upstream/mercurial-mirror Files · mercurial/revlogutils/constants.py

nodemap: gate the feature behind a new requirement...

nodemap: gate the feature behind a new requirement Now that the feature is working smoothly, a question was still open, should we gate the feature behind a new requirement or just treat it as a cache to be warmed by those who can and ignored by other. The advantage of using the cache approach is a transparent upgrade/downgrade story, making the feature easier to move to. However having out of date cache can come with a significant performance hit for process who expect an up to date cache but found none. In this case the file needs to be stored under `.hg/cache`. The "requirement" approach guarantee that the persistent nodemap is up to date. However, it comes with a less flexible activation story since an explicite upgrade is required. In this case the file can be stored in `.hg/store`. This wiki page is relevant to this questions: https://www.mercurial-scm.org/wiki/ComputedIndexPlan So which one should we take? Another element came into plan, the persistent nodemap use the `add` method of the transaction, it is used to keep track of a file content before a transaction in case we need to rollback it back. It turns out that the `transaction.add` API does not support file stored anywhere than `.hg/store`. Making it support file stored elsewhere is possible, require a change in on disk transaction format. Updating on disk file requires… introducing a new requirements. As a result, we pick the second option "gating the persistent nodemap behind a new requirements". Differential Revision: https://phab.mercurial-scm.org/D8417

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      # revlogdeltas.py - constant used for revlog logic

      #

      # Copyright 2005-2007 Matt Mackall <mpm@selenic.com>

      # Copyright 2018 Octobus <contact@octobus.net>

      #

      # This software may be used and distributed according to the terms of the

      # GNU General Public License version 2 or any later version.

      """Helper class to compute deltas stored inside revlogs"""

      from __future__ import absolute_import

      from ..interfaces import repository

      # revlog header flags

      REVLOGV0 = 0

      REVLOGV1 = 1

      # 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 = FLAG_INLINE_DATA

      # revlog index flags

      # For historical reasons, revlog's internal flags were exposed via the

      # wire protocol and are even exposed in parts of the storage APIs.

      # revision has censor metadata, must be verified

      REVIDX_ISCENSORED = repository.REVISION_FLAG_CENSORED

      # revision hash does not match data (narrowhg)

      REVIDX_ELLIPSIS = repository.REVISION_FLAG_ELLIPSIS

      # revision data is stored externally

      REVIDX_EXTSTORED = repository.REVISION_FLAG_EXTSTORED

      # revision data contains extra metadata not part of the official digest

      REVIDX_SIDEDATA = repository.REVISION_FLAG_SIDEDATA

      REVIDX_DEFAULT_FLAGS = 0

      # stable order in which flags need to be processed and their processors applied

      REVIDX_FLAGS_ORDER = [

          REVIDX_ISCENSORED,

          REVIDX_ELLIPSIS,

          REVIDX_EXTSTORED,

          REVIDX_SIDEDATA,

      ]

      # bitmark for flags that could cause rawdata content change

      REVIDX_RAWTEXT_CHANGING_FLAGS = (

          REVIDX_ISCENSORED | REVIDX_EXTSTORED | REVIDX_SIDEDATA

      )

      SPARSE_REVLOG_MAX_CHAIN_LENGTH = 1000

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				# revlogdeltas.py - constant used for revlog logic
				#
				# Copyright 2005-2007 Matt Mackall <mpm@selenic.com>
				# Copyright 2018 Octobus <contact@octobus.net>
				#
				# This software may be used and distributed according to the terms of the
				# GNU General Public License version 2 or any later version.
				"""Helper class to compute deltas stored inside revlogs"""

				from __future__ import absolute_import

				from ..interfaces import repository

				# revlog header flags
				REVLOGV0 = 0
				REVLOGV1 = 1
				# 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 = FLAG_INLINE_DATA

				# revlog index flags

				# For historical reasons, revlog's internal flags were exposed via the
				# wire protocol and are even exposed in parts of the storage APIs.

				# revision has censor metadata, must be verified
				REVIDX_ISCENSORED = repository.REVISION_FLAG_CENSORED
				# revision hash does not match data (narrowhg)
				REVIDX_ELLIPSIS = repository.REVISION_FLAG_ELLIPSIS
				# revision data is stored externally
				REVIDX_EXTSTORED = repository.REVISION_FLAG_EXTSTORED
				# revision data contains extra metadata not part of the official digest
				REVIDX_SIDEDATA = repository.REVISION_FLAG_SIDEDATA
				REVIDX_DEFAULT_FLAGS = 0
				# stable order in which flags need to be processed and their processors applied
				REVIDX_FLAGS_ORDER = [
				REVIDX_ISCENSORED,
				REVIDX_ELLIPSIS,
				REVIDX_EXTSTORED,
				REVIDX_SIDEDATA,
				]

				# bitmark for flags that could cause rawdata content change
				REVIDX_RAWTEXT_CHANGING_FLAGS = (
				REVIDX_ISCENSORED \| REVIDX_EXTSTORED \| REVIDX_SIDEDATA
				)

				SPARSE_REVLOG_MAX_CHAIN_LENGTH = 1000