changeset 41202:e7a2cc84dbc0

revlog: always enable generaldelta on version 2 revlogs This commit starts the process of diverging version 2 revlogs from version 1 revlogs. generaldelta is a useful feature and has been enabled by default for ages. I can't think of a good reason why the feature should be disabled. Yes, it is true changelogs today don't have generaldelta enabled. But that's because they don't have delta chains enabled, so generaldelta makes no sense there. This commit makes generaldelta always enabled on version 2 revlogs. As part of this, one-off code in changelog.py mucking with revlog.version had to be made conditional on the revlog version, as we don't want to change revlog feature flags on version 2 revlogs. The fact this code exists is horrible and stems from revlog options being shared by the opener. We probably want a better API here. But that can wait for another patch. Differential Revision: https://phab.mercurial-scm.org/D5561
author Gregory Szorc <gregory.szorc@gmail.com>
date Wed, 09 Jan 2019 17:41:36 -0800
parents 6439cefaeb64
children d0de4fdd87aa
files mercurial/changelog.py mercurial/help/internals/revlogs.txt mercurial/localrepo.py mercurial/revlog.py mercurial/revlogutils/constants.py tests/test-revlog-v2.t
diffstat 6 files changed, 30 insertions(+), 15 deletions(-) [+]
line wrap: on
line diff
--- a/mercurial/changelog.py	Wed Jan 09 15:45:17 2019 -0800
+++ b/mercurial/changelog.py	Wed Jan 09 17:41:36 2019 -0800
@@ -295,8 +295,9 @@
         revlog.revlog.__init__(self, opener, indexfile, datafile=datafile,
                                checkambig=True, mmaplargeindex=True)
 
-        if self._initempty:
-            # changelogs don't benefit from generaldelta
+        if self._initempty and (self.version & 0xFFFF == revlog.REVLOGV1):
+            # changelogs don't benefit from generaldelta.
+
             self.version &= ~revlog.FLAG_GENERALDELTA
             self._generaldelta = False
 
--- a/mercurial/help/internals/revlogs.txt	Wed Jan 09 15:45:17 2019 -0800
+++ b/mercurial/help/internals/revlogs.txt	Wed Jan 09 17:41:36 2019 -0800
@@ -66,8 +66,6 @@
 
 0
    Store revision data inline.
-1
-   Generaldelta encoding.
 
 The following header values are common:
 
@@ -159,8 +157,10 @@
 
 (In development. Format not finalized or stable.)
 
-Version 2 is currently identical to version 1. This will obviously
-change.
+Version 2 is identical to version 2 with the following differences.
+
+There is no dedicated *generaldelta* revlog format flag. Instead,
+the feature is implied enabled by default.
 
 Delta Chains
 ============
--- a/mercurial/localrepo.py	Wed Jan 09 15:45:17 2019 -0800
+++ b/mercurial/localrepo.py	Wed Jan 09 17:41:36 2019 -0800
@@ -363,7 +363,7 @@
 
 # Increment the sub-version when the revlog v2 format changes to lock out old
 # clients.
-REVLOGV2_REQUIREMENT = 'exp-revlogv2.0'
+REVLOGV2_REQUIREMENT = 'exp-revlogv2.1'
 
 # A repository with the sparserevlog feature will have delta chains that
 # can spread over a larger span. Sparse reading cuts these large spans into
--- a/mercurial/revlog.py	Wed Jan 09 15:45:17 2019 -0800
+++ b/mercurial/revlog.py	Wed Jan 09 17:41:36 2019 -0800
@@ -387,8 +387,7 @@
         opts = getattr(opener, 'options', {}) or {}
 
         if 'revlogv2' in opts:
-            # version 2 revlogs always use generaldelta.
-            versionflags = REVLOGV2 | FLAG_GENERALDELTA | FLAG_INLINE_DATA
+            versionflags = REVLOGV2 | FLAG_INLINE_DATA
         elif 'revlogv1' in opts:
             versionflags = REVLOGV1 | FLAG_INLINE_DATA
             if 'generaldelta' in opts:
@@ -451,25 +450,38 @@
                 raise
 
