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    #         8       6.7   5.3  81      1220    4.4
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    #        10       6.8   5.0  260     967     5.3
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    #        11       6.8   4.9  366     839     5.3
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    #        12       6.9   4.8  454     731     5.1
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    #        15       7.2   4.7  704     450     5.8
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    #        20       7.7   4.6  1133    7       5.8
 
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    #        zsync   time  MB    repack  stop_for_z
 
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    #         0       5.0  24.7  0       6270
 
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    #         1       4.3  13.2  0       3342
 
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    #         2       4.9   9.6  0       2414
 
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    #         5       4.8   6.2  0       1549
 
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    #         6       4.8   5.8  1       1435
 
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    #         7       4.8   5.5  19      1337
 
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    #         8       4.4   5.3  81      1220
 
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    #        10       5.3   5.0  260     967
 
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    #        11       5.3   4.9  366     839
 
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    #        12       5.1   4.8  454     731
 
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    #        15       5.8   4.7  704     450
 
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    #        20       5.8   4.6  1133    7
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    #    In testing, some values for mysql-unpacked::
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    #                next_bytes estim
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    #        repack  time  MB    hit_max full
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    #         1      51.7  15.4  3913  0
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    #         2      54.4  13.7  3467  0         35.4
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    #        20      67.0  13.4  0     3380      46.7
 
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    #        repack  time  MB    full    stop_for_repack
 
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    #         1            15.4  0       3913
 
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    #         2      35.4  13.7  0       346
 
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    #        20      46.7  13.4  3380    0
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    #        repack=0
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    #        zsync                               time w/ add_node
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    #         0      47.7 116.5  0       29782   29.5
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    #         1      48.5  60.2  0       15356   27.8
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    #         2      48.1  42.4  0       10822   27.8
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    #         5      48.3  25.5  0       6491    26.8
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    #         6      48.0  23.2  13      5896    27.3
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    #         7      48.1  21.6  29      5451    27.5
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    #         8      48.1  20.3  52      5108    27.1
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    #        10      46.9  18.6  195     4526    29.4
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    #        11      48.8  18.0  421     4143    29.2
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    #        12      47.4  17.5  702     3738    28.0
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    #        15      49.6  16.5  1223    2969    28.9
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    #        20      48.9  15.7  2182    1810    29.6
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    #        30            15.4  3891    23      31.4
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    _max_repack = 0
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    _max_zsync = 8
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    def __init__(self, chunk_size, reserved=0):
 
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    #        zsync                       stop_for_z
 
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    #         0      29.5 116.5  0       29782
 
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    #         1      27.8  60.2  0       15356
 
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    #         2      27.8  42.4  0       10822
 
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    #         5      26.8  25.5  0       6491
 
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    #         6      27.3  23.2  13      5896
 
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    #         7      27.5  21.6  29      5451
 
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    #         8      27.1  20.3  52      5108
 
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    #        10      29.4  18.6  195     4526
 
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    #        11      29.2  18.0  421     4143
 
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    #        12      28.0  17.5  702     3738
 
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    #        15      28.9  16.5  1223    2969
 
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    #        20      29.6  15.7  2182    1810
 
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    #        30      31.4  15.4  3891    23
 
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    # Tuple of (num_repack_attempts, num_zsync_attempts)
 
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    # num_zsync_attempts only has meaning if num_repack_attempts is 0.
 
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    _repack_opts_for_speed = (0, 8)
 
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    _repack_opts_for_size = (20, 0)
 
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    def __init__(self, chunk_size, reserved=0, optimize_for_size=False):
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        """Create a ChunkWriter to write chunk_size chunks.
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        :param chunk_size: The total byte count to emit at the end of the
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        self.num_zsync = 0
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        self.unused_bytes = None
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        self.reserved_size = reserved
 
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        # Default is to make building fast rather than compact
 
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        self.set_optimize(for_size=optimize_for_size)
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    def finish(self):
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        """Finish the chunk.
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            self.bytes_list.append("\x00" * nulls_needed)
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        return self.bytes_list, self.unused_bytes, nulls_needed
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    def set_optimize(self, for_size=True):
 
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        """Change how we optimize our writes.
 
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        :param for_size: If True, optimize for minimum space usage, otherwise
 
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            optimize for fastest writing speed.
 
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        :return: None
 
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        """
 
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        if for_size:
 
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            opts = ChunkWriter._repack_opts_for_size
 
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        else:
 
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            opts = ChunkWriter._repack_opts_for_speed
 
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        self._max_repack, self._max_zsync = opts
 
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    def _recompress_all_bytes_in(self, extra_bytes=None):
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        """Recompress the current bytes_in, and optionally more.
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