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# Copyright (C) 2008 Canonical Ltd
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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from bisect import bisect_right
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from bzrlib.index import _OPTION_NODE_REFS, _OPTION_KEY_ELEMENTS, _OPTION_LEN
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from bzrlib.transport import get_transport
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_BTSIGNATURE = "B+Tree Graph Index 2\n"
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_OPTION_ROW_LENGTHS = "row_lengths="
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_LEAF_FLAG = "type=leaf\n"
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_INTERNAL_FLAG = "type=internal\n"
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_INTERNAL_OFFSET = "offset="
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_RESERVED_HEADER_BYTES = 120
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# 4K per page: 4MB - 1000 entries
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_NODE_CACHE_SIZE = 1000
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class _BuilderRow(object):
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"""The stored state accumulated while writing out a row in the index.
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:ivar spool: A temporary file used to accumulate nodes for this row
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:ivar nodes: The count of nodes emitted so far.
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"""Create a _BuilderRow."""
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self.spool = None# tempfile.TemporaryFile(prefix='bzr-index-row-')
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def finish_node(self, pad=True):
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byte_lines, _, padding = self.writer.finish()
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self.spool = cStringIO.StringIO()
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self.spool.write("\x00" * _RESERVED_HEADER_BYTES)
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# We got bigger than 1 node, switch to a temp file
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spool = tempfile.TemporaryFile(prefix='bzr-index-row-')
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spool.write(self.spool.getvalue())
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if not pad and padding:
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skipped_bytes = padding
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self.spool.writelines(byte_lines)
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remainder = (self.spool.tell() + skipped_bytes) % _PAGE_SIZE
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raise AssertionError("incorrect node length: %d, %d"
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% (self.spool.tell(), remainder))
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class _InternalBuilderRow(_BuilderRow):
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"""The stored state accumulated while writing out internal rows."""
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def finish_node(self, pad=True):
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raise AssertionError("Must pad internal nodes only.")
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_BuilderRow.finish_node(self)
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class _LeafBuilderRow(_BuilderRow):
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"""The stored state accumulated while writing out a leaf rows."""
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class BTreeBuilder(index.GraphIndexBuilder):
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"""A Builder for B+Tree based Graph indices.
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The resulting graph has the structure:
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_SIGNATURE OPTIONS NODES
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_SIGNATURE := 'B+Tree Graph Index 1' NEWLINE
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OPTIONS := REF_LISTS KEY_ELEMENTS LENGTH
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REF_LISTS := 'node_ref_lists=' DIGITS NEWLINE
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KEY_ELEMENTS := 'key_elements=' DIGITS NEWLINE
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LENGTH := 'len=' DIGITS NEWLINE
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ROW_LENGTHS := 'row_lengths' DIGITS (COMMA DIGITS)*
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NODES := NODE_COMPRESSED*
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NODE_COMPRESSED:= COMPRESSED_BYTES{4096}
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NODE_RAW := INTERNAL | LEAF
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INTERNAL := INTERNAL_FLAG POINTERS
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LEAF := LEAF_FLAG ROWS
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KEY_ELEMENT := Not-whitespace-utf8
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KEY := KEY_ELEMENT (NULL KEY_ELEMENT)*
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ROW := KEY NULL ABSENT? NULL REFERENCES NULL VALUE NEWLINE
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REFERENCES := REFERENCE_LIST (TAB REFERENCE_LIST){node_ref_lists - 1}
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REFERENCE_LIST := (REFERENCE (CR REFERENCE)*)?
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VALUE := no-newline-no-null-bytes
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def __init__(self, reference_lists=0, key_elements=1, spill_at=100000):
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"""See GraphIndexBuilder.__init__.
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:param spill_at: Optional parameter controlling the maximum number
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of nodes that BTreeBuilder will hold in memory.
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index.GraphIndexBuilder.__init__(self, reference_lists=reference_lists,
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key_elements=key_elements)
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self._spill_at = spill_at
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self._backing_indices = []
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# A map of {key: (node_refs, value)}
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# Indicate it hasn't been built yet
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self._nodes_by_key = None
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self._optimize_for_size = False
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def add_node(self, key, value, references=()):
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"""Add a node to the index.
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If adding the node causes the builder to reach its spill_at threshold,
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disk spilling will be triggered.
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:param key: The key. keys are non-empty tuples containing
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as many whitespace-free utf8 bytestrings as the key length
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defined for this index.
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:param references: An iterable of iterables of keys. Each is a
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reference to another key.
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:param value: The value to associate with the key. It may be any
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bytes as long as it does not contain \0 or \n.
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# we don't care about absent_references
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node_refs, _ = self._check_key_ref_value(key, references, value)
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if key in self._nodes:
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raise errors.BadIndexDuplicateKey(key, self)
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self._nodes[key] = (node_refs, value)
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if self._nodes_by_key is not None and self._key_length > 1:
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self._update_nodes_by_key(key, value, node_refs)
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if len(self._keys) < self._spill_at:
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self._spill_mem_keys_to_disk()
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def _spill_mem_keys_to_disk(self):
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"""Write the in memory keys down to disk to cap memory consumption.
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If we already have some keys written to disk, we will combine them so
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as to preserve the sorted order. The algorithm for combining uses
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powers of two. So on the first spill, write all mem nodes into a
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single index. On the second spill, combine the mem nodes with the nodes
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on disk to create a 2x sized disk index and get rid of the first index.
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On the third spill, create a single new disk index, which will contain
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the mem nodes, and preserve the existing 2x sized index. On the fourth,
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combine mem with the first and second indexes, creating a new one of
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size 4x. On the fifth create a single new one, etc.
