2017-06-23 07:01:37 +00:00
|
|
|
#ifndef REFS_PACKED_BACKEND_H
|
|
|
|
|
#define REFS_PACKED_BACKEND_H
|
|
|
|
|
|
2018-09-19 00:11:44 +00:00
|
|
|
struct ref_transaction;
|
|
|
|
|
|
2017-09-08 13:51:45 +00:00
|
|
|
/*
|
|
|
|
|
* Support for storing references in a `packed-refs` file.
|
|
|
|
|
*
|
|
|
|
|
* Note that this backend doesn't check for D/F conflicts, because it
|
|
|
|
|
* doesn't care about them. But usually it should be wrapped in a
|
|
|
|
|
* `files_ref_store` that prevents D/F conflicts from being created,
|
|
|
|
|
* even among packed refs.
|
|
|
|
|
*/
|
|
|
|
|
|
2017-06-23 07:01:38 +00:00
|
|
|
struct ref_store *packed_ref_store_create(const char *path,
|
|
|
|
|
unsigned int store_flags);
|
2017-06-23 07:01:37 +00:00
|
|
|
|
|
|
|
|
/*
|
|
|
|
|
* Lock the packed-refs file for writing. Flags is passed to
|
2017-06-23 07:01:42 +00:00
|
|
|
* hold_lock_file_for_update(). Return 0 on success. On errors, write
|
|
|
|
|
* an error message to `err` and return a nonzero value.
|
2017-06-23 07:01:37 +00:00
|
|
|
*/
|
2017-06-23 07:01:42 +00:00
|
|
|
int packed_refs_lock(struct ref_store *ref_store, int flags, struct strbuf *err);
|
2017-06-23 07:01:37 +00:00
|
|
|
|
2017-06-23 07:01:43 +00:00
|
|
|
void packed_refs_unlock(struct ref_store *ref_store);
|
|
|
|
|
int packed_refs_is_locked(struct ref_store *ref_store);
|
|
|
|
|
|
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>
2017-10-28 09:16:02 +00:00
|
|
|
/*
|
|
|
|
|
* Return true if `transaction` really needs to be carried out against
|
|
|
|
|
* the specified packed_ref_store, or false if it can be skipped
|
|
|
|
|
* (i.e., because it is an obvious NOOP). `ref_store` must be locked
|
|
|
|
|
* before calling this function.
|
|
|
|
|
*/
|
|
|
|
|
int is_packed_transaction_needed(struct ref_store *ref_store,
|
|
|
|
|
struct ref_transaction *transaction);
|
|
|
|
|
|
2017-06-23 07:01:37 +00:00
|
|
|
#endif /* REFS_PACKED_BACKEND_H */
|