Mercurial > hg
view mercurial/tags.py @ 29375:fcaf20175b1b
demandimport: delay loading for "from a import b" with absolute_import
Before this patch, "from a import b" doesn't delay loading module "b",
if absolute_import is enabled, even though "from . import b" does.
For example:
- it is assumed that extension X has "from P import M" for module M
under package P with absolute_import feature
- if importing module M is already delayed before loading extension
X, loading module M in extension X is delayed until actually
referring
util, cmdutil, scmutil or so of Mercurial itself should be
imported by "from . import M" style before loading extension X
- otherwise, module M is loaded immediately at loading extension X,
even if extension X itself isn't used at that "hg" command invocation
Some minor modules (e.g. filemerge or so) of Mercurial itself
aren't imported by "from . import M" style before loading
extension X. And of course, external libraries aren't, too.
This might cause startup performance problem of hg command, because
many bundled extensions already enable absolute_import feature.
To delay loading module for "from a import b" with absolute_import
feature, this patch does below in "from a (or .a) import b" with
absolute_import case:
1. import root module of "name" by system built-in __import__
(referred as _origimport)
2. recurse down the module chain for hierarchical "name"
This logic can be shared with non absolute_import
case. Therefore, this patch also centralizes it into chainmodules().
3. and fall through to process elements in "fromlist" for the leaf
module of "name"
Processing elements in "fromlist" is executed in the code path
after "if _pypy: .... else: ..." clause. Therefore, this patch
replaces "if _pypy:" with "elif _pypy:" to share it.
At 4f1144c3c72b introducing original "work around" for "from a import
b" case, elements in "fromlist" were imported with "level=level". But
"level" might be grater than 1 (e.g. level=2 in "from .. import b"
case) at demandimport() invocation, and importing direct sub-module in
"fromlist" with level grater than 1 causes unexpected result.
IMHO, this seems main reason of "errors for unknown reason" described
in 4f1144c3c72b, and we don't have to worry about it, because this
issue was already fixed by 78d05778907b.
This is reason why this patch removes "errors for unknown reasons"
comment.
author | FUJIWARA Katsunori <foozy@lares.dti.ne.jp> |
---|---|
date | Sun, 19 Jun 2016 02:17:33 +0900 |
parents | ead25aa27a43 |
children | 22fbca1d11ed |
line wrap: on
line source
# tags.py - read tag info from local repository # # Copyright 2009 Matt Mackall <mpm@selenic.com> # Copyright 2009 Greg Ward <greg@gerg.ca> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. # Currently this module only deals with reading and caching tags. # Eventually, it could take care of updating (adding/removing/moving) # tags too. from __future__ import absolute_import import array import errno import time from .node import ( bin, hex, nullid, short, ) from . import ( encoding, error, util, ) array = array.array # Tags computation can be expensive and caches exist to make it fast in # the common case. # # The "hgtagsfnodes1" cache file caches the .hgtags filenode values for # each revision in the repository. The file is effectively an array of # fixed length records. Read the docs for "hgtagsfnodescache" for technical # details. # # The .hgtags filenode cache grows in proportion to the length of the # changelog. The file is truncated when the # changelog is stripped. # # The purpose of the filenode cache is to avoid the most expensive part # of finding global tags, which is looking up the .hgtags filenode in the # manifest for each head. This can take dozens or over 100ms for # repositories with very large manifests. Multiplied by dozens or even # hundreds of heads and there is a significant performance concern. # # There also exist a separate cache file for each repository filter. # These "tags-*" files store information about the history of tags. # # The tags cache files consists of a cache validation line followed by # a history of tags. # # The cache validation line has the format: # # <tiprev> <tipnode> [<filteredhash>] # # <tiprev> is an integer revision and <tipnode> is a 40 character hex # node for that changeset. These redundantly identify the repository # tip from the time the cache was written. In addition, <filteredhash>, # if present, is a 40 character hex hash of the contents of the filtered # revisions for this filter. If the set of filtered revs changes, the # hash will change and invalidate the cache. # # The history part of the tags cache consists of lines of the form: # # <node> <tag> # # (This format is identical to that of .hgtags files.) # # <tag> is the tag name and <node> is the 40 character hex changeset # the tag is associated with. # # Tags are written