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if self._combine_backing_indices:
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(new_backing_file, size,
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backing_pos) = self._spill_mem_keys_and_combine()
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new_backing_file, size = self._spill_mem_keys_without_combining()
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# Note: The transport here isn't strictly needed, because we will use
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# direct access to the new_backing._file object
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new_backing = BTreeGraphIndex(get_transport('.'), '<temp>', size)
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# GC will clean up the file
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new_backing._file = new_backing_file
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if self._combine_backing_indices:
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if len(self._backing_indices) == backing_pos:
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self._backing_indices.append(None)
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self._backing_indices[backing_pos] = new_backing
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for backing_pos in range(backing_pos):
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self._backing_indices[backing_pos] = None
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self._backing_indices.append(new_backing)
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self._nodes_by_key = None
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def _spill_mem_keys_without_combining(self):
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return self._write_nodes(self._iter_mem_nodes(), allow_optimize=False)
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def _spill_mem_keys_and_combine(self):
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iterators_to_combine = [self._iter_mem_nodes()]
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for pos, backing in enumerate(self._backing_indices):
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iterators_to_combine.append(backing.iter_all_entries())
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backing_pos = pos + 1
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new_backing_file, size = \
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self._write_nodes(self._iter_smallest(iterators_to_combine),
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allow_optimize=False)
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return new_backing_file, size, backing_pos
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def add_nodes(self, nodes):
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"""Add nodes to the index.
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:param nodes: An iterable of (key, node_refs, value) entries to add.
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if self.reference_lists:
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for (key, value, node_refs) in nodes:
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self.add_node(key, value, node_refs)
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for (key, value) in nodes:
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self.add_node(key, value)
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def _iter_mem_nodes(self):
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"""Iterate over the nodes held in memory."""
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if self.reference_lists:
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for key in sorted(nodes):
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references, value = nodes[key]
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yield self, key, value, references
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for key in sorted(nodes):
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references, value = nodes[key]
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yield self, key, value
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def _iter_smallest(self, iterators_to_combine):
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if len(iterators_to_combine) == 1:
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for value in iterators_to_combine[0]:
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for iterator in iterators_to_combine:
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current_values.append(iterator.next())
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except StopIteration:
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current_values.append(None)
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# Decorate candidates with the value to allow 2.4's min to be used.
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candidates = [(item[1][1], item) for item
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in enumerate(current_values) if item[1] is not None]
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if not len(candidates):
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selected = min(candidates)
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# undecorate back to (pos, node)
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selected = selected[1]
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if last == selected[1][1]:
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raise errors.BadIndexDuplicateKey(last, self)
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last = selected[1][1]
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# Yield, with self as the index
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yield (self,) + selected[1][1:]
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current_values[pos] = iterators_to_combine[pos].next()
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except StopIteration:
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current_values[pos] = None
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def _add_key(self, string_key, line, rows, allow_optimize=True):
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"""Add a key to the current chunk.
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:param string_key: The key to add.
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:param line: The fully serialised key and value.
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:param allow_optimize: If set to False, prevent setting the optimize
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flag when writing out. This is used by the _spill_mem_keys_to_disk
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if rows[-1].writer is None:
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# opening a new leaf chunk;
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for pos, internal_row in enumerate(rows[:-1]):
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# flesh out any internal nodes that are needed to
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# preserve the height of the tree
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if internal_row.writer is None:
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if internal_row.nodes == 0:
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length -= _RESERVED_HEADER_BYTES # padded
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optimize_for_size = self._optimize_for_size
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optimize_for_size = False
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internal_row.writer = chunk_writer.ChunkWriter(length, 0,
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optimize_for_size=optimize_for_size)
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internal_row.writer.write(_INTERNAL_FLAG)
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internal_row.writer.write(_INTERNAL_OFFSET +
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str(rows[pos + 1].nodes) + "\n")
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if rows[-1].nodes == 0:
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length -= _RESERVED_HEADER_BYTES # padded
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rows[-1].writer = chunk_writer.ChunkWriter(length,
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optimize_for_size=self._optimize_for_size)
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rows[-1].writer.write(_LEAF_FLAG)
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if rows[-1].writer.write(line):
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# this key did not fit in the node:
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rows[-1].finish_node()
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key_line = string_key + "\n"
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for row in reversed(rows[:-1]):
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# Mark the start of the next node in the node above. If it
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# doesn't fit then propagate upwards until we find one that
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if row.writer.write(key_line):
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# We've found a node that can handle the pointer.
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# If we reached the current root without being able to mark the
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# division point, then we need a new root:
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if 'index' in debug.debug_flags:
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trace.mutter('Inserting new global row.')
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new_row = _InternalBuilderRow()
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rows.insert(0, new_row)
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# This will be padded, hence the -100
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new_row.writer = chunk_writer.ChunkWriter(
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_PAGE_SIZE - _RESERVED_HEADER_BYTES,
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optimize_for_size=self._optimize_for_size)
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new_row.writer.write(_INTERNAL_FLAG)
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new_row.writer.write(_INTERNAL_OFFSET +
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str(rows[1].nodes - 1) + "\n")
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new_row.writer.write(key_line)
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self._add_key(string_key, line, rows, allow_optimize=allow_optimize)
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def _write_nodes(self, node_iterator, allow_optimize=True):
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"""Write node_iterator out as a B+Tree.
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:param node_iterator: An iterator of sorted nodes. Each node should
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match the output given by iter_all_entries.
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:param allow_optimize: If set to False, prevent setting the optimize
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flag when writing out. This is used by the _spill_mem_keys_to_disk
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:return: A file handle for a temporary file containing a B+Tree for
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# The index rows - rows[0] is the root, rows[1] is the layer under it
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# forward sorted by key. In future we may consider topological sorting,
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# at the cost of table scans for direct lookup, or a second index for
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# A stack with the number of nodes of each size. 0 is the root node
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# and must always be 1 (if there are any nodes in the tree).
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self.row_lengths = []
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# Loop over all nodes adding them to the bottom row
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# (rows[-1]). When we finish a chunk in a row,
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# propagate the key that didn't fit (comes after the chunk) to the
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# row above, transitively.
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for node in node_iterator:
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# First key triggers the first row
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rows.append(_LeafBuilderRow())
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string_key, line = _btree_serializer._flatten_node(node,
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self.reference_lists)
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self._add_key(string_key, line, rows, allow_optimize=allow_optimize)
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for row in reversed(rows):
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pad = (type(row) != _LeafBuilderRow)
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row.finish_node(pad=pad)
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lines = [_BTSIGNATURE]
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lines.append(_OPTION_NODE_REFS + str(self.reference_lists) + '\n')
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lines.append(_OPTION_KEY_ELEMENTS + str(self._key_length) + '\n')
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lines.append(_OPTION_LEN + str(key_count) + '\n')
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row_lengths = [row.nodes for row in rows]
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lines.append(_OPTION_ROW_LENGTHS + ','.join(map(str, row_lengths)) + '\n')
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if row_lengths and row_lengths[-1] > 1:
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result = tempfile.NamedTemporaryFile(prefix='bzr-index-')
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result = cStringIO.StringIO()
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result.writelines(lines)
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position = sum(map(len, lines))
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if position > _RESERVED_HEADER_BYTES:
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raise AssertionError("Could not fit the header in the"
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" reserved space: %d > %d"
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% (position, _RESERVED_HEADER_BYTES))
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# write the rows out:
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reserved = _RESERVED_HEADER_BYTES # reserved space for first node
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# copy nodes to the finalised file.
