Mercurial > hg
diff rust/hg-core/src/copy_tracing.rs @ 45944:595979dc924e
copies: introduce a basic Rust function for `combine_changeset_copies`
This new function mirror the python code. This first implementation does a lot
of data copies and is therefore quite slow. However my goal here is to create a
simple "frame" from where to start adding optimization.
This patch focus on the `hg-core` part of this work. Coming patches will do the
necessary `hg-cpython` work to be able to use this from Python.
Differential Revision: https://phab.mercurial-scm.org/D9297
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
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date | Thu, 01 Oct 2020 18:51:06 +0200 |
parents | |
children | 0d99778af68a |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/rust/hg-core/src/copy_tracing.rs Thu Oct 01 18:51:06 2020 +0200 @@ -0,0 +1,262 @@ +use crate::utils::hg_path::HgPathBuf; +use crate::Revision; + +use std::collections::HashMap; +use std::collections::HashSet; + +pub type PathCopies = HashMap<HgPathBuf, HgPathBuf>; + +#[derive(Clone, Debug)] +struct TimeStampedPathCopy { + /// revision at which the copy information was added + rev: Revision, + /// the copy source, (Set to None in case of deletion of the associated + /// key) + path: Option<HgPathBuf>, +} + +/// maps CopyDestination to Copy Source (+ a "timestamp" for the operation) +type TimeStampedPathCopies = HashMap<HgPathBuf, TimeStampedPathCopy>; + +/// hold parent 1, parent 2 and relevant files actions. +pub type RevInfo = (Revision, Revision, ChangedFiles); + +/// represent the files affected by a changesets +/// +/// This hold a subset of mercurial.metadata.ChangingFiles as we do not need +/// all the data categories tracked by it. +pub struct ChangedFiles { + removed: HashSet<HgPathBuf>, + merged: HashSet<HgPathBuf>, + salvaged: HashSet<HgPathBuf>, + copied_from_p1: PathCopies, + copied_from_p2: PathCopies, +} + +impl ChangedFiles { + pub fn new( + removed: HashSet<HgPathBuf>, + merged: HashSet<HgPathBuf>, + salvaged: HashSet<HgPathBuf>, + copied_from_p1: PathCopies, + copied_from_p2: PathCopies, + ) -> Self { + ChangedFiles { + removed, + merged, + salvaged, + copied_from_p1, + copied_from_p2, + } + } + + pub fn new_empty() -> Self { + ChangedFiles { + removed: HashSet::new(), + merged: HashSet::new(), + salvaged: HashSet::new(), + copied_from_p1: PathCopies::new(), + copied_from_p2: PathCopies::new(), + } + } +} + +/// Same as mercurial.copies._combine_changeset_copies, but in Rust. +/// +/// Arguments are: +/// +/// revs: all revisions to be considered +/// children: a {parent ? [childrens]} mapping +/// target_rev: the final revision we are combining copies to +/// rev_info(rev): callback to get revision information: +/// * first parent +/// * second parent +/// * ChangedFiles +/// isancestors(low_rev, high_rev): callback to check if a revision is an +/// ancestor of another +pub fn combine_changeset_copies( + revs: Vec<Revision>, + children: HashMap<Revision, Vec<Revision>>, + target_rev: Revision, + rev_info: &impl Fn(Revision) -> RevInfo, + is_ancestor: &impl Fn(Revision, Revision) -> bool, +) -> PathCopies { + let mut all_copies = HashMap::new(); + + for rev in revs { + // Retrieve data computed in a previous iteration + let copies = all_copies.remove(&rev); + let copies = match copies { + Some(c) => c, + None => TimeStampedPathCopies::default(), // root of the walked set + }; + + let current_children = match children.get(&rev) { + Some(c) => c, + None => panic!("inconsistent `revs` and `children`"), + }; + + for child in current_children { + // We will chain the copies information accumulated for `rev` with + // the individual copies information for each of its children. + // Creating a new PathCopies for each `rev` ? `children` vertex. + let (p1, p2, changes) = rev_info(*child); + + let (parent, child_copies) = if rev == p1 { + (1, &changes.copied_from_p1) + } else { + assert_eq!