sorted by tag name. # # Tags associated with multiple changesets have an entry for each changeset. # The most recent changeset (in terms of revlog ordering for the head # setting it) for each tag is last. def findglobaltags(ui, repo, alltags, tagtypes): '''Find global tags in a repo. "alltags" maps tag name to (node, hist) 2-tuples. "tagtypes" maps tag name to tag type. Global tags always have the "global" tag type. The "alltags" and "tagtypes" dicts are updated in place. Empty dicts should be passed in. The tags cache is read and updated as a side-effect of calling. ''' # This is so we can be lazy and assume alltags contains only global # tags when we pass it to _writetagcache(). assert len(alltags) == len(tagtypes) == 0, \ "findglobaltags() should be called first" (heads, tagfnode, valid, cachetags, shouldwrite) = _readtagcache(ui, repo) if cachetags is not None: assert not shouldwrite # XXX is this really 100% correct? are there oddball special # cases where a global tag should outrank a local tag but won't, # because cachetags does not contain rank info? _updatetags(cachetags, 'global', alltags, tagtypes) return seen = set() # set of fnode fctx = None for head in reversed(heads): # oldest to newest assert head in repo.changelog.nodemap, \ "tag cache returned bogus head %s" % short(head) fnode = tagfnode.get(head) if fnode and fnode not in seen: seen.add(fnode) if not fctx: fctx = repo.filectx('.hgtags', fileid=fnode) else: fctx = fctx.filectx(fnode) filetags = _readtags(ui, repo, fctx.data().splitlines(), fctx) _updatetags(filetags, 'global', alltags, tagtypes) # and update the cache (if necessary) if shouldwrite: _writetagcache(ui, repo, valid, alltags) def readlocaltags(ui, repo, alltags, tagtypes): '''Read local tags in repo. Update alltags and tagtypes.''' try: data = repo.vfs.read("localtags") except IOError as inst: if inst.errno != errno.ENOENT: raise return # localtags is in the local encoding; re-encode to UTF-8 on # input for consistency with the rest of this module. filetags = _readtags( ui, repo, data.splitlines(), "localtags", recode=encoding.fromlocal) # remove tags pointing to invalid nodes cl = repo.changelog for t in filetags.keys(): try: cl.rev(filetags[t][0]) except (LookupError, ValueError): del filetags[t] _updatetags(filetags, "local", alltags, tagtypes) def _readtaghist(ui, repo, lines, fn, recode=None, calcnodelines=False): '''Read tag definitions from a file (or any source of lines). This function returns two sortdicts with similar information: - the first dict, bintaghist, contains the tag information as expected by the _readtags function, i.e. a mapping from tag name to (node, hist): - node is the node id from the last line read for that name, - hist is the list of node ids previously associated with it (in file order). All node ids are binary, not hex. - the second dict, hextaglines, is a mapping from tag name to a list of [hexnode, line number] pairs, ordered from the oldest to the newest node. When calcnodelines is False the hextaglines dict is not calculated (an empty dict is returned). This is done to improve this function's performance in cases where the line numbers are not needed. ''' bintaghist = util.sortdict() hextaglines = util.sortdict() count = 0 def dbg(msg): ui.debug("%s, line %s: %s\n" % (fn, count, msg)) for nline, line in enumerate(lines): count += 1 if not line: continue try: (nodehex, name) = line.split(" ", 1) except ValueError: dbg("cannot parse entry") continue name = name.strip() if recode: name = recode(name) try: nodebin = bin(nodehex) except TypeError: dbg("node '%s' is not well formed" % nodehex) continue # update filetags if calcnodelines: # map tag name to a list of line numbers if name not in hextaglines: hextaglines[name] = [] hextaglines[name].append([nodehex, nline]) continue # map tag name to (node, hist) if name not in bintaghist: bintaghist[name] = [] bintaghist[name].append(nodebin) return bintaghist, hextaglines def _readtags(ui, repo, lines, fn, recode=None, calcnodelines=False): '''Read tag definitions from a file (or any source of lines). Returns a mapping from tag name to (node, hist). "node" is the node id from the last line read for that name. "hist" is the list of node ids previously associated with it (in file order). All node ids are binary, not hex. ''' filetags, nodelines = _readtaghist(ui, repo, lines, fn, recode=recode, calcnodelines=calcnodelines) # util.sortdict().