Commit Graph

5 Commits

Author SHA1 Message Date
Denton Liu
62d58cda69 t1409: use test_path_is_missing()
The test_must_fail() function should only be used for git commands since
we should assume that external commands work sanely. Replace
`test_must_fail test -f` with `test_path_is_missing` since we expect
these paths to not exist.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-12-20 11:30:45 -08:00
Denton Liu
b87b02cfe6 t1409: let sed open its own input file
In one case, we were using a redirection operator to feed input into
sed. However, since sed is capable of opening its own input file, make
sed do that instead of redirecting input into it.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-12-20 11:30:45 -08:00
Denton Liu
f511bc02ed t0020: use ! check_packed_refs_marked
The test_must_fail function should only be used for git commands since
we should assume that external commands work sanely. Since
check_packed_refs_marked() just wraps a grep invocation, replace
`test_must_fail check_packed_refs_marked` with
`! check_packed_refs_marked`.

Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-12-20 11:30:44 -08:00
Michael Haggerty
7c6bd25c7d files-backend: don't rewrite the packed-refs file unnecessarily
Even when we are deleting references, we needn't overwrite the
`packed-refs` file if the references that we are deleting only exist
as loose references. Implement this optimization as follows:

* Add a function `is_packed_transaction_needed()`, which checks
  whether a given packed-refs transaction actually needs to be carried
  out (i.e., it returns false if the transaction obviously wouldn't
  have any effect). This function must be called while holding the
  `packed-refs` lock to avoid races.

* Change `files_transaction_prepare()` to check whether the
  packed-refs transaction is actually needed. If not, squelch it, but
  continue holding the `packed-refs` lock until the end of the
  transaction to avoid races.

This fixes a mild regression caused by dc39e09942 (files_ref_store:
use a transaction to update packed refs, 2017-09-08). Before that
commit, unnecessary rewrites of `packed-refs` were suppressed by
`repack_without_refs()`. But the transaction-based writing introduced
by that commit didn't perform that optimization.

Note that the pre-dc39e09942 code still had to *read* the whole
`packed-refs` file to determine that the rewrite could be skipped, so
the performance for the cases that the write could be elided was
`O(N)` in the number of packed references both before and after
dc39e09942. But after that commit the constant factor increased.

This commit reimplements the optimization of eliding unnecessary
`packed-refs` rewrites. That, plus the fact that since
cfa2e29c34 (packed_ref_store: get rid of the `ref_cache` entirely,
2017-03-17) we don't necessarily have to read the whole `packed-refs`
file at all, means that deletes of one or a few loose references can
now be done with `O(n lg N)` effort, where `n` is the number of loose
references being deleted and `N` is the total number of packed
references.

This commit fixes two tests in t1409.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-30 09:45:15 +09:00
Michael Haggerty
cf79bd9f4c t1409: check that packed-refs is not rewritten unnecessarily
There is no need to rewrite the `packed-refs` file except for the case
that we are deleting a reference that has a packed version. Verify
that `packed-refs` is not rewritten when it shouldn't be.

In fact, two of these tests fail:

* A new (empty) `packed-refs` file is created when deleting any loose
  reference and no `packed-refs` file previously existed.

* The `packed-refs` file is rewritten unnecessarily when deleting a
  loose reference that has no packed counterpart.

Both problems will be fixed in the next commit.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-10-27 10:12:42 +09:00