comparison mercurial/revlogutils/constants.py @ 47234:616b8f412676

revlogv2: introduce a very basic docket file

This is the first stone toward using a docket file in revlogv2. Right now the
docket is very basic and only store the version number (which is -also- stored
into the index file…) and the other files have fixed name. This new
implementation break transactionally… but they are no test checking
transactionally for revlogv2… So I take this as an opportunity to start small.
They are no usage of revlogv2 outside of tests anyway.

The docket keeps the `.i` naming used by previous version index to preserve a
unique entry point. We could decide to use a different name and look it up
first, or to fully rework this in a future "store" version. However that does
not seems necessary right now.

We will re-introduces transactionality (and associated testing…) in a later
changesets.


A long list of TODOs have been added to the relevant comment.

Differential Revision: https://phab.mercurial-scm.org/D10624

47233:bcafcd779d2e

FEATURES_BY_VERSION = {
    REVLOGV0: {
        b'inline': _no,
        b'generaldelta': _no,
        b'sidedata': False,
    },
    REVLOGV1: {
        b'inline': _from_flag(FLAG_INLINE_DATA),
        b'generaldelta': _from_flag(FLAG_GENERALDELTA),
        b'sidedata': False,
    },
    REVLOGV2: {
        # There is a bug in the transaction handling when going from an
        # inline revlog to a separate index and data file. Turn it off until
        # it's fixed, since v2 revlogs sometimes get rewritten on exchange.
        # See issue6485
        b'inline': _no,
        b'generaldelta': _yes,
        b'sidedata': True,
    },
}

SPARSE_REVLOG_MAX_CHAIN_LENGTH = 1000

47234:616b8f412676

FEATURES_BY_VERSION = {
    REVLOGV0: {
        b'inline': _no,
        b'generaldelta': _no,
        b'sidedata': False,
        b'docket': False,
    },
    REVLOGV1: {
        b'inline': _from_flag(FLAG_INLINE_DATA),
        b'generaldelta': _from_flag(FLAG_GENERALDELTA),
        b'sidedata': False,
        b'docket': False,
    },
    REVLOGV2: {
        # The point of inline-revlog is to reduce the number of files used in
        # the store. Using a docket defeat this purpose. So we needs other
        # means to reduce the number of files for revlogv2.
        b'inline': _no,
        b'generaldelta': _yes,
        b'sidedata': True,
        b'docket': True,
    },
}

SPARSE_REVLOG_MAX_CHAIN_LENGTH = 1000