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From: Jonathan Tan <jonathantanmy@google.com>
To: git@vger.kernel.org
Cc: Jonathan Tan <jonathantanmy@google.com>, gitster@pobox.com
Subject: [PATCH v2 1/4] sha1-file: introduce no-lazy-fetch has_object()
Date: Wed,  5 Aug 2020 16:06:49 -0700	[thread overview]
Message-ID: <f413b34574a330030e08a6eb93ad812975959d7d.1596668156.git.jonathantanmy@google.com> (raw)
In-Reply-To: <cover.1596668156.git.jonathantanmy@google.com>

There have been a few bugs wherein Git fetches missing objects whenever
the existence of an object is checked, even though it does not need to
perform such a fetch. To resolve these bugs, we could look at all the
places that has_object_file() (or a similar function) is used. As a
first step, introduce a new function has_object() that checks for the
existence of an object, with a default behavior of not fetching if the
object is missing and the repository is a partial clone. As we verify
each has_object_file() (or similar) usage, we can replace it with
has_object(), and we will know that we are done when we can delete
has_object_file() (and the other similar functions).

Also, the new function has_object() has more appropriate defaults:
besides not fetching, it also does not recheck packed storage.

Signed-off-by: Jonathan Tan <jonathantanmy@google.com>
---
 object-store.h | 25 +++++++++++++++++++++++--
 sha1-file.c    | 12 ++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/object-store.h b/object-store.h
index f439d47af8..c4fc9dd74e 100644
--- a/object-store.h
+++ b/object-store.h
@@ -239,12 +239,33 @@ int read_loose_object(const char *path,
 		      unsigned long *size,
 		      void **contents);
 
+/* Retry packed storage after checking packed and loose storage */
+#define HAS_OBJECT_RECHECK_PACKED 1
+
+/*
+ * Returns 1 if the object exists. This function will not lazily fetch objects
+ * in a partial clone.
+ */
+int has_object(struct repository *r, const struct object_id *oid,
+	       unsigned flags);
+
+/*
+ * These macros and functions are deprecated. If checking existence for an
+ * object that is likely to be missing and/or whose absence is relatively
+ * inconsequential (or is consequential but the caller is prepared to handle
+ * it), use has_object(), which has better defaults (no lazy fetch in a partial
+ * clone and no rechecking of packed storage). In the unlikely event that a
+ * caller needs to assert existence of an object that it fully expects to
+ * exist, and wants to trigger a lazy fetch in a partial clone, use
+ * oid_object_info_extended() with a NULL struct object_info.
+ *
+ * These functions can be removed once all callers have migrated to
+ * has_object() and/or oid_object_info_extended().
+ */
 #ifndef NO_THE_REPOSITORY_COMPATIBILITY_MACROS
 #define has_sha1_file_with_flags(sha1, flags) repo_has_sha1_file_with_flags(the_repository, sha1, flags)
 #define has_sha1_file(sha1) repo_has_sha1_file(the_repository, sha1)
 #endif
-
-/* Same as the above, except for struct object_id. */
 int repo_has_object_file(struct repository *r, const struct object_id *oid);
 int repo_has_object_file_with_flags(struct repository *r,
 				    const struct object_id *oid, int flags);
diff --git a/sha1-file.c b/sha1-file.c
index ccd34dd9e8..ff444d7abb 100644
--- a/sha1-file.c
+++ b/sha1-file.c
@@ -1988,6 +1988,18 @@ int force_object_loose(const struct object_id *oid, time_t mtime)
 	return ret;
 }
 
+int has_object(struct repository *r, const struct object_id *oid,
+	       unsigned flags)
+{
+	int quick = !(flags & HAS_OBJECT_RECHECK_PACKED);
+	unsigned object_info_flags = OBJECT_INFO_SKIP_FETCH_OBJECT |
+		(quick ? OBJECT_INFO_QUICK : 0);
+
+	if (!startup_info->have_repository)
+		return 0;
+	return oid_object_info_extended(r, oid, NULL, object_info_flags) >= 0;
+}
+
 int repo_has_object_file_with_flags(struct repository *r,
 				    const struct object_id *oid, int flags)
 {
-- 
2.28.0.236.gb10cc79966-goog


  reply	other threads:[~2020-08-05 23:07 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-28  1:04 [PATCH] apply: do not fetch when checking object existence Jonathan Tan
2020-07-28  1:19 ` Junio C Hamano
2020-07-28 18:23   ` Jonathan Tan
2020-08-05 23:06 ` [PATCH v2 0/4] No-lazy-fetch has_object() and some fixes Jonathan Tan
2020-08-05 23:06   ` Jonathan Tan [this message]
2020-08-05 23:06   ` [PATCH v2 2/4] apply: do not lazy fetch when applying binary Jonathan Tan
2020-08-05 23:06   ` [PATCH v2 3/4] pack-objects: no fetch when allow-{any,promisor} Jonathan Tan
2020-08-05 23:06   ` [PATCH v2 4/4] fsck: do not lazy fetch known non-promisor object Jonathan Tan
2020-08-06 20:00   ` [PATCH v2 0/4] No-lazy-fetch has_object() and some fixes Junio C Hamano

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