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# Special case the first node as it may be prefixed
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node = row.spool.read(_PAGE_SIZE)
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result.write(node[reserved:])
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result.write("\x00" * (reserved - position))
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position = 0 # Only the root row actually has an offset
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copied_len = osutils.pumpfile(row.spool, result)
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if copied_len != (row.nodes - 1) * _PAGE_SIZE:
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if type(row) != _LeafBuilderRow:
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raise AssertionError("Incorrect amount of data copied"
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" expected: %d, got: %d"
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% ((row.nodes - 1) * _PAGE_SIZE,
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"""Finalise the index.
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:return: A file handle for a temporary file containing the nodes added
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return self._write_nodes(self.iter_all_entries())[0]
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def iter_all_entries(self):
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"""Iterate over all keys within the index
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:return: An iterable of (index, key, value, reference_lists). There is
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no defined order for the result iteration - it will be in the most
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efficient order for the index (in this case dictionary hash order).
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if 'evil' in debug.debug_flags:
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trace.mutter_callsite(3,
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"iter_all_entries scales with size of history.")
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# Doing serial rather than ordered would be faster; but this shouldn't
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# be getting called routinely anyway.
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iterators = [self._iter_mem_nodes()]
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for backing in self._backing_indices:
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if backing is not None:
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iterators.append(backing.iter_all_entries())
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if len(iterators) == 1:
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return self._iter_smallest(iterators)
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def iter_entries(self, keys):
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"""Iterate over keys within the index.
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:param keys: An iterable providing the keys to be retrieved.
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:return: An iterable of (index, key, value, reference_lists). There is no
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defined order for the result iteration - it will be in the most
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efficient order for the index (keys iteration order in this case).
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local_keys = keys.intersection(self._keys)
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if self.reference_lists:
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for key in local_keys:
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node = self._nodes[key]
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yield self, key, node[1], node[0]
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for key in local_keys:
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node = self._nodes[key]
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yield self, key, node[1]
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# Find things that are in backing indices that have not been handled
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if not self._backing_indices:
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return # We won't find anything there either
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# Remove all of the keys that we found locally
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keys.difference_update(local_keys)
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for backing in self._backing_indices:
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for node in backing.iter_entries(keys):
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yield (self,) + node[1:]
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def iter_entries_prefix(self, keys):
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"""Iterate over keys within the index using prefix matching.
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Prefix matching is applied within the tuple of a key, not to within
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the bytestring of each key element. e.g. if you have the keys ('foo',
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'bar'), ('foobar', 'gam') and do a prefix search for ('foo', None) then
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only the former key is returned.
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:param keys: An iterable providing the key prefixes to be retrieved.
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Each key prefix takes the form of a tuple the length of a key, but
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with the last N elements 'None' rather than a regular bytestring.
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The first element cannot be 'None'.
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:return: An iterable as per iter_all_entries, but restricted to the
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keys with a matching prefix to those supplied. No additional keys
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will be returned, and every match that is in the index will be
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# XXX: To much duplication with the GraphIndex class; consider finding
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# a good place to pull out the actual common logic.
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for backing in self._backing_indices:
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for node in backing.iter_entries_prefix(keys):
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yield (self,) + node[1:]
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if self._key_length == 1:
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raise errors.BadIndexKey(key)
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if len(key) != self._key_length:
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raise errors.BadIndexKey(key)
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node = self._nodes[key]
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if self.reference_lists:
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yield self, key, node[1], node[0]
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yield self, key, node[1]
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raise errors.BadIndexKey(key)
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if len(key) != self._key_length:
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raise errors.BadIndexKey(key)
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# find what it refers to:
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key_dict = self._get_nodes_by_key()
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# find the subdict to return
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while len(elements) and elements[0] is not None:
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key_dict = key_dict[elements[0]]
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# a non-existant lookup.
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key_dict = dicts.pop(-1)
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# can't be empty or would not exist
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item, value = key_dict.iteritems().next()
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if type(value) == dict:
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dicts.extend(key_dict.itervalues())
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for value in key_dict.itervalues():
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yield (self, ) + value
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yield (self, ) + key_dict
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def _get_nodes_by_key(self):
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if self._nodes_by_key is None:
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if self.reference_lists:
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for key, (references, value) in self._nodes.iteritems():
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key_dict = nodes_by_key
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for subkey in key[:-1]:
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key_dict = key_dict.setdefault(subkey, {})
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key_dict[key[-1]] = key, value, references
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for key, (references, value) in self._nodes.iteritems():
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key_dict = nodes_by_key
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for subkey in key[:-1]:
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key_dict = key_dict.setdefault(subkey, {})
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key_dict[key[-1]] = key, value
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self._nodes_by_key = nodes_by_key
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return self._nodes_by_key
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"""Return an estimate of the number of keys in this index.
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For InMemoryGraphIndex the estimate is exact.
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return len(self._keys) + sum(backing.key_count() for backing in
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self._backing_indices if backing is not None)
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"""In memory index's have no known corruption at the moment."""
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class _LeafNode(object):
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"""A leaf node for a serialised B+Tree index."""
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__slots__ = ('keys', 'min_key', 'max_key')
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def __init__(self, bytes, key_length, ref_list_length):
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"""Parse bytes to create a leaf node object."""
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# splitlines mangles the \r delimiters.. don't use it.
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key_list = _btree_serializer._parse_leaf_lines(bytes,
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key_length, ref_list_length)
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self.min_key = key_list[0][0]
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self.max_key = key_list[-1][0]
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self.min_key = self.max_key = None
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self.keys = dict(key_list)
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class _InternalNode(object):
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"""An internal node for a serialised B+Tree index."""
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__slots__ = ('keys', 'offset')
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def __init__(self, bytes):
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"""Parse bytes to create an internal node object."""