__setitem__ is much slower at replacing then inserting # new entries. The difference can matter if there are thousands of tags. # Create a new sortdict to avoid the performance penalty. newtags = util.sortdict() for tag, taghist in filetags.items(): newtags[tag] = (taghist[-1], taghist[:-1]) return newtags def _updatetags(filetags, tagtype, alltags, tagtypes): '''Incorporate the tag info read from one file into the two dictionaries, alltags and tagtypes, that contain all tag info (global across all heads plus local).''' for name, nodehist in filetags.iteritems(): if name not in alltags: alltags[name] = nodehist tagtypes[name] = tagtype continue # we prefer alltags[name] if: # it supersedes us OR # mutual supersedes and it has a higher rank # otherwise we win because we're tip-most anode, ahist = nodehist bnode, bhist = alltags[name] if (bnode != anode and anode in bhist and (bnode not in ahist or len(bhist) > len(ahist))): anode = bnode else: tagtypes[name] = tagtype ahist.extend([n for n in bhist if n not in ahist]) alltags[name] = anode, ahist def _filename(repo): """name of a tagcache file for a given repo or repoview""" filename = 'cache/tags2' if repo.filtername: filename = '%s-%s' % (filename, repo.filtername) return filename def _readtagcache(ui, repo): '''Read the tag cache. Returns a tuple (heads, fnodes, validinfo, cachetags, shouldwrite). If the cache is completely up-to-date, "cachetags" is a dict of the form returned by _readtags() and "heads", "fnodes", and "validinfo" are None and "shouldwrite" is False. If the cache is not up to date, "cachetags" is None. "heads" is a list of all heads currently in the repository, ordered from tip to oldest. "validinfo" is a tuple describing cache validation info. This is used when writing the tags cache. "fnodes" is a mapping from head to .hgtags filenode. "shouldwrite" is True. If the cache is not up to date, the caller is responsible for reading tag info from each returned head. (See findglobaltags().) ''' from . import scmutil # avoid cycle try: cachefile = repo.vfs(_filename(repo), 'r') # force reading the file for static-http cachelines = iter(cachefile) except IOError: cachefile = None cacherev = None cachenode = None cachehash = None if cachefile: try: validline = next(cachelines) validline = validline.split() cacherev = int(validline[0]) cachenode = bin(validline[1]) if len(validline) > 2: cachehash = bin(validline[2]) except Exception: # corruption of the cache, just recompute it. pass tipnode = repo.changelog.tip() tiprev = len(repo.changelog) - 1 # Case 1 (common): tip is the same, so nothing has changed. # (Unchanged tip trivially means no changesets have been added. # But, thanks to localrepository.destroyed(), it also means none # have been destroyed by strip or rollback.) if (cacherev == tiprev and cachenode == tipnode and cachehash == scmutil.filteredhash(repo, tiprev)): tags = _readtags(ui, repo, cachelines, cachefile.name) cachefile.close() return (None, None, None, tags, False) if cachefile: cachefile.close() # ignore rest of file valid = (tiprev, tipnode, scmutil.filteredhash(repo, tiprev)) repoheads = repo.heads() # Case 2 (uncommon): empty repo; get out quickly and don't bother # writing an empty cache. if repoheads == [nullid]: return ([], {}, valid, {}, False) # Case 3 (uncommon): cache file missing or empty. # Case 4 (uncommon): tip rev decreased. This should only happen # when we're called from localrepository.destroyed(). Refresh the # cache so future invocations will not see disappeared heads in the # cache. # Case 5 (common): tip has changed, so we've added/replaced heads. # As it happens, the code to handle cases 3, 4, 5 is the same. # N.B. in case 4 (nodes destroyed), "new head" really means "newly # exposed". if not len(repo.file('.hgtags')): # No tags have ever been committed, so we can avoid a # potentially expensive search. return ([], {}, valid, None, True) starttime = time.time() # Now we have to lookup the .hgtags filenode for every new head. # This is the most expensive part of finding tags, so performance # depends primarily on the size of newheads. Worst case: no cache # file, so newheads == repoheads. fnodescache = hgtagsfnodescache(repo.unfiltered()) cachefnode = {} for head in reversed(repoheads): fnode = fnodescache.getfnode(head) if fnode != nullid: cachefnode[head] = fnode fnodescache.write() duration = time.time() - starttime ui.log('tagscache', '%d/%d cache hits/lookups in %0.4f ' 'seconds\n', fnodescache.hitcount, fnodescache.lookupcount, duration) # Caller has to iterate over all heads, but can use the filenodes in # cachefnode to get to each .hgtags revision quickly. return (repoheads, cachefnode, valid, None, True) def _writetagcache(ui, repo, valid, cachetags): filename = _filename(repo) try: cachefile = repo.vfs(filename, 'w', atomictemp=True) except (OSError, IOError): return ui.log('tagscache', 'writing .hg/%s with %d tags\n', filename, len(cachetags)) if valid[2]: cachefile.write('%d %s %s\n' % (valid[0], hex(valid[1]), hex(valid[2]))) else: cachefile.write('%d %s\n' % (valid[0], hex(valid[1]))) # Tag names in the cache are in UTF-8 -- which is the whole reason # we keep them in UTF-8 throughout this module. If we converted # them local encoding on input, we would lose info writing them to # the cache. for (name, (node, hist)) in