changelog: optimize delayed updates for clone vs pull

pull index updates get redirected to memory, then appended on finalize
clone index updates get sent to 00changelog.i.a, then renamed on finalize

mercurial/changelog.py

@@ -1,184 +1,196 b''
 # changelog.py - changelog class for mercurial
 #
 # Copyright 2005, 2006 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms
 # of the GNU General Public License, incorporated herein by reference.
 
 from revlog import *
 from i18n import _
 import os, time, util
 
 def _string_escape(text):
     """
     >>> d = {'nl': chr(10), 'bs': chr(92), 'cr': chr(13), 'nul': chr(0)}
     >>> s = "ab%(nl)scd%(bs)s%(bs)sn%(nul)sab%(cr)scd%(bs)s%(nl)s" % d
     >>> s
     'ab\\ncd\\\\\\\\n\\x00ab\\rcd\\\\\\n'
     >>> res = _string_escape(s)
     >>> s == _string_unescape(res)
     True
     """
     # subset of the string_escape codec
     text = text.replace('\\', '\\\\').replace('\n', '\\n').replace('\r', '\\r')
     return text.replace('\0', '\\0')
 
 def _string_unescape(text):
     return text.decode('string_escape')
 
 class appender:
     '''the changelog index must be update last on disk, so we use this class
     to delay writes to it'''
     def __init__(self, fp, buf):
         self.data = buf
         self.fp = fp
         self.offset = fp.tell()
         self.size = util.fstat(fp).st_size
 
     def end(self):
         return self.size + len("".join(self.data))
     def tell(self):
         return self.offset
     def flush(self):
         pass
     def close(self):
         close(self.fp)
 
     def seek(self, offset, whence=0):
         '''virtual file offset spans real file and data'''
         if whence == 0:
             self.offset = offset
         elif whence == 1:
             self.offset += offset
         elif whence == 2:
             self.offset = self.end() + offset
         if self.offset < self.size:
             self.fp.seek(self.offset)
 
     def read(self, count=-1):
         '''only trick here is reads that span real file and data'''
         ret = ""
         old_offset = self.offset
         if self.offset < self.size:
             s = self.fp.read(count)
             ret = s
             self.offset += len(s)
             if count > 0:
                 count -= len(s)
         if count != 0:
             doff = self.offset - self.size
             self.data.insert(0, "".join(self.data))
             del self.data[1:]
             s = self.data[0][doff:doff+count]
             self.offset += len(s)
             ret += s
         return ret
 
     def write(self, s):
         self.data.append(s)
         self.offset += len(s)
 
 class changelog(revlog):
     def __init__(self, opener):
         revlog.__init__(self, opener, "00changelog.i")
 
     def delayupdate(self):
         "delay visibility of index updates to other readers"
         self._realopener = self.opener
-        self.opener = self._appendopener
+        self.opener = self._delayopener
+        self._delaycount = self.count()
         self._delaybuf = []
+        self._delayname = None
 
     def finalize(self, tr):
         "finalize index updates"
         self.opener = self._realopener
-        if self._delaybuf:
+        # move redirected index data back into place
+        if self._delayname:
+            util.rename(self._delayname + ".a", self._delayname)
+        elif self._delaybuf:
             fp = self.opener(self.indexfile, 'a')
             fp.write("".join(self._delaybuf))
             fp.close()
             del self._delaybuf
+        # split when we're done
         self.checkinlinesize(tr)
 
-    def _appendopener(self, name, mode='r'):
+    def _delayopener(self, name, mode='r'):
         fp = self._realopener(name, mode)
+        # only divert the index
         if not name == self.indexfile:
             return fp
+        # if we're doing an initial clone, divert to another file
+        if self._delaycount == 0:
+            self._delayname = fp.name
+            return self._realopener(name + ".a", mode)
+        # otherwise, divert to memory
         return appender(fp, self._delaybuf)
 
     def checkinlinesize(self, tr, fp=None):
-        if self.opener == self._appendopener:
+        if self.opener == self._delayopener:
             return
         return revlog.checkinlinesize(self, tr, fp)
 
     def decode_extra(self, text):
         extra = {}
         for l in text.split('\0'):
             if not l:
                 continue
             k, v = _string_unescape(l).split(':', 1)
             extra[k] = v
         return extra
 
     def encode_extra(self, d):
         items = [_string_escape(":".join(t)) for t in d.iteritems()]
         return "\0".join(items)
 
     def extract(self, text):
         """
         format used:
         nodeid\n        : manifest node in ascii
         user\n          : user, no \n or \r allowed
         time tz extra\n : date (time is int or float, timezone is int)
                         : extra is metadatas, encoded and separated by '\0'
                         : older versions ignore it
         files\n\n       : files modified by the cset, no \n or \r allowed
         (.*)            : comment (free text, ideally utf-8)
 
         changelog v0 doesn't use extra
         """
         if not text:
             return (nullid, "", (0, 0), [], "", {'branch': 'default'})
         last = text.index("\n\n")
         desc = util.tolocal(text[last + 2:])
         l = text[:last].split('\n')
         manifest = bin(l[0])
         user = util.tolocal(l[1])
 
         extra_data = l[2].split(' ', 2)
         if len(extra_data) != 3:
             time = float(extra_data.pop(0))
             try:
                 # various tools did silly things with the time zone field.
                 timezone = int(extra_data[0])
             except:
                 timezone = 0
             extra = {}
         else:
             time, timezone, extra = extra_data
             time, timezone = float(time), int(timezone)
             extra = self.decode_extra(extra)
         if not extra.get('branch'):
             extra['branch'] = 'default'
         files = l[3:]
         return (manifest, user, (time, timezone), files, desc, extra)
 
     def read(self, node):
         return self.extract(self.revision(node))
 
     def add(self, manifest, list, desc, transaction, p1=None, p2=None,
                   user=None, date=None, extra={}):
 
         user, desc = util.fromlocal(user), util.fromlocal(desc)
 
         if date:
             parseddate = "%d %d" % util.parsedate(date)
         else:
             parseddate = "%d %d" % util.makedate()
         if extra and extra.get("branch") in ("default", ""):
             del extra["branch"]
         if extra:
             extra = self.encode_extra(extra)
             parseddate = "%s %s" % (parseddate, extra)
         list.sort()
         l = [hex(manifest), user, parseddate] + list + ["", desc]
         text = "\n".join(l)
         return self.addrevision(text, transaction, self.count(), p1, p2)

tests/test-hup.out

@@ -1,7 +1,7 b''
 0
 0
 adding changesets
 killed!
 transaction abort!
 rollback completed
-.hg/00changelog.i .hg/journal.dirstate .hg/requires .hg/store .hg/store/00changelog.i
+.hg/00changelog.i .hg/journal.dirstate .hg/requires .hg/store .hg/store/00changelog.i .hg/store/00changelog.i.a