view tests/test-glog-topological.t @ 49622:dcb2581e33be stable

memory-usage: fix `hg log --follow --rev R F` space complexity

When running `hg log --follow --rev REVS FILES`, the log code will walk the
history of all FILES starting from the file revisions that exists in each REVS.

Before doing so, it looks if the files actually exists in the target revisions.
To do so, it opens the manifest of each revision in REVS to look up if we find
the associated items in FILES.

Before this changeset this was done in a way that created a changectx for
each target revision, keeping them in memory while we look into each file.

If the set of REVS is large, this means keeping the manifest for each entry in
REVS in memory. That can be large… if REV is in the form `::X`, this can quickly
become huge and saturate the memory. We have seen usage allocating 2GB per
second until memory runs out.

So this changeset invert the two loop so that only one revision is kept in
memory during the operation. This solve the memory explosion issue.

This test file aims at test topological iteration and the various configuration it can has.

  $ cat >> $HGRCPATH << EOF
  > [command-templates]
  > log={rev}\n
  > EOF

On this simple example, all topological branch are displayed in turn until we
can finally display 0. this implies skipping from 8 to 3 and coming back to 7
later.

  $ hg init test01
  $ cd test01
  $ hg unbundle $TESTDIR/bundles/remote.hg
  adding changesets
  adding manifests
  adding file changes
  added 9 changesets with 7 changes to 4 files (+1 heads)
  new changesets bfaf4b5cbf01:916f1afdef90 (9 drafts)
  (run 'hg heads' to see heads, 'hg merge' to merge)

  $ hg log -G
  o  8
  |
  | o  7
  | |
  | o  6
  | |
  | o  5
  | |
  | o  4
  | |
  o |  3
  | |
  o |  2
  | |
  o |  1
  |/
  o  0
  

(display all nodes)

  $ hg log -G -r 'sort(all(), topo)'
  o  8
  |
  o  3
  |
  o  2
  |
  o  1
  |
  | o  7
  | |
  | o  6
  | |
  | o  5
  | |
  | o  4
  |/
  o  0
  

(display nodes filtered by log options)

  $ hg log -G -r 'sort(all(), topo)' -k '.3'
  o  8
  |
  o  3
  |
  ~
  o  7
  |
  o  6
  |
  ~

(revset skipping nodes)

  $ hg log -G --rev 'sort(not (2+6), topo)'
  o  8
  |
  o  3
  :
  o  1
  |
  | o  7
  | :
  | o  5
  | |
  | o  4
  |/
  o  0
  

(begin) from the other branch

  $ hg log -G -r 'sort(all(), topo, topo.firstbranch=5)'
  o  7
  |
  o  6
  |
  o  5
  |
  o  4
  |
  | o  8
  | |
  | o  3
  | |
  | o  2
  | |
  | o  1
  |/
  o  0
  

Topological sort can be turned on via config

  $ cat >> $HGRCPATH << EOF
  > [experimental]
  > log.topo=true
  > EOF

  $ hg log -G
  o  8
  |
  o  3
  |
  o  2
  |
  o  1
  |
  | o  7
  | |
  | o  6
  | |
  | o  5
  | |
  | o  4
  |/
  o  0
  
Does not affect non-graph log
  $ hg log -T '{rev}\n'
  8
  7
  6
  5
  4
  3
  2
  1
  0