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# splitlines mangles the \r delimiters.. don't use it.
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self.keys = self._parse_lines(bytes.split('\n'))
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def _parse_lines(self, lines):
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self.offset = int(lines[1][7:])
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for line in lines[2:]:
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# TODO: Switch to StaticTuple here.
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nodes.append(tuple(map(intern, line.split('\0'))))
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class BTreeGraphIndex(object):
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"""Access to nodes via the standard GraphIndex interface for B+Tree's.
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Individual nodes are held in a LRU cache. This holds the root node in
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memory except when very large walks are done.
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def __init__(self, transport, name, size):
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"""Create a B+Tree index object on the index name.
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:param transport: The transport to read data for the index from.
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:param name: The file name of the index on transport.
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:param size: Optional size of the index in bytes. This allows
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compatibility with the GraphIndex API, as well as ensuring that
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the initial read (to read the root node header) can be done
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without over-reading even on empty indices, and on small indices
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allows single-IO to read the entire index.
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self._transport = transport
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self._recommended_pages = self._compute_recommended_pages()
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self._root_node = None
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# Default max size is 100,000 leave values
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self._leaf_value_cache = None # lru_cache.LRUCache(100*1000)
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self._leaf_node_cache = lru_cache.LRUCache(_NODE_CACHE_SIZE)
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# We could limit this, but even a 300k record btree has only 3k leaf
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# nodes, and only 20 internal nodes. So the default of 100 nodes in an
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# LRU would mean we always cache everything anyway, no need to pay the
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self._internal_node_cache = fifo_cache.FIFOCache(100)
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self._key_count = None
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self._row_lengths = None
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self._row_offsets = None # Start of each row, [-1] is the end
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def __eq__(self, other):
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"""Equal when self and other were created with the same parameters."""
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type(self) == type(other) and
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self._transport == other._transport and
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self._name == other._name and
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self._size == other._size)
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def __ne__(self, other):
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return not self.__eq__(other)
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def _get_and_cache_nodes(self, nodes):
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"""Read nodes and cache them in the lru.
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The nodes list supplied is sorted and then read from disk, each node
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being inserted it into the _node_cache.
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Note: Asking for more nodes than the _node_cache can contain will
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result in some of the results being immediately discarded, to prevent
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this an assertion is raised if more nodes are asked for than are
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:return: A dict of {node_pos: node}
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start_of_leaves = None
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for node_pos, node in self._read_nodes(sorted(nodes)):
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if node_pos == 0: # Special case
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self._root_node = node
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if start_of_leaves is None:
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start_of_leaves = self._row_offsets[-2]
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if node_pos < start_of_leaves:
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self._internal_node_cache.add(node_pos, node)
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self._leaf_node_cache.add(node_pos, node)
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found[node_pos] = node
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def _compute_recommended_pages(self):
710
"""Convert transport's recommended_page_size into btree pages.
712
recommended_page_size is in bytes, we want to know how many _PAGE_SIZE
713
pages fit in that length.
715
recommended_read = self._transport.recommended_page_size()
716
recommended_pages = int(math.ceil(recommended_read /
718
return recommended_pages
720
def _compute_total_pages_in_index(self):
721
"""How many pages are in the index.
723
If we have read the header we will use the value stored there.
724
Otherwise it will be computed based on the length of the index.
726
if self._size is None:
727
raise AssertionError('_compute_total_pages_in_index should not be'
728
' called when self._size is None')
729
if self._root_node is not None:
730
# This is the number of pages as defined by the header
731
return self._row_offsets[-1]
732
# This is the number of pages as defined by the size of the index. They
733
# should be indentical.
734
total_pages = int(math.ceil(self._size / float(_PAGE_SIZE)))
737
def _expand_offsets(self, offsets):
738
"""Find extra pages to download.
740
The idea is that we always want to make big-enough requests (like 64kB
741
for http), so that we don't waste round trips. So given the entries
742
that we already have cached and the new pages being downloaded figure
743
out what other pages we might want to read.
745
See also doc/developers/btree_index_prefetch.txt for more details.
747
:param offsets: The offsets to be read
748
:return: A list of offsets to download
750
if 'index' in debug.debug_flags:
751
trace.mutter('expanding: %s\toffsets: %s', self._name, offsets)
753
if len(offsets) >= self._recommended_pages:
754
# Don't add more, we are already requesting more than enough
755
if 'index' in debug.debug_flags:
756
trace.mutter(' not expanding large request (%s >= %s)',
757
len(offsets), self._recommended_pages)
759
if self._size is None:
760
# Don't try anything, because we don't know where the file ends
761
if 'index' in debug.debug_flags:
762
trace.mutter(' not expanding without knowing index size')
764
total_pages = self._compute_total_pages_in_index()
765
cached_offsets = self._get_offsets_to_cached_pages()
766
# If reading recommended_pages would read the rest of the index, just
768
if total_pages - len(cached_offsets) <= self._recommended_pages:
769
# Read whatever is left
771
expanded = [x for x in xrange(total_pages)
772
if x not in cached_offsets]
774
expanded = range(total_pages)
775
if 'index' in debug.debug_flags:
776
trace.mutter(' reading all unread pages: %s', expanded)
779
if self._root_node is None:
780
# ATM on the first read of the root node of a large index, we don't
781
# bother pre-reading any other pages. This is because the
782
# likelyhood of actually reading interesting pages is very low.
783
# See doc/developers/btree_index_prefetch.txt for a discussion, and
784
# a possible implementation when we are guessing that the second
785
# layer index is small
786
final_offsets = offsets
788
tree_depth = len(self._row_lengths)
789
if len(cached_offsets) < tree_depth and len(offsets) == 1:
790
# We haven't read enough to justify expansion
791
# If we are only going to read the root node, and 1 leaf node,
792
# then it isn't worth expanding our request. Once we've read at
793
# least 2 nodes, then we are probably doing a search, and we
794
# start expanding our requests.
795
if 'index' in debug.debug_flags:
796
trace.mutter(' not expanding on first reads')
798
final_offsets = self._expand_to_neighbors(offsets, cached_offsets,
801
final_offsets = sorted(final_offsets)
802
if 'index' in debug.debug_flags:
803
trace.mutter('expanded: %s', final_offsets)
806
def _expand_to_neighbors(self, offsets, cached_offsets, total_pages):
807
"""Expand requests to neighbors until we have enough pages.
