Mercurial > hg
view mercurial/metadata.py @ 51795:73476a9e5ced stable
histedit: create state and acquire locks earlier
This makes chistedit (histedit with curses UI) not write any files inside repo
without wlock. It also makes sense to wrap the entire process of preparing
commands inside the curses UI inside locks because we don't want anything else
to touch wdir or repo during this time.
| author | Anton Shestakov <av6@dwimlabs.net> |
|---|---|
| date | Thu, 08 Aug 2024 17:28:38 +0400 |
| parents | 7d9bd50afe3d |
| children | 454feddab720 |
line wrap: on
line source
# coding: utf-8 # metadata.py -- code related to various metadata computation and access. # # Copyright 2019 Google, Inc <martinvonz@google.com> # Copyright 2020 Pierre-Yves David <pierre-yves.david@octobus.net> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. import multiprocessing import struct from .node import nullrev from . import ( error, util, ) from .revlogutils import ( flagutil as sidedataflag, sidedata as sidedatamod, ) class ChangingFiles: """A class recording the changes made to files by a changeset Actions performed on files are gathered into 3 sets: - added: files actively added in the changeset. - merged: files whose history got merged - removed: files removed in the revision - salvaged: files that might have been deleted by a merge but were not - touched: files affected by the merge and copies information is held by 2 mappings - copied_from_p1: {"<new-name>": "<source-name-in-p1>"} mapping for copies - copied_from_p2: {"<new-name>": "<source-name-in-p2>"} mapping for copies See their inline help for details. """ def __init__( self, touched=None, added=None, removed=None, merged=None, salvaged=None, p1_copies=None, p2_copies=None, ): self._added = set(() if added is None else added) self._merged = set(() if merged is None else merged) self._removed = set(() if removed is None else removed) self._touched = set(() if touched is None else touched) self._salvaged = set(() if salvaged is None else salvaged) self._touched.update(self._added) self._touched.update(self._merged) self._touched.update(self._removed) self._p1_copies = dict(() if p1_copies is None else p1_copies) self._p2_copies = dict(() if p2_copies is None else p2_copies) def __eq__(self, other): return ( self.added == other.added and self.merged == other.merged and self.removed == other.removed and self.salvaged == other.salvaged and self.touched == other.touched and self.copied_from_p1 == other.copied_from_p1 and self.copied_from_p2 == other.copied_from_p2 ) @property def has_copies_info(self): return bool( self.removed or self.merged or self.salvaged or self.copied_from_p1 or self.copied_from_p2 ) @util.propertycache def added(self): """files actively added in the changeset Any file present in that revision that was absent in all the changeset's parents. In case of merge, this means a file absent in one of the parents but existing in the other will *not* be contained in this set. (They were added by an ancestor) """ return frozenset(self._added) def mark_added(self, filename): if 'added' in vars(self): del self.added self._added.add(filename) self.mark_touched(filename) def update_added(self, filenames): for f in filenames: self.mark_added(f) @util.propertycache def merged(self): """files actively merged during a merge Any modified files which had modification on both size that needed merging. In this case a new filenode was created and it has two parents. """ return frozenset(self._merged) def mark_merged(self, filename): if 'merged' in vars(self): del self.merged self._merged.add(filename) self.mark_touched(filename) def update_merged(self, filenames): for f in filenames: self.mark_merged(f) @util.propertycache def removed(self): """files actively removed by the changeset In case of merge this will only contain the set of files removing "new" content. For any file absent in the current changeset: a) If the file exists in both parents, it is clearly "actively" removed by this changeset. b) If a file exists in only one parent and in none of the common ancestors, then the file was newly added in one of the merged branches and then got "actively" removed. c) If a file exists in only one parent and at least one of the common ancestors using the same filenode, then the file was unchanged on one side and deleted on the other side. The merge "passively" propagated that