comparison rust/hg-core/src/discovery.rs @ 42744:c5748c6969b9

rust-discovery: optimization of add commons/missings for empty arguments

These two cases have to be catched early for different reasons.
In the case of add_missing_revisions, we don't want to trigger
the computation of the undecided set (and the children cache)
too early: the later the better.

In the case of add_common_revisions, the inner `MissingAncestors`
object wouldn't know that all ancestors of its bases have already
been removed from the undecided.
In principle, that would in itself be a lead for further
improvement: this remove_ancestors_from could be more incremental,
but the current performance seems to be good enough.

Differential Revision: https://phab.mercurial-scm.org/D6429

42743:8c9a6adec67a

    /// Register revisions known as being common
    pub fn add_common_revisions(
        &mut self,
        common: impl IntoIterator<Item = Revision>,
    ) -> Result<(), GraphError> {
        self.common.add_bases(common);
        if let Some(ref mut undecided) = self.undecided {
            self.common.remove_ancestors_from(undecided)?;
        }
        Ok(())
    }

    /// caller should avoid calling this too early.
    pub fn add_missing_revisions(
        &mut self,
        missing: impl IntoIterator<Item = Revision>,
    ) -> Result<(), GraphError> {
        self.ensure_children_cache()?;
        self.ensure_undecided()?; // for safety of possible future refactors
        let children = self.children_cache.as_ref().unwrap();
        let mut seen: HashSet<Revision> = HashSet::new();
        let mut tovisit: VecDeque<Revision> = missing.into_iter().collect();
        let undecided_mut = self.undecided.as_mut().unwrap();
        while let Some(rev) = tovisit.pop_front() {
            if !self.missing.insert(rev) {
                // either it's known to be missing from a previous
                // invocation, and there's no need to iterate on its

42744:c5748c6969b9

    /// Register revisions known as being common
    pub fn add_common_revisions(
        &mut self,
        common: impl IntoIterator<Item = Revision>,
    ) -> Result<(), GraphError> {
        let before_len = self.common.get_bases().len();
        self.common.add_bases(common);
        if self.common.get_bases().len() == before_len {
            return Ok(());
        }
        if let Some(ref mut undecided) = self.undecided {
            self.common.remove_ancestors_from(undecided)?;
        }
        Ok(())
    }

    /// caller should avoid calling this too early.
    pub fn add_missing_revisions(
        &mut self,
        missing: impl IntoIterator<Item = Revision>,
    ) -> Result<(), GraphError> {
        let mut tovisit: VecDeque<Revision> = missing.into_iter().collect();
        if tovisit.is_empty() {
            return Ok(());
        }
        self.ensure_children_cache()?;
        self.ensure_undecided()?; // for safety of possible future refactors
        let children = self.children_cache.as_ref().unwrap();
        let mut seen: HashSet<Revision> = HashSet::new();
        let undecided_mut = self.undecided.as_mut().unwrap();
        while let Some(rev) = tovisit.pop_front() {
            if !self.missing.insert(rev) {
                // either it's known to be missing from a previous
                // invocation, and there's no need to iterate on its