sorted(cachetags.iteritems()): for n in hist: cachefile.write("%s %s\n" % (hex(n), name)) cachefile.write("%s %s\n" % (hex(node), name)) try: cachefile.close() except (OSError, IOError): pass _fnodescachefile = 'cache/hgtagsfnodes1' _fnodesrecsize = 4 + 20 # changeset fragment + filenode _fnodesmissingrec = '\xff' * 24 class hgtagsfnodescache(object): """Persistent cache mapping revisions to .hgtags filenodes. The cache is an array of records. Each item in the array corresponds to a changelog revision. Values in the array contain the first 4 bytes of the node hash and the 20 bytes .hgtags filenode for that revision. The first 4 bytes are present as a form of verification. Repository stripping and rewriting may change the node at a numeric revision in the changelog. The changeset fragment serves as a verifier to detect rewriting. This logic is shared with the rev branch cache (see branchmap.py). The instance holds in memory the full cache content but entries are only parsed on read. Instances behave like lists. ``c[i]`` works where i is a rev or changeset node. Missing indexes are populated automatically on access. """ def __init__(self, repo): assert repo.filtername is None self._repo = repo # Only for reporting purposes. self.lookupcount = 0 self.hitcount = 0 self._raw = array('c') try: data = repo.vfs.read(_fnodescachefile) except (OSError, IOError): data = "" self._raw.fromstring(data) # The end state of self._raw is an array that is of the exact length # required to hold a record for every revision in the repository. # We truncate or extend the array as necessary. self._dirtyoffset is # defined to be the start offset at which we need to write the output # file. This offset is also adjusted when new entries are calculated # for array members. cllen = len(repo.changelog) wantedlen = cllen * _fnodesrecsize rawlen = len(self._raw) self._dirtyoffset = None if rawlen < wantedlen: self._dirtyoffset = rawlen self._raw.extend('\xff' * (wantedlen - rawlen)) elif rawlen > wantedlen: # There's no easy way to truncate array instances. This seems # slightly less evil than copying a potentially large array slice. for i in range(rawlen - wantedlen): self._raw.pop() self._dirtyoffset = len(self._raw) def getfnode(self, node, computemissing=True): """Obtain the filenode of the .hgtags file at a specified revision. If the value is in the cache, the entry will be validated and returned. Otherwise, the filenode will be computed and returned unless "computemissing" is False, in which case None will be returned without any potentially expensive computation being performed. If an .hgtags does not exist at the specified revision, nullid is returned. """ ctx = self._repo[node] rev = ctx.rev() self.lookupcount += 1 offset = rev * _fnodesrecsize record = self._raw[offset:offset + _fnodesrecsize].tostring() properprefix = node[0:4] # Validate and return existing entry. if record != _fnodesmissingrec: fileprefix = record[0:4] if fileprefix == properprefix: self.hitcount += 1 return record[4:] # Fall through. # If we get here, the entry is either missing or invalid. if not computemissing: return None # Populate missing entry. try: fnode = ctx.filenode('.hgtags') except error.LookupError: # No .hgtags file on this revision. fnode = nullid self._writeentry(offset, properprefix, fnode) return fnode def setfnode(self, node, fnode): """Set the .hgtags filenode for a given changeset.""" assert len(fnode) == 20 ctx = self._repo[node] # Do a lookup first to avoid writing if nothing has changed. if self.getfnode(ctx.node(), computemissing=False) == fnode: return self._writeentry(ctx.rev() * _fnodesrecsize, node[0:4], fnode) def _writeentry(self, offset, prefix, fnode): # Slices on array instances only accept other array. entry = array('c', prefix + fnode) self._raw[offset:offset + _fnodesrecsize] = entry # self._dirtyoffset could be None. self._dirtyoffset = min(self._dirtyoffset, offset) or 0 def write(self): """Perform all necessary writes to cache file. This may no-op if no writes are needed or if a write lock could not be obtained. """ if self._dirtyoffset is None: return data = self._raw[self._dirtyoffset:] if not data: return repo = self._repo try: lock = repo.wlock(wait=False) except error.LockError: repo.ui.log('tagscache', 'not writing .hg/%s because lock cannot be acquired\n' % (_fnodescachefile)) return try: f = repo.vfs.open(_fnodescachefile, 'ab') try: # if the file has been truncated actualoffset = f.tell() if actualoffset < self._dirtyoffset: self._dirtyoffset = actualoffset data = self._raw[self._dirtyoffset:] f.seek(self._dirtyoffset) f.truncate() repo.ui.log('tagscache', 'writing %d bytes to %s\n' % ( len(data), _fnodescachefile)) f.write(data) self._dirtyoffset = None finally: f.close() except (IOError, OSError) as inst: repo.ui.log('tagscache', "couldn't write %s: %s\n" % ( _fnodescachefile, inst)) finally: lock.release()