809
This is called from _expand_offsets after policy has determined that we
811
We only want to expand requests within a given layer. We cheat a little
812
bit and assume all requests will be in the same layer. This is true
813
given the current design, but if it changes this algorithm may perform
816
:param offsets: requested offsets
817
:param cached_offsets: offsets for pages we currently have cached
818
:return: A set() of offsets after expansion
820
final_offsets = set(offsets)
822
new_tips = set(final_offsets)
823
while len(final_offsets) < self._recommended_pages and new_tips:
827
first, end = self._find_layer_first_and_end(pos)
830
and previous not in cached_offsets
831
and previous not in final_offsets
832
and previous >= first):
833
next_tips.add(previous)
835
if (after < total_pages
836
and after not in cached_offsets
837
and after not in final_offsets
840
# This would keep us from going bigger than
841
# recommended_pages by only expanding the first offsets.
842
# However, if we are making a 'wide' request, it is
843
# reasonable to expand all points equally.
844
# if len(final_offsets) > recommended_pages:
846
final_offsets.update(next_tips)
850
def external_references(self, ref_list_num):
851
if self._root_node is None:
852
self._get_root_node()
853
if ref_list_num + 1 > self.node_ref_lists:
854
raise ValueError('No ref list %d, index has %d ref lists'
855
% (ref_list_num, self.node_ref_lists))
858
for node in self.iter_all_entries():
860
refs.update(node[3][ref_list_num])
863
def _find_layer_first_and_end(self, offset):
864
"""Find the start/stop nodes for the layer corresponding to offset.
866
:return: (first, end)
867
first is the first node in this layer
868
end is the first node of the next layer
871
for roffset in self._row_offsets:
878
def _get_offsets_to_cached_pages(self):
879
"""Determine what nodes we already have cached."""
880
cached_offsets = set(self._internal_node_cache.keys())
881
cached_offsets.update(self._leaf_node_cache.keys())
882
if self._root_node is not None:
883
cached_offsets.add(0)
884
return cached_offsets
886
def _get_root_node(self):
887
if self._root_node is None:
888
# We may not have a root node yet
889
self._get_internal_nodes([0])
890
return self._root_node
892
def _get_nodes(self, cache, node_indexes):
895
for idx in node_indexes:
896
if idx == 0 and self._root_node is not None:
897
found[0] = self._root_node
900
found[idx] = cache[idx]
905
needed = self._expand_offsets(needed)
906
found.update(self._get_and_cache_nodes(needed))
909
def _get_internal_nodes(self, node_indexes):
910
"""Get a node, from cache or disk.
912
After getting it, the node will be cached.
914
return self._get_nodes(self._internal_node_cache, node_indexes)
916
def _cache_leaf_values(self, nodes):
917
"""Cache directly from key => value, skipping the btree."""
918
if self._leaf_value_cache is not None:
919
for node in nodes.itervalues():
920
for key, value in node.keys.iteritems():
921
if key in self._leaf_value_cache:
922
# Don't add the rest of the keys, we've seen this node
925
self._leaf_value_cache[key] = value
927
def _get_leaf_nodes(self, node_indexes):
928
"""Get a bunch of nodes, from cache or disk."""
929
found = self._get_nodes(self._leaf_node_cache, node_indexes)
930
self._cache_leaf_values(found)
933
def iter_all_entries(self):
934
"""Iterate over all keys within the index.
936
:return: An iterable of (index, key, value) or (index, key, value, reference_lists).
937
The former tuple is used when there are no reference lists in the
938
index, making the API compatible with simple key:value index types.
939
There is no defined order for the result iteration - it will be in
940
the most efficient order for the index.
942
if 'evil' in debug.debug_flags:
943
trace.mutter_callsite(3,
944
"iter_all_entries scales with size of history.")
945
if not self.key_count():
947
if self._row_offsets[-1] == 1:
948
# There is only the root node, and we read that via key_count()
949
if self.node_ref_lists:
950
for key, (value, refs) in sorted(self._root_node.keys.items()):
951
yield (self, key, value, refs)
953
for key, (value, refs) in sorted(self._root_node.keys.items()):
954
yield (self, key, value)
956
start_of_leaves = self._row_offsets[-2]
957
end_of_leaves = self._row_offsets[-1]
958
needed_offsets = range(start_of_leaves, end_of_leaves)
959
if needed_offsets == [0]:
960
# Special case when we only have a root node, as we have already
962
nodes = [(0, self._root_node)]
964
nodes = self._read_nodes(needed_offsets)
965
# We iterate strictly in-order so that we can use this function
966
# for spilling index builds to disk.
967
if self.node_ref_lists:
968
for _, node in nodes:
969
for key, (value, refs) in sorted(node.keys.items()):
970
yield (self, key, value, refs)
972
for _, node in nodes:
973
for key, (value, refs) in sorted(node.keys.items()):
974
yield (self, key, value)
977
def _multi_bisect_right(in_keys, fixed_keys):
978
"""Find the positions where each 'in_key' would fit in fixed_keys.
980
This is equivalent to doing "bisect_right" on each in_key into
983
:param in_keys: A sorted list of keys to match with fixed_keys
984
:param fixed_keys: A sorted list of keys to match against
985
:return: A list of (integer position, [key list]) tuples.
990
# no pointers in the fixed_keys list, which means everything must
992
return [(0, in_keys)]
994
# TODO: Iterating both lists will generally take M + N steps
995
# Bisecting each key will generally take M * log2 N steps.
996
# If we had an efficient way to compare, we could pick the method
997
# based on which has the fewer number of steps.
998
# There is also the argument that bisect_right is a compiled
999
# function, so there is even more to be gained.
1000
# iter_steps = len(in_keys) + len(fixed_keys)
1001
# bisect_steps = len(in_keys) * math.log(len(fixed_keys), 2)
1002
if len(in_keys) == 1: # Bisect will always be faster for M = 1
1003
return [(bisect_right(fixed_keys, in_keys[0]), in_keys)]
1004
# elif bisect_steps < iter_steps:
1006
# for key in in_keys:
1007
# offsets.setdefault(bisect_right(fixed_keys, key),
1009
# return [(o, offsets[o]) for o in sorted(offsets)]
1010
in_keys_iter = iter(in_keys)
1011
fixed_keys_iter = enumerate(fixed_keys)
1012
cur_in_key = in_keys_iter.next()
1013
cur_fixed_offset, cur_fixed_key = fixed_keys_iter.next()