         self.version = versionflags
-        self._inline = versionflags & FLAG_INLINE_DATA
-        self._generaldelta = versionflags & FLAG_GENERALDELTA
+
         flags = versionflags & ~0xFFFF
         fmt = versionflags & 0xFFFF
+
         if fmt == REVLOGV0:
             if flags:
                 raise error.RevlogError(_('unknown flags (%#04x) in version %d '
                                           'revlog %s') %
                                         (flags >> 16, fmt, self.indexfile))
+
+            self._inline = False
+            self._generaldelta = False
+
         elif fmt == REVLOGV1:
             if flags & ~REVLOGV1_FLAGS:
                 raise error.RevlogError(_('unknown flags (%#04x) in version %d '
                                           'revlog %s') %
                                         (flags >> 16, fmt, self.indexfile))
+
+            self._inline = versionflags & FLAG_INLINE_DATA
+            self._generaldelta = versionflags & FLAG_GENERALDELTA
+
         elif fmt == REVLOGV2:
             if flags & ~REVLOGV2_FLAGS:
                 raise error.RevlogError(_('unknown flags (%#04x) in version %d '
                                           'revlog %s') %
                                         (flags >> 16, fmt, self.indexfile))
+
+            self._inline = versionflags & FLAG_INLINE_DATA
+            # generaldelta implied by version 2 revlogs.
+            self._generaldelta = True
+
         else:
             raise error.RevlogError(_('unknown version (%d) in revlog %s') %
                                     (fmt, self.indexfile))
--- a/mercurial/revlogutils/constants.py	Wed Jan 09 15:45:17 2019 -0800
+++ b/mercurial/revlogutils/constants.py	Wed Jan 09 17:41:36 2019 -0800
@@ -20,13 +20,15 @@
 # Dummy value until file format is finalized.
 # Reminder: change the bounds check in revlog.__init__ when this is changed.
 REVLOGV2 = 0xDEAD
+# Shared across v1 and v2.
 FLAG_INLINE_DATA = (1 << 16)
+# Only used by v1, implied by v2.
 FLAG_GENERALDELTA = (1 << 17)
 REVLOG_DEFAULT_FLAGS = FLAG_INLINE_DATA
 REVLOG_DEFAULT_FORMAT = REVLOGV1
 REVLOG_DEFAULT_VERSION = REVLOG_DEFAULT_FORMAT | REVLOG_DEFAULT_FLAGS
 REVLOGV1_FLAGS = FLAG_INLINE_DATA | FLAG_GENERALDELTA
-REVLOGV2_FLAGS = REVLOGV1_FLAGS
+REVLOGV2_FLAGS = FLAG_INLINE_DATA
 
 # revlog index flags
 
--- a/tests/test-revlog-v2.t	Wed Jan 09 15:45:17 2019 -0800
+++ b/tests/test-revlog-v2.t	Wed Jan 09 17:41:36 2019 -0800
@@ -22,7 +22,7 @@
   $ cd empty-repo
   $ cat .hg/requires
   dotencode
-  exp-revlogv2.0
+  exp-revlogv2.1
   fncache
   sparserevlog
   store
@@ -54,7 +54,7 @@
   date:        Thu Jan 01 00:00:00 1970 +0000
   summary:     initial
   
-Header written as expected (changelog always disables generaldelta)
+Header written as expected
 
   $ f --hexdump --bytes 4 .hg/store/00changelog.i
   .hg/store/00changelog.i:
@@ -62,4 +62,4 @@
 
   $ f --hexdump --bytes 4 .hg/store/data/foo.i
   .hg/store/data/foo.i:
-  0000: 00 03 de ad                                     |....|
+  0000: 00 01 de ad                                     |....|