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As the code is written today index_bulk_checkin only accepts blobs. Remove the enum object_type parameter and rename index_bulk_checkin to index_blob_bulk_checkin, index_stream to index_blob_stream, deflate_to_pack to deflate_blob_to_pack, stream_to_pack to stream_blob_to_pack, to make this explicit. Not supporting commits, tags, or trees has no downside as it is not currently supported now, and commits, tags, and trees being smaller by design do not have the problem that the problem that index_bulk_checkin was built to solve. Before we start adding code to support the hash function transition supporting additional objects types in index_bulk_checkin has no real additional cost, just an extra function parameter to know what the object type is. Once we begin the hash function transition this is not the case. The hash function transition document specifies that a repository with compatObjectFormat enabled will compute and store both the SHA-1 and SHA-256 hash of every object in the repository. What makes this a challenge is that it is not just an additional hash over the same object. Instead the hash function transition document specifies that the compatibility hash (specified with compatObjectFormat) be computed over the equivalent object that another git repository whose storage hash (specified with objectFormat) would store. When comparing equivalent repositories built with different storage hash functions, the oids embedded in objects used to refer to other objects differ and the location of signatures within objects differ. As blob objects have neither oids referring to other objects nor stored signatures their storage hash and their compatibility hash are computed over the same object. The other kinds of objects: trees, commits, and tags, all store oids referring to other objects. Signatures are stored in commit and tag objects. As oids and the tags to store signatures are not the same size in repositories built with different storage hashes the size of the equivalent objects are also different. A version of index_bulk_checkin that supports more than just blobs when computing both the SHA-1 and the SHA-256 of every object added would need a different, and more expensive structure. The structure is more expensive because it would be required to temporarily buffering the equivalent object the compatibility hash needs to be computed over. A temporary object is needed, because before a hash over an object can computed it's object header needs to be computed. One of the members of the object header is the entire size of the object. To know the size of an equivalent object an entire pass over the original object needs to be made, as trees, commits, and tags are composed of a variable number of variable sized pieces. Unfortunately there is no formula to compute the size of an equivalent object from just the size of the original object. Avoid all of those future complications by limiting index_bulk_checkin to only work on blobs. Inspired-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
39 lines
1 KiB
C
39 lines
1 KiB
C
/*
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* Copyright (c) 2011, Google Inc.
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*/
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#ifndef BULK_CHECKIN_H
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#define BULK_CHECKIN_H
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#include "object.h"
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void prepare_loose_object_bulk_checkin(void);
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void fsync_loose_object_bulk_checkin(int fd, const char *filename);
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int index_blob_bulk_checkin(struct object_id *oid,
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int fd, size_t size,
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const char *path, unsigned flags);
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/*
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* Tell the object database to optimize for adding
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* multiple objects. end_odb_transaction must be called
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* to make new objects visible. Transactions can be nested,
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* and objects are only visible after the outermost transaction
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* is complete or the transaction is flushed.
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*/
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void begin_odb_transaction(void);
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/*
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* Make any objects that are currently part of a pending object
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* database transaction visible. It is valid to call this function
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* even if no transaction is active.
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*/
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void flush_odb_transaction(void);
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/*
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* Tell the object database to make any objects from the
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* current transaction visible if this is the final nested
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* transaction.
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*/
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void end_odb_transaction(void);
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#endif
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