1015
class InputDone(Exception): pass
1016
class FixedDone(Exception): pass
1021
# TODO: Another possibility is that rather than iterating on each side,
1022
# we could use a combination of bisecting and iterating. For
1023
# example, while cur_in_key < fixed_key, bisect to find its
1024
# point, then iterate all matching keys, then bisect (restricted
1025
# to only the remainder) for the next one, etc.
1028
if cur_in_key < cur_fixed_key:
1030
cur_out = (cur_fixed_offset, cur_keys)
1031
output.append(cur_out)
1032
while cur_in_key < cur_fixed_key:
1033
cur_keys.append(cur_in_key)
1035
cur_in_key = in_keys_iter.next()
1036
except StopIteration:
1038
# At this point cur_in_key must be >= cur_fixed_key
1039
# step the cur_fixed_key until we pass the cur key, or walk off
1041
while cur_in_key >= cur_fixed_key:
1043
cur_fixed_offset, cur_fixed_key = fixed_keys_iter.next()
1044
except StopIteration:
1047
# We consumed all of the input, nothing more to do
1050
# There was some input left, but we consumed all of fixed, so we
1051
# have to add one more for the tail
1052
cur_keys = [cur_in_key]
1053
cur_keys.extend(in_keys_iter)
1054
cur_out = (len(fixed_keys), cur_keys)
1055
output.append(cur_out)
1058
def _walk_through_internal_nodes(self, keys):
1059
"""Take the given set of keys, and find the corresponding LeafNodes.
1061
:param keys: An unsorted iterable of keys to search for
1062
:return: (nodes, index_and_keys)
1063
nodes is a dict mapping {index: LeafNode}
1064
keys_at_index is a list of tuples of [(index, [keys for Leaf])]
1066
# 6 seconds spent in miss_torture using the sorted() line.
1067
# Even with out of order disk IO it seems faster not to sort it when
1068
# large queries are being made.
1069
keys_at_index = [(0, sorted(keys))]
1071
for row_pos, next_row_start in enumerate(self._row_offsets[1:-1]):
1072
node_indexes = [idx for idx, s_keys in keys_at_index]
1073
nodes = self._get_internal_nodes(node_indexes)
1075
next_nodes_and_keys = []
1076
for node_index, sub_keys in keys_at_index:
1077
node = nodes[node_index]
1078
positions = self._multi_bisect_right(sub_keys, node.keys)
1079
node_offset = next_row_start + node.offset
1080
next_nodes_and_keys.extend([(node_offset + pos, s_keys)
1081
for pos, s_keys in positions])
1082
keys_at_index = next_nodes_and_keys
1083
# We should now be at the _LeafNodes
1084
node_indexes = [idx for idx, s_keys in keys_at_index]
1086
# TODO: We may *not* want to always read all the nodes in one
1087
# big go. Consider setting a max size on this.
1088
nodes = self._get_leaf_nodes(node_indexes)
1089
return nodes, keys_at_index
1091
def iter_entries(self, keys):
1092
"""Iterate over keys within the index.
1094
:param keys: An iterable providing the keys to be retrieved.
1095
:return: An iterable as per iter_all_entries, but restricted to the
1096
keys supplied. No additional keys will be returned, and every
1097
key supplied that is in the index will be returned.
1099
# 6 seconds spent in miss_torture using the sorted() line.
1100
# Even with out of order disk IO it seems faster not to sort it when
1101
# large queries are being made.
1102
# However, now that we are doing multi-way bisecting, we need the keys
1103
# in sorted order anyway. We could change the multi-way code to not
1104
# require sorted order. (For example, it bisects for the first node,
1105
# does an in-order search until a key comes before the current point,
1106
# which it then bisects for, etc.)
1107
keys = frozenset(keys)
1111
if not self.key_count():
1115
if self._leaf_value_cache is None:
1119
value = self._leaf_value_cache.get(key, None)
1120
if value is not None:
1121
# This key is known not to be here, skip it
1123
if self.node_ref_lists:
1124
yield (self, key, value, refs)
1126
yield (self, key, value)
1128
needed_keys.append(key)
1134
nodes, nodes_and_keys = self._walk_through_internal_nodes(needed_keys)
1135
for node_index, sub_keys in nodes_and_keys:
1138
node = nodes[node_index]
1139
for next_sub_key in sub_keys:
1140
if next_sub_key in node.keys:
1141
value, refs = node.keys[next_sub_key]
1142
if self.node_ref_lists:
1143
yield (self, next_sub_key, value, refs)
1145
yield (self, next_sub_key, value)
1147
def _find_ancestors(self, keys, ref_list_num, parent_map, missing_keys):
1148
"""Find the parent_map information for the set of keys.
1150
This populates the parent_map dict and missing_keys set based on the
1151
queried keys. It also can fill out an arbitrary number of parents that
1152
it finds while searching for the supplied keys.
1154
It is unlikely that you want to call this directly. See
1155
"CombinedGraphIndex.find_ancestry()" for a more appropriate API.
1157
:param keys: A keys whose ancestry we want to return
1158
Every key will either end up in 'parent_map' or 'missing_keys'.
1159
:param ref_list_num: This index in the ref_lists is the parents we
1161
:param parent_map: {key: parent_keys} for keys that are present in this
1162
index. This may contain more entries than were in 'keys', that are
1163
reachable ancestors of the keys requested.
1164
:param missing_keys: keys which are known to be missing in this index.
1165
This may include parents that were not directly requested, but we
1166
were able to determine that they are not present in this index.