(rev, p2); + (2, &changes.copied_from_p2) + }; + let mut new_copies = copies.clone(); + + for (dest, source) in child_copies { + let entry; + if let Some(v) = copies.get(source) { + entry = match &v.path { + Some(path) => Some((*(path)).to_owned()), + None => Some(source.to_owned()), + } + } else { + entry = Some(source.to_owned()); + } + // Each new entry is introduced by the children, we record this + // information as we will need it to take the right decision + // when merging conflicting copy information. See + // merge_copies_dict for details. + let ttpc = TimeStampedPathCopy { + rev: *child, + path: entry, + }; + new_copies.insert(dest.to_owned(), ttpc); + } + + // We must drop copy information for removed file. + // + // We need to explicitly record them as dropped to propagate this + // information when merging two TimeStampedPathCopies object. + for f in changes.removed.iter() { + if new_copies.contains_key(f.as_ref()) { + let ttpc = TimeStampedPathCopy { + rev: *child, + path: None, + }; + new_copies.insert(f.to_owned(), ttpc); + } + } + + // Merge has two parents needs to combines their copy information. + // + // If the vertex from the other parent was already processed, we + // will have a value for the child ready to be used. We need to + // grab it and combine it with the one we already + // computed. If not we can simply store the newly + // computed data. The processing happening at + // the time of the second parent will take care of combining the + // two TimeStampedPathCopies instance. + match all_copies.remove(child) { + None => { + all_copies.insert(child, new_copies); + } + Some(other_copies) => { + let (minor, major) = match parent { + 1 => (other_copies, new_copies), + 2 => (new_copies, other_copies), + _ => unreachable!(), + }; + let merged_copies = + merge_copies_dict(minor, major, &changes, is_ancestor); + all_copies.insert(child, merged_copies); + } + }; + } + } + + // Drop internal information (like the timestamp) and return the final + // mapping. + let tt_result = all_copies + .remove(&target_rev) + .expect("target revision was not processed"); + let mut result = PathCopies::default(); + for (dest, tt_source) in tt_result { + if let Some(path) = tt_source.path { + result.insert(dest, path); + } + } + result +} + +/// merge two copies-mapping together, minor and major +/// +/// In case of conflict, value from "major" will be picked, unless in some +/// cases. See inline documentation for details. +#[allow(clippy::if_same_then_else)] +fn merge_copies_dict( + minor: TimeStampedPathCopies, + major: TimeStampedPathCopies, + changes: &ChangedFiles, + is_ancestor: &impl Fn(Revision, Revision) -> bool, +) -> TimeStampedPathCopies { + let mut result = minor.clone(); + for (dest, src_major) in major { + let overwrite; + if let Some(src_minor) = minor.get(&dest) { + if src_major.path == src_minor.path { + // we have the same value, but from other source; + if src_major.rev == src_minor.rev { + // If the two entry are identical, no need to do anything + overwrite = false; + } else if is_ancestor(src_major.rev, src_minor.rev) { + overwrite = false; + } else { + overwrite = true; + } + } else if src_major.rev == src_minor.rev { + // We cannot get copy information for both p1 and p2 in the + // same rev. So this is the same value. + overwrite = false; + } else if src_major.path.is_none() + && changes.salvaged.contains(&dest) + { + // If the file is "deleted" in the major side but was salvaged + // by the merge, we keep the minor side alive + overwrite = false; + } else if src_minor.path.is_none() + && changes.salvaged.contains(&dest) + { + // If the file is "deleted" in the minor side but was salvaged + // by the merge, unconditionnaly preserve the major side. + overwrite = true; + } else if changes.merged.contains(&dest) { + // If the file was actively merged, copy information from each + // side might conflict. The major side will win such conflict. + overwrite = true; + } else if is_ancestor(src_major.rev, src_minor.rev) { + // If the minor side is strictly newer than the major side, it + // should be kept. + overwrite = false; + } else if src_major.path.is_some() { + // without any special case, the "major" value win other the + // "minor" one. + overwrite = true; + } else if is_ancestor(src_minor.rev, src_major.rev) { + // the "major" rev is a direct ancestors of "minor", any + // different value should overwrite + overwrite = true; + } else { + // major version is None (so the file was deleted on that + // branch) annd that branch is independant (neither minor nor + // major is an ancestors of the other one.) We preserve the new + // information about the new file. + overwrite = false; + } + } else { + // minor had no value + overwrite = true; + } + if overwrite { + result.insert(dest, src_major); + } + } + result +}