deletion, but didn't "actively" remove the file. In this case the file is *not* included in the `removed` set. d) If a file exists in only one parent and at least one of the common ancestors using a different filenode, then the file was changed on one side and removed on the other side. The merge process "actively" decided to drop the new change and delete the file. Unlike in the previous case, (c), the file included in the `removed` set. Summary table for merge: case | exists in parents | exists in gca || removed (a) | both | * || yes (b) | one | none || yes (c) | one | same filenode || no (d) | one | new filenode || yes """ return frozenset(self._removed) def mark_removed(self, filename): if 'removed' in vars(self): del self.removed self._removed.add(filename) self.mark_touched(filename) def update_removed(self, filenames): for f in filenames: self.mark_removed(f) @util.propertycache def salvaged(self): """files that might have been deleted by a merge, but still exists. During a merge, the manifest merging might select some files for removal, or for a removed/changed conflict. If at commit time the file still exists, its removal was "reverted" and the file is "salvaged" """ return frozenset(self._salvaged) def mark_salvaged(self, filename): if "salvaged" in vars(self): del self.salvaged self._salvaged.add(filename) self.mark_touched(filename) def update_salvaged(self, filenames): for f in filenames: self.mark_salvaged(f) @util.propertycache def touched(self): """files either actively modified, added or removed""" return frozenset(self._touched) def mark_touched(self, filename): if 'touched' in vars(self): del self.touched self._touched.add(filename) def update_touched(self, filenames): for f in filenames: self.mark_touched(f) @util.propertycache def copied_from_p1(self): return self._p1_copies.copy() def mark_copied_from_p1(self, source, dest): if 'copied_from_p1' in vars(self): del self.copied_from_p1 self._p1_copies[dest] = source def update_copies_from_p1(self, copies): for dest, source in copies.items(): self.mark_copied_from_p1(source, dest) @util.propertycache def copied_from_p2(self): return self._p2_copies.copy() def mark_copied_from_p2(self, source, dest): if 'copied_from_p2' in vars(self): del self.copied_from_p2 self._p2_copies[dest] = source def update_copies_from_p2(self, copies): for dest, source in copies.items(): self.mark_copied_from_p2(source, dest) def compute_all_files_changes(ctx): """compute the files changed by a revision""" p1 = ctx.p1() p2 = ctx.p2() if p1.rev() == nullrev and p2.rev() == nullrev: return _process_root(ctx) elif p1.rev() != nullrev and p2.rev() == nullrev: return _process_linear(p1, ctx) elif p1.rev() == nullrev and p2.rev() != nullrev: # In the wild, one can encounter changeset where p1 is null but p2 is not return _process_linear(p2, ctx, parent=2) elif p1.rev() == p2.rev(): # In the wild, one can encounter such "non-merge" return _process_linear(p1, ctx) else: return _process_merge(p1, p2, ctx) def _process_root(ctx): """compute the appropriate changed files for a changeset with no parents""" # Simple, there was nothing before it, so everything is added. md = ChangingFiles() manifest = ctx.manifest() for filename in manifest: md.mark_added(filename) return md def _process_linear(parent_ctx, children_ctx, parent=1): """compute the appropriate changed files for a changeset with a single parent""" md = ChangingFiles() parent_manifest = parent_ctx.manifest() children_manifest = children_ctx.manifest() copies_candidate = [] for filename, d in parent_manifest.diff(children_manifest).items(): if d[1][0] is None: # no filenode for the "new" value, file is absent md.mark_removed(filename) else: copies_candidate.append(filename) if d[0][0] is None: # not filenode for the "old" value file was absent md.mark_added(filename) else: # filenode for both "old" and "new" md.mark_touched(filename) if parent == 1: copied = md.mark_copied_from_p1 elif parent == 2: copied = md.mark_copied_from_p2 else: assert False, "bad parent value %d" % parent for filename in copies_candidate: copy_info = children_ctx[filename].renamed() if copy_info: source, srcnode = copy_info copied(source, filename) return md def _process_merge(p1_ctx, p2_ctx, ctx): """compute the appropriate changed files for a changeset with two parents This is a more advance case. The information we need to record is summarise in the