1167
:return: search_keys parents that were found but not queried to know
1168
if they are missing or present. Callers can re-query this index for
1169
those keys, and they will be placed into parent_map or missing_keys
1171
if not self.key_count():
1172
# We use key_count() to trigger reading the root node and
1173
# determining info about this BTreeGraphIndex
1174
# If we don't have any keys, then everything is missing
1175
missing_keys.update(keys)
1177
if ref_list_num >= self.node_ref_lists:
1178
raise ValueError('No ref list %d, index has %d ref lists'
1179
% (ref_list_num, self.node_ref_lists))
1181
# The main trick we are trying to accomplish is that when we find a
1182
# key listing its parents, we expect that the parent key is also likely
1183
# to sit on the same page. Allowing us to expand parents quickly
1184
# without suffering the full stack of bisecting, etc.
1185
nodes, nodes_and_keys = self._walk_through_internal_nodes(keys)
1187
# These are parent keys which could not be immediately resolved on the
1188
# page where the child was present. Note that we may already be
1189
# searching for that key, and it may actually be present [or known
1190
# missing] on one of the other pages we are reading.
1192
# We could try searching for them in the immediate previous or next
1193
# page. If they occur "later" we could put them in a pending lookup
1194
# set, and then for each node we read thereafter we could check to
1195
# see if they are present.
1196
# However, we don't know the impact of keeping this list of things
1197
# that I'm going to search for every node I come across from here on
1199
# It doesn't handle the case when the parent key is missing on a
1200
# page that we *don't* read. So we already have to handle being
1201
# re-entrant for that.
1202
# Since most keys contain a date string, they are more likely to be
1203
# found earlier in the file than later, but we would know that right
1204
# away (key < min_key), and wouldn't keep searching it on every other
1205
# page that we read.
1206
# Mostly, it is an idea, one which should be benchmarked.
1207
parents_not_on_page = set()
1209
for node_index, sub_keys in nodes_and_keys:
1212
# sub_keys is all of the keys we are looking for that should exist
1213
# on this page, if they aren't here, then they won't be found
1214
node = nodes[node_index]
1215
node_keys = node.keys
1216
parents_to_check = set()
1217
for next_sub_key in sub_keys:
1218
if next_sub_key not in node_keys:
1219
# This one is just not present in the index at all
1220
missing_keys.add(next_sub_key)
1222
value, refs = node_keys[next_sub_key]
1223
parent_keys = refs[ref_list_num]
1224
parent_map[next_sub_key] = parent_keys
1225
parents_to_check.update(parent_keys)
1226
# Don't look for things we've already found
1227
parents_to_check = parents_to_check.difference(parent_map)
1228
# this can be used to test the benefit of having the check loop
1230
# parents_not_on_page.update(parents_to_check)
1232
while parents_to_check:
1233
next_parents_to_check = set()
1234
for key in parents_to_check:
1235
if key in node_keys:
1236
value, refs = node_keys[key]
1237
parent_keys = refs[ref_list_num]
1238
parent_map[key] = parent_keys
1239
next_parents_to_check.update(parent_keys)
1241
# This parent either is genuinely missing, or should be
1242
# found on another page. Perf test whether it is better
1243
# to check if this node should fit on this page or not.
1244
# in the 'everything-in-one-pack' scenario, this *not*
1245
# doing the check is 237ms vs 243ms.
1246
# So slightly better, but I assume the standard 'lots
1247
# of packs' is going to show a reasonable improvement
1248
# from the check, because it avoids 'going around
1249
# again' for everything that is in another index
1250
# parents_not_on_page.add(key)
1251
# Missing for some reason
1252
if key < node.min_key:
1253
# in the case of bzr.dev, 3.4k/5.3k misses are
1254
# 'earlier' misses (65%)
1255
parents_not_on_page.add(key)
1256
elif key > node.max_key:
1257
# This parent key would be present on a different
1259
parents_not_on_page.add(key)
1261
# assert key != node.min_key and key != node.max_key
1262
# If it was going to be present, it would be on
1263
# *this* page, so mark it missing.
1264
missing_keys.add(key)
1265
parents_to_check = next_parents_to_check.difference(parent_map)
1266
# Might want to do another .difference() from missing_keys
1267
# parents_not_on_page could have been found on a different page, or be
1268
# known to be missing. So cull out everything that has already been
1270
search_keys = parents_not_on_page.difference(
1271
parent_map).difference(missing_keys)
1274
def iter_entries_prefix(self, keys):
1275
"""Iterate over keys within the index using prefix matching.
1277
Prefix matching is applied within the tuple of a key, not to within
1278
the bytestring of each key element. e.g. if you have the keys ('foo',
1279
'bar'), ('foobar', 'gam') and do a prefix search for ('foo', None) then
1280
only the former key is returned.
1282
WARNING: Note that this method currently causes a full index parse
1283
unconditionally (which is reasonably appropriate as it is a means for
1284
thunking many small indices into one larger one and still supplies
1285
iter_all_entries at the thunk layer).
1287
:param keys: An iterable providing the key prefixes to be retrieved.
1288
Each key prefix takes the form of a tuple the length of a key, but
1289
with the last N elements 'None' rather than a regular bytestring.
1290
The first element cannot be 'None'.
1291
:return: An iterable as per iter_all_entries, but restricted to the
1292
keys with a matching prefix to those supplied. No additional keys
1293
will be returned, and every match that is in the index will be
1296
keys = sorted(set(keys))
1299
# Load if needed to check key lengths
1300
if self._key_count is None:
1301
self._get_root_node()
1302
# TODO: only access nodes that can satisfy the prefixes we are looking
1303
# for. For now, to meet API usage (as this function is not used by
1304
# current bzrlib) just suck the entire index and iterate in memory.
1306
if self.node_ref_lists:
1307
if self._key_length == 1:
1308
for _1, key, value, refs in self.iter_all_entries():
1309
nodes[key] = value, refs
1312
for _1, key, value, refs in self.iter_all_entries():
1313
key_value = key, value, refs
1314
# For a key of (foo, bar, baz) create
1315
# _nodes_by_key[foo][bar][baz] = key_value
1316
key_dict = nodes_by_key
1317
for subkey in key[:-1]:
1318
key_dict = key_dict.setdefault(subkey, {})
1319
key_dict[key[-1]] = key_value
1321
if self._key_length == 1:
1322
for _1, key, value in self.iter_all_entries():
1326
for _1, key, value in self.iter_all_entries():
1327
key_value = key, value
1328
# For a key of (foo, bar, baz) create
1329
# _nodes_by_key[foo][bar][baz] = key_value
1330
key_dict = nodes_by_key
1331
for subkey in key[:-1]:
1332
key_dict = key_dict.setdefault(subkey, {})
1333
key_dict[key[-1]] = key_value
1334
if self._key_length == 1:
1338
raise errors.BadIndexKey(key)
1339
if len(key) != self._key_length:
1340
raise errors.BadIndexKey(key)
1342
if self.node_ref_lists:
1343
value, node_refs = nodes[key]
1344
yield self, key, value, node_refs
1346
yield self, key, nodes[key]
1353
raise errors.BadIndexKey(key)
1354
if len(key) != self._key_length:
1355
raise errors.BadIndexKey(key)
1356
# find what it refers to:
1357
key_dict = nodes_by_key
1358
elements = list(key)
