comparison mercurial/dirstate.py @ 48793:6e559391f96e

tracked-key: remove the dual write and rename to tracked-hint

The dual-write approach was mostly useless. As explained in the previous version
of the help, the key had to be read twice before we could cache a value.

However this "read twice" limitation actually also apply to any usage of the
key. If some operation wants to rely of the "same value == same tracked set"
property it would need to read the value before, and after running that
operation (or at least, after, in all cases). So it cannot be sure the operation
it did is "valid" until checking the key after the operation. As a resultat such
operation can only be read-only or rollbackable.

This reduce the utility of the "same value == same tracked set" a lot.

So it seems simpler to drop the double write and to update the documentation to
highlight that this file does not garantee race-free operation. As a result the
"key" is demoted to a "hint".

Documentation is updated accordingly.

Differential Revision: https://phab.mercurial-scm.org/D12201

48792:8bbb1abb9d19

        root,
        validate,
        sparsematchfn,
        nodeconstants,
        use_dirstate_v2,
        use_tracked_key=False,
    ):
        """Create a new dirstate object.

        opener is an open()-like callable that can be used to open the
        dirstate file; root is the root of the directory tracked by
        the dirstate.
        """
        self._use_dirstate_v2 = use_dirstate_v2
        self._use_tracked_key = use_tracked_key
        self._nodeconstants = nodeconstants
        self._opener = opener
        self._validate = validate
        self._root = root
        self._sparsematchfn = sparsematchfn

        self._dirty_tracked_set = False
        self._ui = ui
        self._filecache = {}
        self._parentwriters = 0
        self._filename = b'dirstate'
        self._filename_tk = b'dirstate-tracked-key'
        self._pendingfilename = b'%s.pending' % self._filename
        self._plchangecallbacks = {}
        self._origpl = None
        self._mapcls = dirstatemap.dirstatemap
        # Access and cache cwd early, so we don't access it for the first time

    def write(self, tr):
        if not self._dirty:
            return

        write_key = self._use_tracked_key and self._dirty_tracked_set
        if tr:
            # delay writing in-memory changes out
            if write_key:
                tr.addfilegenerator(
                    b'dirstate-0-key-pre',
                    (self._filename_tk,),
                    lambda f: self._write_tracked_key(tr, f),
                    location=b'plain',
                    post_finalize=True,
                )
            tr.addfilegenerator(
                b'dirstate-1-main',
                (self._filename,),
                lambda f: self._writedirstate(tr, f),
                location=b'plain',
                post_finalize=True,
            )
            if write_key:
                tr.addfilegenerator(
                    b'dirstate-2-key-post',
                    (self._filename_tk,),
                    lambda f: self._write_tracked_key(tr, f),
                    location=b'plain',
                    post_finalize=True,
                )
            return

        file = lambda f: self._opener(f, b"w", atomictemp=True, checkambig=True)
        if write_key:
            # we change the key-file before changing the dirstate to make sure
            # reading invalidate there cache before we start writing
            with file(self._filename_tk) as f:
                self._write_tracked_key(tr, f)
        with file(self._filename) as f:
            self._writedirstate(tr, f)
        if write_key:
            # we update the key-file after writing to make sure reader have a
            # key that match the newly written content
            with file(self._filename_tk) as f:
                self._write_tracked_key(tr, f)

    def delete_tracked_key(self):
        """remove the tracked_key file

        To be used by format downgrades operation"""
        self._opener.unlink(self._filename_tk)
        self._use_tracked_key = False

    def addparentchangecallback(self, category, callback):
        """add a callback to be called when the wd parents are changed

        Callback will be called with the following arguments:

            self._origpl = None
        self._map.write(tr, st)
        self._dirty = False
        self._dirty_tracked_set = False

    def _write_tracked_key(self, tr, f):
        key = node.hex(uuid.uuid4().bytes)
        f.write(b"1\n%s\n" % key)  # 1 is the format version

    def _dirignore(self, f):
        if self._ignore(f):

48793:6e559391f96e

        root,
        validate,
        sparsematchfn,
        nodeconstants,
        use_dirstate_v2,
        use_tracked_hint=False,
    ):
        """Create a new dirstate object.

        opener is an open()-like callable that can be used to open the
        dirstate file; root is the root of the directory tracked by
        the dirstate.
        """
        self._use_dirstate_v2 = use_dirstate_v2
        self._use_tracked_hint = use_tracked_hint
        self._nodeconstants = nodeconstants
        self._opener = opener
        self._validate = validate
        self._root = root
        self._sparsematchfn = sparsematchfn

        self._dirty_tracked_set = False
        self._ui = ui
        self._filecache = {}
        self._parentwriters = 0
        self._filename = b'dirstate'
        self._filename_th = b'dirstate-tracked-hint'
        self._pendingfilename = b'%s.pending' % self._filename
        self._plchangecallbacks = {}
        self._origpl = None
        self._mapcls = dirstatemap.dirstatemap
        # Access and cache cwd early, so we don't access it for the first time

    def write(self, tr):
        if not self._dirty:
            return

        write_key = self._use_tracked_hint and self._dirty_tracked_set
        if tr:
            # delay writing in-memory changes out
            tr.addfilegenerator(
                b'dirstate-1-main',
                (self._filename,),
                lambda f: self._writedirstate(tr, f),
                location=b'plain',
                post_finalize=True,
            )
            if write_key:
                tr.addfilegenerator(
                    b'dirstate-2-key-post',
                    (self._filename_th,),
                    lambda f: self._write_tracked_hint(tr, f),
                    location=b'plain',
                    post_finalize=True,
                )
            return

        file = lambda f: self._opener(f, b"w", atomictemp=True, checkambig=True)
        with file(self._filename) as f:
            self._writedirstate(tr, f)
        if write_key:
            # we update the key-file after writing to make sure reader have a
            # key that match the newly written content
            with file(self._filename_th) as f:
                self._write_tracked_hint(tr, f)

    def delete_tracked_hint(self):
        """remove the tracked_hint file

        To be used by format downgrades operation"""
        self._opener.unlink(self._filename_th)
        self._use_tracked_hint = False

    def addparentchangecallback(self, category, callback):
        """add a callback to be called when the wd parents are changed

        Callback will be called with the following arguments:

            self._origpl = None
        self._map.write(tr, st)
        self._dirty = False
        self._dirty_tracked_set = False

    def _write_tracked_hint(self, tr, f):
        key = node.hex(uuid.uuid4().bytes)
        f.write(b"1\n%s\n" % key)  # 1 is the format version

    def _dirignore(self, f):
        if self._ignore(f):