following table: ┌──────────────┬──────────────┬──────────────┬──────────────┬──────────────┐ │ diff ╲ diff │ ø │ (Some, None) │ (None, Some) │ (Some, Some) │ │ p2 ╲ p1 │ │ │ │ │ ├──────────────┼──────────────┼──────────────┼──────────────┼──────────────┤ │ │ │🄱 No Changes │🄳 No Changes │ │ │ ø │🄰 No Changes │ OR │ OR │🄵 No Changes │ │ │ │🄲 Deleted[1] │🄴 Salvaged[2]│ [3] │ ├──────────────┼──────────────┼──────────────┼──────────────┼──────────────┤ │ │🄶 No Changes │ │ │ │ │ (Some, None) │ OR │🄻 Deleted │ ø │ ø │ │ │🄷 Deleted[1] │ │ │ │ ├──────────────┼──────────────┼──────────────┼──────────────┼──────────────┤ │ │🄸 No Changes │ │ │ 🄽 Touched │ │ (None, Some) │ OR │ ø │🄼 Added │OR 🅀 Salvaged │ │ │🄹 Salvaged[2]│ │ (copied?) │ (copied?) │ ├──────────────┼──────────────┼──────────────┼──────────────┼──────────────┤ │ │ │ │ 🄾 Touched │ 🄿 Merged │ │ (Some, Some) │🄺 No Changes │ ø │OR 🅁 Salvaged │OR 🅂 Touched │ │ │ [3] │ │ (copied?) │ (copied?) │ └──────────────┴──────────────┴──────────────┴──────────────┴──────────────┘ Special case [1]: The situation is: - parent-A: file exists, - parent-B: no file, - working-copy: no file. Detecting a "deletion" will depend on the presence of actual change on the "parent-A" branch: Subcase 🄱 or 🄶 : if the state of the file in "parent-A" is unchanged compared to the merge ancestors, then parent-A branch left the file untouched while parent-B deleted it. We simply apply the change from "parent-B" branch the file was automatically dropped. The result is: - file is not recorded as touched by the merge. Subcase 🄲 or 🄷 : otherwise, the change from parent-A branch were explicitly dropped and the file was "deleted again". From a user perspective, the message about "locally changed" while "remotely deleted" (or the other way around) was issued and the user chose to deleted the file. The result: - file is recorded as touched by the merge. Special case [2]: The situation is: - parent-A: no file, - parent-B: file, - working-copy: file (same content as parent-B). There are three subcases depending on the ancestors contents: - A) the file is missing in all ancestors, - B) at least one ancestor has the file with filenode ≠ from parent-B, - C) all ancestors use the same filenode as parent-B, Subcase (A) is the simpler, nothing happend on parent-A side while parent-B added it. The result: - the file is not marked as touched by the merge. Subcase (B) is the counter part of "Special case [1]", the file was modified on parent-B side, while parent-A side deleted it. However this time, the conflict was solved by keeping the file (and its modification). We consider the file as "salvaged". The result: - the file is marked as "salvaged" by the merge. Subcase (C) is subtle variation of the case above. In this case, the file in unchanged on the parent-B side and actively removed on the parent-A side. So the merge machinery correctly decide it should be removed. However, the file was explicitly restored to its parent-B content before the merge was commited. The file is be marked as salvaged too. From the merge result perspective, this is similar to Subcase (B), however from the merge resolution perspective they differ since in (C), there was some conflict not obvious solution to the merge (That got reversed) Special case [3]: The situation is: - parent-A: file, - parent-B: file (different filenode as parent-A), - working-copy: file (same filenode as parent-B). This case is in theory much simple, for this to happens, this mean the filenode in parent-A is purely replacing the one in parent-B (either a descendant, or a full new file history, see changeset). So the merge introduce no changes, and the file is not affected by the merge... However, in the wild it is possible to find commit with the above is not True. For example repository have some commit where the *new* node is an ancestor of the node in parent-A, or where parent-A and parent-B are two branches of the same file history, yet not merge-filenode were created (while the "merge" should have led to a "modification"). Detecting such cases (and not recording the file as modified) would be a nice bonus. However do not any of this yet. """ repo = ctx.repo() md = ChangingFiles() m = ctx.manifest() p1m = p1_ctx.manifest() p2m = p2_ctx.manifest() diff_p1 = p1m.diff(m) diff_p2 = p2m.diff(m) cahs = ctx.repo().changelog.commonancestorsheads( p1_ctx.node(), p2_ctx.node() ) if