1359
# find the subdict whose contents should be returned.
1361
while len(elements) and elements[0] is not None:
1362
key_dict = key_dict[elements[0]]
1365
# a non-existant lookup.
1370
key_dict = dicts.pop(-1)
1371
# can't be empty or would not exist
1372
item, value = key_dict.iteritems().next()
1373
if type(value) == dict:
1375
dicts.extend(key_dict.itervalues())
1378
for value in key_dict.itervalues():
1379
# each value is the key:value:node refs tuple
1381
yield (self, ) + value
1383
# the last thing looked up was a terminal element
1384
yield (self, ) + key_dict
1386
def key_count(self):
1387
"""Return an estimate of the number of keys in this index.
1389
For BTreeGraphIndex the estimate is exact as it is contained in the
1392
if self._key_count is None:
1393
self._get_root_node()
1394
return self._key_count
1396
def _compute_row_offsets(self):
1397
"""Fill out the _row_offsets attribute based on _row_lengths."""
1400
for row in self._row_lengths:
1401
offsets.append(row_offset)
1403
offsets.append(row_offset)
1404
self._row_offsets = offsets
1406
def _parse_header_from_bytes(self, bytes):
1407
"""Parse the header from a region of bytes.
1409
:param bytes: The data to parse.
1410
:return: An offset, data tuple such as readv yields, for the unparsed
1411
data. (which may be of length 0).
1413
signature = bytes[0:len(self._signature())]
1414
if not signature == self._signature():
1415
raise errors.BadIndexFormatSignature(self._name, BTreeGraphIndex)
1416
lines = bytes[len(self._signature()):].splitlines()
1417
options_line = lines[0]
1418
if not options_line.startswith(_OPTION_NODE_REFS):
1419
raise errors.BadIndexOptions(self)
1421
self.node_ref_lists = int(options_line[len(_OPTION_NODE_REFS):])
1423
raise errors.BadIndexOptions(self)
1424
options_line = lines[1]
1425
if not options_line.startswith(_OPTION_KEY_ELEMENTS):
1426
raise errors.BadIndexOptions(self)
1428
self._key_length = int(options_line[len(_OPTION_KEY_ELEMENTS):])
1430
raise errors.BadIndexOptions(self)
1431
options_line = lines[2]
1432
if not options_line.startswith(_OPTION_LEN):
1433
raise errors.BadIndexOptions(self)
1435
self._key_count = int(options_line[len(_OPTION_LEN):])
1437
raise errors.BadIndexOptions(self)
1438
options_line = lines[3]
1439
if not options_line.startswith(_OPTION_ROW_LENGTHS):
1440
raise errors.BadIndexOptions(self)
1442
self._row_lengths = map(int, [length for length in
1443
options_line[len(_OPTION_ROW_LENGTHS):].split(',')
1446
raise errors.BadIndexOptions(self)
1447
self._compute_row_offsets()
1449
# calculate the bytes we have processed
1450
header_end = (len(signature) + sum(map(len, lines[0:4])) + 4)
1451
return header_end, bytes[header_end:]
1453
def _read_nodes(self, nodes):
1454
"""Read some nodes from disk into the LRU cache.
1456
This performs a readv to get the node data into memory, and parses each
1457
node, then yields it to the caller. The nodes are requested in the
1458
supplied order. If possible doing sort() on the list before requesting
1459
a read may improve performance.
1461
:param nodes: The nodes to read. 0 - first node, 1 - second node etc.
1464
# may be the byte string of the whole file
1466
# list of (offset, length) regions of the file that should, evenually
1467
# be read in to data_ranges, either from 'bytes' or from the transport
1470
offset = index * _PAGE_SIZE
1473
# Root node - special case
1475
size = min(_PAGE_SIZE, self._size)
1477
# The only case where we don't know the size, is for very
1478
# small indexes. So we read the whole thing
1479
bytes = self._transport.get_bytes(self._name)
1480
self._size = len(bytes)
1481
# the whole thing should be parsed out of 'bytes'
1482
ranges.append((0, len(bytes)))
1485
if offset > self._size:
1486
raise AssertionError('tried to read past the end'
1487
' of the file %s > %s'
1488
% (offset, self._size))
1489
size = min(size, self._size - offset)
1490
ranges.append((offset, size))
1493
elif bytes is not None:
1494
# already have the whole file
1495
data_ranges = [(start, bytes[start:start+_PAGE_SIZE])
1496
for start in xrange(0, len(bytes), _PAGE_SIZE)]
1497
elif self._file is None:
1498
data_ranges = self._transport.readv(self._name, ranges)
1501
for offset, size in ranges:
1502
self._file.seek(offset)
1503
data_ranges.append((offset, self._file.read(size)))
1504
for offset, data in data_ranges:
1506
# extract the header
1507
offset, data = self._parse_header_from_bytes(data)
1510
bytes = zlib.decompress(data)
1511
if bytes.startswith(_LEAF_FLAG):
1512
node = _LeafNode(bytes, self._key_length, self.node_ref_lists)
1513
elif bytes.startswith(_INTERNAL_FLAG):
1514
node = _InternalNode(bytes)
1516
raise AssertionError("Unknown node type for %r" % bytes)
1517
yield offset / _PAGE_SIZE, node
1519
def _signature(self):
1520
"""The file signature for this index type."""
1524
"""Validate that everything in the index can be accessed."""
1525
# just read and parse every node.
1526
self._get_root_node()
1527
if len(self._row_lengths) > 1:
1528
start_node = self._row_offsets[1]
1530
# We shouldn't be reading anything anyway
1532
node_end = self._row_offsets[-1]
1533
for node in self._read_nodes(range(start_node, node_end)):
1538
from bzrlib import _btree_serializer_pyx as _btree_serializer
1539
except ImportError, e:
1540
osutils.failed_to_load_extension(e)
1541
from bzrlib import _btree_serializer_py as _btree_serializer
added
removed
bzrlib/btree_index.py
