swh.storage.algos.revisions_walker module

class swh.storage.algos.revisions_walker.RevisionsWalker(storage, rev_start, max_revs=None, state=None)[source]

Bases: object

Abstract base class encapsulating the logic to walk across a revisions history starting from a given one.

It defines an iterator returning the revisions according to a specific ordering implemented in derived classes.

The iteration step performs the following operations:

  1. Check if the iteration is finished by calling method is_finished() and raises StopIteration if it it is the case

  2. Get the next unseen revision by calling method get_next_rev_id()

  3. Process parents of that revision by calling method process_parent_revs() for the next iteration steps

  4. Check if the revision should be returned by calling method should_return() and returns it if it is the case

In order to easily instantiate a specific type of revisions walker, it is recommended to use the factory function get_revisions_walker().

Parameters
  • storage (swh.storage.interface.StorageInterface) – instance of swh storage (either local or remote)

  • rev_start (bytes) – a revision identifier

  • max_revs (Optional[int]) – maximum number of revisions to return

  • state (Optional[dict]) – previous state of that revisions walker

abstract process_rev(rev_id)[source]

Abstract method whose purpose is to process a newly visited revision during the walk. Derived classes must implement it according to the desired method to walk across the revisions history (for instance through a dfs on the revisions DAG).

Parameters

rev_id (bytes) – the newly visited revision identifier

abstract get_next_rev_id()[source]

Abstract method whose purpose is to return the next revision during the iteration. Derived classes must implement it according to the desired method to walk across the revisions history.

Returns

A dict describing a revision as returned by swh.storage.interface.StorageInterface.revision_get()

Return type

dict

process_parent_revs(rev)[source]

Process the parents of a revision when it is iterated. The default implementation simply calls process_rev() for each parent revision in the order they are declared.

Parameters

rev (dict) – A dict describing a revision as returned by swh.storage.interface.StorageInterface.revision_get()

should_return(rev)[source]

Filter out a revision to return if needed. Default implementation returns all iterated revisions.

Parameters

rev (dict) – A dict describing a revision as returned by swh.storage.interface.StorageInterface.revision_get()

Returns

Whether to return the revision in the iteration

Return type

bool

is_finished()[source]

Determine if the iteration is finished. This method is called at the beginning of each iteration loop.

Returns

Whether the iteration is finished

Return type

bool

missing_revisions()[source]

Return a set of revision identifiers whose associated data were found missing into the archive content while walking on the revisions graph.

Returns

a set of revision identifiers

Return type

Set[bytes]

is_history_truncated()[source]

Return if the revision history generated so far has been truncated of not. A revision history might end up truncated if some revision data were found missing into the archive content.

Returns

Whether the history got truncated or not

Return type

bool

export_state()[source]

Export the internal state of that revision walker to a dict. Its purpose is to continue the iteration in a pagination context.

Returns

A dict containing the internal state of that revisions walker

Return type

dict

class swh.storage.algos.revisions_walker.CommitterDateRevisionsWalker(storage, rev_start, max_revs=None, state=None)[source]

Bases: swh.storage.algos.revisions_walker.RevisionsWalker

Revisions walker that returns revisions in reverse chronological order according to committer date (same behaviour as git log)

rw_type = 'committer_date'
process_rev(rev_id)[source]

Add the revision to a priority queue according to the committer date.

Parameters

rev_id (bytes) – the newly visited revision identifier

get_next_rev_id()[source]

Return the smallest revision from the priority queue, i.e. the one with highest committer date.

Returns

A dict describing a revision as returned by swh.storage.interface.StorageInterface.revision_get()

Return type

dict

class swh.storage.algos.revisions_walker.BFSRevisionsWalker(*args, **kwargs)[source]

Bases: swh.storage.algos.revisions_walker.RevisionsWalker

Revisions walker that returns revisions in the same order as when performing a breadth-first search on the revisions DAG.

rw_type = 'bfs'
process_rev(rev_id)[source]

Append the revision to a queue.

Parameters

rev_id (bytes) – the newly visited revision identifier

get_next_rev_id()[source]

Return the next revision from the queue.

Returns

A dict describing a revision as returned by swh.storage.interface.StorageInterface.revision_get()

Return type

dict

class swh.storage.algos.revisions_walker.DFSPostRevisionsWalker(storage, rev_start, max_revs=None, state=None)[source]

Bases: swh.storage.algos.revisions_walker.RevisionsWalker

Revisions walker that returns revisions in the same order as when performing a depth-first search in post-order on the revisions DAG (i.e. after visiting a merge commit, the merged commit will be visited before the base it was merged on).

rw_type = 'dfs_post'
process_rev(rev_id)[source]

Append the revision to a stack.