not cahs: cahs = [nullrev] mas = [ctx.repo()[r].manifest() for r in cahs] copy_candidates = [] # Dealing with case 🄰 happens automatically. Since there are no entry in # d1 nor d2, we won't iterate on it ever. # Iteration over d1 content will deal with all cases, but the one in the # first column of the table. for filename, d1 in diff_p1.items(): d2 = diff_p2.pop(filename, None) if d2 is None: # this deal with the first line of the table. _process_other_unchanged(md, mas, filename, d1) else: if d1[0][0] is None and d2[0][0] is None: # case 🄼 — both deleted the file. md.mark_added(filename) copy_candidates.append(filename) elif d1[1][0] is None and d2[1][0] is None: # case 🄻 — both deleted the file. md.mark_removed(filename) elif d1[1][0] is not None and d2[1][0] is not None: if d1[0][0] is None or d2[0][0] is None: if any(_find(ma, filename) is not None for ma in mas): # case 🅀 or 🅁 md.mark_salvaged(filename) else: # case 🄽 🄾 : touched md.mark_touched(filename) else: fctx = repo.filectx(filename, fileid=d1[1][0]) if fctx.p2().rev() == nullrev: # case 🅂 # lets assume we can trust the file history. If the # filenode is not a merge, the file was not merged. md.mark_touched(filename) else: # case 🄿 md.mark_merged(filename) copy_candidates.append(filename) else: # Impossible case, the post-merge file status cannot be None on # one side and Something on the other side. assert False, "unreachable" # Iteration over remaining d2 content deal with the first column of the # table. for filename, d2 in diff_p2.items(): _process_other_unchanged(md, mas, filename, d2) for filename in copy_candidates: copy_info = ctx[filename].renamed() if copy_info: source, srcnode = copy_info if source in p1_ctx and p1_ctx[source].filenode() == srcnode: md.mark_copied_from_p1(source, filename) elif source in p2_ctx and p2_ctx[source].filenode() == srcnode: md.mark_copied_from_p2(source, filename) return md def _find(manifest, filename): """return the associate filenode or None""" if filename not in manifest: return None return manifest.find(filename)[0] def _process_other_unchanged(md, mas, filename, diff): source_node = diff[0][0] target_node = diff[1][0] if source_node is not None and target_node is None: if any(not _find(ma, filename) == source_node for ma in mas): # case 🄲 of 🄷 md.mark_removed(filename) # else, we have case 🄱 or 🄶 : no change need to be recorded elif source_node is None and target_node is not None: if any(_find(ma, filename) is not None for ma in mas): # case 🄴 or 🄹 md.mark_salvaged(filename) # else, we have case 🄳 or 🄸 : simple merge without intervention elif source_node is not None and target_node is not None: # case 🄵 or 🄺 : simple merge without intervention # # In buggy case where source_node is not an ancestors of target_node. # There should have a been a new filenode created, recording this as # "modified". We do not deal with them yet. pass else: # An impossible case, the diff algorithm should not return entry if the # file is missing on both side. assert False, "unreachable" def _missing_from_all_ancestors(mas, filename): return all(_find(ma, filename) is None for ma in mas) def computechangesetfilesadded(ctx): """return the list of files added in a changeset""" added = [] for f in ctx.files(): if not any(f in p for p in ctx.parents()): added.append(f) return added def get_removal_filter(ctx, x=None): """return a function to detect files "wrongly" detected as `removed` When a file is removed relative to p1 in a merge, this function determines whether the absence is due to a deletion from a parent, or whether the merge commit itself deletes the file. We decide this by doing a simplified three way merge of the manifest entry for the file. There are two ways we decide the merge itself didn't delete a file: - neither parent (nor the merge) contain the file - exactly one parent contains the file, and that parent has the same filelog entry as the merge ancestor (or all of them if there two). In other words, that parent left the file unchanged while the other one deleted it. One way to think about this is that deleting a file is similar to emptying it, so the list of changed files should be similar either way. The computation described above is not done directly in _filecommit when creating the list of changed files, however it does something very similar by comparing filelog nodes. """ if x is not None: p1, p2, m1, m2 = x else: p1 = ctx.p1() p2 = ctx.p2() m1 = p1.manifest() m2 = p2.manifest() @util.cachefunc def mas(): p1n = p1.node() p2n = p2.node() cahs = ctx.repo().changelog.commonancestorsheads(p1n, p2n) if not cahs: cahs = [nullrev] return [ctx.repo()[r].manifest() for r in cahs] def deletionfromparent(f): if f in m1: return f not in m2 and all( f in ma and ma.find(f) == m1.find(f) for ma in mas() ) elif f in m2: return all(f in ma and ma.find(f) == m2.find(f) for ma in mas()) else: return True return deletionfromparent def computechangesetfilesremoved(ctx): """return the list of files removed in a changeset""" removed = [] for f in ctx.files(): if f not in ctx: removed.append(f) if removed: rf = get_removal_filter(ctx) removed = [r for r in removed if not rf(r)] return removed def computechangesetfilesmerged(ctx): """return the list of files merged in a changeset""" merged = [] if len(ctx.parents()) < 2: return merged for f in ctx.files(): if f in ctx: fctx = ctx[f] parents = fctx._filelog.parents(fctx._filenode) if parents[1] != ctx.repo().nullid: merged.append(f) return merged def computechangesetcopies(ctx): """return the copies data for a changeset The copies data are returned as a pair of dictionnary (p1copies, p2copies). Each dictionnary are in the form: `{newname: oldname}` """ p1copies = {} p2copies = {} p1 = ctx.p1() p2 = ctx.p2() narrowmatch = ctx._repo.narrowmatch() for dst in ctx.files(): if not narrowmatch(dst) or dst not in ctx: continue copied = ctx[dst].renamed() if not copied: continue src, srcnode = copied if src in p1 and p1[src].filenode() == srcnode: p1copies[dst] = src elif src in p2 and p2[src].filenode() == srcnode: p2copies[dst] = src return p1copies, p2copies def encodecopies(files, copies): items = [] for i, dst in enumerate(files): if dst in copies: items.append(b'%d\0%s' % (i, copies[dst])) if len(items) != len(copies): raise error.ProgrammingError( b'some copy targets missing from file list' ) return b"\n".join(items) def decodecopies(files, data): try: copies = {} if not data: return copies for l in data.split(b'\n'): strindex, src = l.split(b'\0') i = int(strindex) dst = files[i] copies[dst] = src return copies except (ValueError, IndexError): # Perhaps someone had chosen the same key name (e.g. "p1copies") and # used different syntax for the value. return None def encodefileindices(files, subset): subset = set(subset) indices = [] for i, f in enumerate(files): if f in subset: indices.append(b'%d' % i) return b'\n'.join(indices) def decodefileindices(files, data): try: subset = [] if not data: return subset for strindex in data.split(b'\n'): i = int(strindex) if i < 0 or i >= len(files): return None subset.append(files[i]) return subset except (ValueError, IndexError): # Perhaps someone had chosen the same key name (e.g. "added") and # used different syntax for the value. return None # see mercurial/helptext/internals/revlogs.txt for details about the format ACTION_MASK = int("111" "00", 2) # note: untouched file used as copy source will as `000` for this mask. ADDED_FLAG = int("001" "00", 2) MERGED_FLAG = int("010" "00", 2) REMOVED_FLAG = int("011" "00", 2) SALVAGED_FLAG = int("100" "00", 2) TOUCHED_FLAG = int("101" "00", 2) COPIED_MASK = int("11", 2) COPIED_FROM_P1_FLAG = int("10", 2) COPIED_FROM_P2_FLAG = int("11", 2) # structure is <flag><filename-end><copy-source> INDEX_HEADER = struct.Struct(">L") INDEX_ENTRY = struct.Struct(">bLL") def encode_files_sidedata(files): all_files = set(files.touched) all_files.update(files.copied_from_p1.values()) all_files.update(files.copied_from_p2.values()) all_files = sorted(all_files) file_idx = {f: i for (i, f) in enumerate(all_files)} file_idx[None] = 0 chunks = [INDEX_HEADER.pack(len(all_files))] filename_length = 0 for f in all_files: filename_size = len(f) filename_length += filename_size flag = 0 if f in files.added: flag |= ADDED_FLAG elif f in files.merged: flag |= MERGED_FLAG elif f in files.removed: flag |= REMOVED_FLAG elif f in files.salvaged: flag |= SALVAGED_FLAG elif f in files.touched: flag |= TOUCHED_FLAG copy = None if f in files.copied_from_p1: flag |= COPIED_FROM_P1_FLAG copy = files.copied_from_p1.get(f) elif f in files.copied_from_p2: copy = files.copied_from_p2.get(f) flag |= COPIED_FROM_P2_FLAG copy_idx = file_idx[copy] chunks.append(INDEX_ENTRY.pack(flag, filename_length, copy_idx)) chunks.extend(all_files) return {sidedatamod.SD_FILES: b''.join(chunks)} def decode_files_sidedata(sidedata): md = ChangingFiles() raw = sidedata.get(sidedatamod.SD_FILES) if raw is None: return md copies = [] all_files = [] assert len(raw) >= INDEX_HEADER.size total_files = INDEX_HEADER.unpack_from(raw, 0)[0] offset = INDEX_HEADER.size file_offset_base = offset + (INDEX_ENTRY.size * total_files) file_offset_last = file_offset_base assert len(raw) >= file_offset_base for idx in range(total_files): flag, file_end, copy_idx = INDEX_ENTRY.unpack_from(raw, offset) file_end += file_offset_base filename = raw[file_offset_last:file_end] filesize = file_end - file_offset_last assert len(filename) == filesize offset += INDEX_ENTRY.size file_offset_last = file_end all_files.append(filename) if flag & ACTION_MASK == ADDED_FLAG: md.mark_added(filename) elif flag & ACTION_MASK == MERGED_FLAG: md.mark_merged(filename) elif flag & ACTION_MASK == REMOVED_FLAG: md.mark_removed(filename) elif flag & ACTION_MASK == SALVAGED_FLAG: md.mark_salvaged(filename) elif flag & ACTION_MASK == TOUCHED_FLAG: md.mark_touched(filename) copied = None if flag & COPIED_MASK == COPIED_FROM_P1_FLAG: copied = md.mark_copied_from_p1 elif flag & COPIED_MASK == COPIED_FROM_P2_FLAG: copied = md.mark_copied_from_p2 if copied is not None: copies.append((copied, filename, copy_idx)) for copied, filename, copy_idx in copies: copied(all_files[copy_idx], filename) return md def _getsidedata(srcrepo, rev): ctx = srcrepo[rev] files = compute_all_files_changes(ctx) return encode_files_sidedata(files), files.has_copies_info def copies_sidedata_computer(repo, revlog, rev, existing_sidedata): sidedata, has_copies_info = _getsidedata(repo, rev) flags_to_add = sidedataflag.REVIDX_HASCOPIESINFO if has_copies_info else 0 return sidedata, (flags_to_add, 0) def _sidedata_worker(srcrepo, revs_queue, sidedata_queue, tokens): """The function used by worker precomputing sidedata It read an input queue containing revision numbers It write in an output queue containing (rev, <sidedata-map>) The `None` input value is used as a stop signal. The `tokens` semaphore is user to avoid having too many unprocessed entries. The workers needs to acquire one token before fetching a task. They will be released by the consumer of the produced data. """ tokens.acquire() rev = revs_queue.get() while rev is not None: data = _getsidedata(srcrepo, rev) sidedata_queue.put((rev, data)) tokens.acquire() rev = revs_queue.get() # processing of `None` is completed, release the token. tokens.release() BUFF_PER_WORKER = 50 def _get_worker_sidedata_adder(srcrepo, destrepo): """The parallel version of the sidedata computation This code spawn a pool of worker that precompute a buffer of sidedata before we actually need them""" # avoid circular import copies -> scmutil -> worker -> copies from . import worker nbworkers = worker._numworkers(srcrepo.ui) tokens = multiprocessing.BoundedSemaphore(nbworkers * BUFF_PER_WORKER) revsq = multiprocessing.Queue() sidedataq = multiprocessing.Queue() assert srcrepo.filtername is None # queue all tasks beforehand, revision numbers are small and it make # synchronisation simpler # # Since the computation for each node can be quite expensive, the overhead # of using a single queue is not revelant. In practice, most computation # are fast but some are very expensive and dominate all the other smaller # cost. for r in srcrepo.changelog.revs(): revsq.put(r) # queue the "no more tasks" markers for i in range(nbworkers): revsq.put(None) allworkers = [] for i in range(nbworkers): args = (srcrepo, revsq, sidedataq, tokens) w = multiprocessing.Process(target=_sidedata_worker, args=args) allworkers.append(w) w.start() # dictionnary to store results for revision higher than we one we are # looking for. For example, if we need the sidedatamap for 42, and 43 is # received, when shelve 43 for later use. staging = {} def sidedata_companion(repo, revlog, rev, old_sidedata): # Is the data previously shelved ? data = staging.pop(rev, None) if data is None: # look at the queued result until we find the one we are lookig # for (shelve the other ones) r, data = sidedataq.get() while r != rev: staging[r] = data r, data = sidedataq.get() tokens.release() sidedata, has_copies_info = data new_flag = 0 if has_copies_info: new_flag = sidedataflag.REVIDX_HASCOPIESINFO return sidedata, (new_flag, 0) return sidedata_companion