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From: Michael Haggerty <mhagger@alum.mit.edu>
To: Junio C Hamano <gitster@pobox.com>
Cc: Kim Gybels <kgybels@infogroep.be>,
	Johannes Schindelin <johannes.schindelin@gmx.de>,
	Jeff King <peff@peff.net>,
	git@vger.kernel.org, Michael Haggerty <mhagger@alum.mit.edu>
Subject: [PATCH 4/6] packed_ref_iterator_begin(): make optimization more general
Date: Wed, 24 Jan 2018 12:14:14 +0100	[thread overview]
Message-ID: <bf6c0c67430b936738f5e8891b82022d0127acb0.1516791909.git.mhagger@alum.mit.edu> (raw)
In-Reply-To: <cea5e366-dc95-6f41-6373-f8bbef103561@alum.mit.edu>
In-Reply-To: <cover.1516791909.git.mhagger@alum.mit.edu>

We can return an empty iterator not only if the `packed-refs` file is
missing, but also if it is empty or if there are no references whose
names succeed `prefix`. Optimize away those cases as well by moving
the call to `find_reference_location()` higher in the function and
checking whether the determined start position is the same as
`snapshot->eof`. (This is possible now because the previous commit
made `find_reference_location()` robust against empty snapshots.)

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs/packed-backend.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index 361affd7ad..988c45402b 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -927,7 +927,12 @@ static struct ref_iterator *packed_ref_iterator_begin(
 	 */
 	snapshot = get_snapshot(refs);
 
-	if (!snapshot->buf)
+	if (prefix && *prefix)
+		start = find_reference_location(snapshot, prefix, 0);
+	else
+		start = snapshot->start;
+
+	if (start == snapshot->eof)
 		return empty_ref_iterator_begin();
 
 	iter = xcalloc(1, sizeof(*iter));
@@ -937,11 +942,6 @@ static struct ref_iterator *packed_ref_iterator_begin(
 	iter->snapshot = snapshot;
 	acquire_snapshot(snapshot);
 
-	if (prefix && *prefix)
-		start = find_reference_location(snapshot, prefix, 0);
-	else
-		start = snapshot->start;
-
 	iter->pos = start;
 	iter->eof = snapshot->eof;
 	strbuf_init(&iter->refname_buf, 0);
-- 
2.14.2


  parent reply	other threads:[~2018-01-24 11:14 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-13 16:11 [PATCH] packed_ref_cache: don't use mmap() for small files Kim Gybels
2018-01-13 18:56 ` Johannes Schindelin
2018-01-14 19:14 ` [PATCH v2] " Kim Gybels
2018-01-15 12:17   ` [PATCH 0/3] Supplements to "packed_ref_cache: don't use mmap() for small files" Michael Haggerty
2018-01-15 12:17     ` [PATCH 1/3] SQUASH? Mention that `snapshot::buf` can be NULL for empty files Michael Haggerty
2018-01-15 12:17     ` [PATCH 2/3] create_snapshot(): exit early if the file was empty Michael Haggerty
2018-01-15 12:17     ` [PATCH 3/3] find_reference_location(): don't invoke if `snapshot->buf` is NULL Michael Haggerty
2018-01-17 20:23     ` [PATCH 0/3] Supplements to "packed_ref_cache: don't use mmap() for small files" Johannes Schindelin
2018-01-17 21:52     ` Junio C Hamano
2018-01-15 21:15 ` [PATCH] packed_ref_cache: don't use mmap() for small files Jeff King
2018-01-15 23:37   ` Kim Gybels
2018-01-15 23:52     ` Jeff King
2018-01-16 19:38       ` [PATCH v3] " Kim Gybels
2018-01-17 22:09         ` Jeff King
2018-01-21  4:41           ` Michael Haggerty
2018-01-22 19:31             ` Junio C Hamano
2018-01-24 11:05               ` Michael Haggerty
2018-01-24 11:14                 ` [PATCH 0/6] Yet another approach to handling empty snapshots Michael Haggerty
2018-01-24 11:14                   ` [PATCH 1/6] struct snapshot: store `start` rather than `header_len` Michael Haggerty
2018-01-24 20:36                     ` Jeff King
2018-01-24 11:14                   ` [PATCH 2/6] create_snapshot(): use `xmemdupz()` rather than a strbuf Michael Haggerty
2018-01-24 11:14                   ` [PATCH 3/6] find_reference_location(): make function safe for empty snapshots Michael Haggerty
2018-01-24 20:27                     ` Jeff King
2018-01-24 21:11                       ` Junio C Hamano
2018-01-24 21:34                         ` Jeff King
2018-01-24 11:14                   ` Michael Haggerty [this message]
2018-01-24 20:32                     ` [PATCH 4/6] packed_ref_iterator_begin(): make optimization more general Jeff King
2018-01-24 11:14                   ` [PATCH 5/6] load_contents(): don't try to mmap an empty file Michael Haggerty
2018-01-24 11:14                   ` [PATCH 6/6] packed_ref_cache: don't use mmap() for small files Michael Haggerty
2018-01-24 20:38                   ` [PATCH 0/6] Yet another approach to handling empty snapshots Jeff King
2018-01-24 20:54                   ` Junio C Hamano
2018-02-15 16:54                   ` Johannes Schindelin
2018-01-24 18:05                 ` [PATCH v3] packed_ref_cache: don't use mmap() for small files Junio C Hamano

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