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Kirill Smelkov
git-backup
Commits
cc6ac54f
Commit
cc6ac54f
authored
Jun 12, 2018
by
Kirill Smelkov
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pull: TODO on how to avoid O(n^2) on every `git fetch` for references
parent
3efed898
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1
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git-backup.go
git-backup.go
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git-backup.go
View file @
cc6ac54f
...
@@ -493,6 +493,24 @@ func cmd_pull_(gb *git.Repository, pullspecv []PullSpec) {
...
@@ -493,6 +493,24 @@ func cmd_pull_(gb *git.Repository, pullspecv []PullSpec) {
refv
,
_
,
err
:=
fetch
(
path
,
alreadyHave
)
refv
,
_
,
err
:=
fetch
(
path
,
alreadyHave
)
exc
.
Raiseif
(
err
)
exc
.
Raiseif
(
err
)
// TODO don't store to git references all references from fetched repository:
//
// We need to store to git references only references that were actually
// fetched - so that next fetch, e.g. from a fork that also has new data
// as its upstream, won't have to transfer what we just have fetched
// from upstream.
//
// For this purpose we can also save references by naming them as their
// sha1, not actual name, which will automatically deduplicate them in
// between several repositories, especially when/if pull will be made to
// work in parallel.
//
// Such changed-only deduplicated references should be O(δ) - usually only
// a few, and this way we will also automatically avoid O(n^2) behaviour
// of every git fetch scanning all local references at its startup.
//
// For backup.refs, we can generate it directly from refv of all fetched
// repositories saved in RAM.
reporefprefix
:=
backup_refs_work
+
reporefprefix
:=
backup_refs_work
+
// NOTE repo name is escaped as it can contain e.g. spaces, and refs must not
// NOTE repo name is escaped as it can contain e.g. spaces, and refs must not
path_refescape
(
reprefix
(
dir
,
prefix
,
path
))
path_refescape
(
reprefix
(
dir
,
prefix
,
path
))
...
@@ -616,8 +634,8 @@ func cmd_pull_(gb *git.Repository, pullspecv []PullSpec) {
...
@@ -616,8 +634,8 @@ func cmd_pull_(gb *git.Repository, pullspecv []PullSpec) {
// TODO Revisit this when reworking fetch to be parallel. Reason is: in
// TODO Revisit this when reworking fetch to be parallel. Reason is: in
// the process of pulling repositories, the more references we
// the process of pulling repositories, the more references we
// accumulate, the longer pull starts to be, so it becomes O(n^2).
// accumulate, the longer pull starts to be, so it becomes O(n^2).
//
We can avoid quadratic behaviour via removing refs from just
//
//
pulled repo right after the pu
ll.
//
-> what to do is described nearby fetch/mkref ca
ll.
gitdir
:=
xgit
(
"rev-parse"
,
"--git-dir"
)
gitdir
:=
xgit
(
"rev-parse"
,
"--git-dir"
)
err
=
os
.
RemoveAll
(
gitdir
+
"/"
+
backup_refs_work
)
err
=
os
.
RemoveAll
(
gitdir
+
"/"
+
backup_refs_work
)
exc
.
Raiseif
(
err
)
// NOTE err is nil if path does not exist
exc
.
Raiseif
(
err
)
// NOTE err is nil if path does not exist
...
...
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