Parameters

rev_id (bytes) – the newly visited revision identifier

get_next_rev_id()[source]

Return the next revision from the stack.

Returns

A dict describing a revision as returned by swh.storage.interface.StorageInterface.revision_get()

Return type

dict

class swh.storage.algos.revisions_walker.DFSRevisionsWalker(storage, rev_start, max_revs=None, state=None)[source]

Bases: swh.storage.algos.revisions_walker.DFSPostRevisionsWalker

Revisions walker that returns revisions in the same order as when performing a depth-first search in pre-order on the revisions DAG (i.e. after visiting a merge commit, the base commit it was merged on will be visited before the merged commit).

rw_type = 'dfs'
process_parent_revs(rev)[source]

Process the parents of a revision when it is iterated in the reversed order they are declared.

Parameters

rev (dict) – A dict describing a revision as returned by swh.storage.interface.StorageInterface.revision_get()

class swh.storage.algos.revisions_walker.PathRevisionsWalker(storage, rev_start, path, **kwargs)[source]

Bases: swh.storage.algos.revisions_walker.CommitterDateRevisionsWalker

Revisions walker that returns revisions where a specific path in the source tree has been modified, in other terms it allows to get the history for a specific file or directory.

It has a behaviour similar to what git log offers by default, meaning the returned history is simplified in order to only show relevant revisions (see the History Simplification section of the associated manual for more details).

Please note that to avoid walking the entire history, the iteration will stop once a revision where the path has been added is found.

Warning

Due to client-side implementation, performances are not optimal when the total numbers of revisions to walk is large. This should only be used when the total number of revisions does not exceed a couple of thousands.

Parameters
  • storage (swh.storage.interface.StorageInterface) – instance of swh storage (either local or remote)

  • rev_start (bytes) – a revision identifier

  • path (str) – the path in the source tree to retrieve the history

  • max_revs (Optional[int]) – maximum number of revisions to return

  • state (Optional[dict]) – previous state of that revisions walker

rw_type = 'path'
is_finished()[source]

Check if the revisions iteration is finished. This checks for the specified path’s existence in the last returned revision’s parents’ source trees. If not, the iteration is considered finished.

Returns

Whether to return the revision in the iteration

Return type

bool

process_parent_revs(rev)[source]

Process parents when a new revision is iterated. It enables to get a simplified revisions history in the same manner as git log. When a revision has multiple parents, the following process is applied. If the revision was a merge, and has the same path identifier to one parent, follow only that parent (even if there are several parents with the same path identifier, follow only one of them.) Otherwise, follow all parents.

Parameters

rev (dict) – A dict describing a revision as returned by swh.storage.interface.StorageInterface.revision_get()

should_return(rev)[source]

Check if a revision should be returned when iterating. It verifies that the specified path has been modified by the revision but also that all parents have a path identifier different from the revision one in order to get a simplified history.

Parameters

rev (dict) – A dict describing a revision as returned by swh.storage.interface.StorageInterface.revision_get()

Returns

Whether to return the revision in the iteration

Return type

bool

swh.storage.algos.revisions_walker.get_revisions_walker(rev_walker_type, *args, **kwargs)[source]

Instantiate a revisions walker of a given type.

The following code snippet demonstrates how to use a revisions walker for processing a whole revisions history:

from swh.storage import get_storage

storage = get_storage(...)

revs_walker = get_revisions_walker('committer_date', storage, rev_id)
for rev in revs_walker:
    # process revision rev

It is also possible to walk a revisions history in a paginated way as illustrated below:

def get_revs_history_page(rw_type, storage, rev_id, page_num,
                          page_size, rw_state):
    max_revs = (page_num + 1) * page_size
    revs_walker = get_revisions_walker(rw_type, storage, rev_id,
                                       max_revs=max_revs,
                                       state=rw_state)
    revs = list(revs_walker)
    rw_state = revs_walker.export_state()
    return revs

rev_start = ...
per_page = 50
rw_state = {}

for page in range(0, 10):
    revs_page = get_revs_history_page('dfs', storage, rev_start, page,
                                      per_page, rw_state)
    # process revisions page
Parameters
  • rev_walker_type (str) – the type of revisions walker to return, possible values are: committer_date, dfs, dfs_post, bfs and path

  • args (list) – position arguments to pass to the revisions walker constructor

  • kwargs (dict) – keyword arguments to pass to the revisions walker constructor