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![Patrick Steinhardt](/assets/img/avatar_default.png)
When queueing references in git-rev-list(1), we try to optimize parsing of commits via the commit-graph. To do so, we first look up the object's type, and if it is a commit we call `repo_parse_commit()` instead of `parse_object()`. This is quite inefficient though given that we're always uncompressing the object header in order to determine the type. Instead, we can opportunistically search the commit-graph for the object ID: in case it's found, we know it's a commit and can directly fill in the commit object without having to uncompress the object header. Expose a new function `lookup_commit_in_graph()`, which tries to find a commit in the commit-graph by ID, and convert `get_reference()` to use this function. This provides a big performance win in cases where we load references in a repository with lots of references pointing to commits. The following has been executed in a real-world repository with about 2.2 million refs: Benchmark #1: HEAD~: rev-list --unsorted-input --objects --quiet --not --all --not $newrev Time (mean ± σ): 4.458 s ± 0.044 s [User: 4.115 s, System: 0.342 s] Range (min … max): 4.409 s … 4.534 s 10 runs Benchmark #2: HEAD: rev-list --unsorted-input --objects --quiet --not --all --not $newrev Time (mean ± σ): 3.089 s ± 0.015 s [User: 2.768 s, System: 0.321 s] Range (min … max): 3.061 s … 3.105 s 10 runs Summary 'HEAD: rev-list --unsorted-input --objects --quiet --not --all --not $newrev' ran 1.44 ± 0.02 times faster than 'HEAD~: rev-list --unsorted-input --objects --quiet --not --all --not $newrev' Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
174 lines
5.4 KiB
C
174 lines
5.4 KiB
C
#ifndef COMMIT_GRAPH_H
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#define COMMIT_GRAPH_H
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#include "git-compat-util.h"
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#include "object-store.h"
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#include "oidset.h"
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#define GIT_TEST_COMMIT_GRAPH "GIT_TEST_COMMIT_GRAPH"
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#define GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE "GIT_TEST_COMMIT_GRAPH_DIE_ON_PARSE"
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#define GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS "GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS"
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/*
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* This method is only used to enhance coverage of the commit-graph
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* feature in the test suite with the GIT_TEST_COMMIT_GRAPH and
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* GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS environment variables. Do not
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* call this method oustide of a builtin, and only if you know what
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* you are doing!
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*/
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void git_test_write_commit_graph_or_die(void);
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struct commit;
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struct bloom_filter_settings;
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struct repository;
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struct raw_object_store;
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struct string_list;
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char *get_commit_graph_filename(struct object_directory *odb);
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char *get_commit_graph_chain_filename(struct object_directory *odb);
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int open_commit_graph(const char *graph_file, int *fd, struct stat *st);
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/*
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* Given a commit struct, try to fill the commit struct info, including:
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* 1. tree object
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* 2. date
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* 3. parents.
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*
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* Returns 1 if and only if the commit was found in the packed graph.
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*
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* See parse_commit_buffer() for the fallback after this call.
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*/
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int parse_commit_in_graph(struct repository *r, struct commit *item);
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/*
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* Look up the given commit ID in the commit-graph. This will only return a
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* commit if the ID exists both in the graph and in the object database such
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* that we don't return commits whose object has been pruned. Otherwise, this
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* function returns `NULL`.
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*/
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struct commit *lookup_commit_in_graph(struct repository *repo, const struct object_id *id);
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/*
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* It is possible that we loaded commit contents from the commit buffer,
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* but we also want to ensure the commit-graph content is correctly
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* checked and filled. Fill the graph_pos and generation members of
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* the given commit.
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*/
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void load_commit_graph_info(struct repository *r, struct commit *item);
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struct tree *get_commit_tree_in_graph(struct repository *r,
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const struct commit *c);
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struct commit_graph {
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const unsigned char *data;
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size_t data_len;
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unsigned char hash_len;
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unsigned char num_chunks;
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uint32_t num_commits;
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struct object_id oid;
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char *filename;
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struct object_directory *odb;
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uint32_t num_commits_in_base;
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unsigned int read_generation_data;
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struct commit_graph *base_graph;
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const uint32_t *chunk_oid_fanout;
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const unsigned char *chunk_oid_lookup;
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const unsigned char *chunk_commit_data;
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const unsigned char *chunk_generation_data;
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const unsigned char *chunk_generation_data_overflow;
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const unsigned char *chunk_extra_edges;
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const unsigned char *chunk_base_graphs;
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const unsigned char *chunk_bloom_indexes;
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const unsigned char *chunk_bloom_data;
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struct topo_level_slab *topo_levels;
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struct bloom_filter_settings *bloom_filter_settings;
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};
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struct commit_graph *load_commit_graph_one_fd_st(struct repository *r,
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int fd, struct stat *st,
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struct object_directory *odb);
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struct commit_graph *read_commit_graph_one(struct repository *r,
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struct object_directory *odb);
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struct commit_graph *parse_commit_graph(struct repository *r,
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void *graph_map, size_t graph_size);
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/*
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* Return 1 if and only if the repository has a commit-graph
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* file and generation numbers are computed in that file.
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*/
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int generation_numbers_enabled(struct repository *r);
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/*
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* Return 1 if and only if the repository has a commit-graph
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* file and generation data chunk has been written for the file.
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*/
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int corrected_commit_dates_enabled(struct repository *r);
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struct bloom_filter_settings *get_bloom_filter_settings(struct repository *r);
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enum commit_graph_write_flags {
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COMMIT_GRAPH_WRITE_APPEND = (1 << 0),
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COMMIT_GRAPH_WRITE_PROGRESS = (1 << 1),
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COMMIT_GRAPH_WRITE_SPLIT = (1 << 2),
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COMMIT_GRAPH_WRITE_BLOOM_FILTERS = (1 << 3),
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COMMIT_GRAPH_NO_WRITE_BLOOM_FILTERS = (1 << 4),
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};
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enum commit_graph_split_flags {
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COMMIT_GRAPH_SPLIT_UNSPECIFIED = 0,
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COMMIT_GRAPH_SPLIT_MERGE_PROHIBITED = 1,
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COMMIT_GRAPH_SPLIT_REPLACE = 2
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};
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struct commit_graph_opts {
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int size_multiple;
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int max_commits;
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timestamp_t expire_time;
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enum commit_graph_split_flags split_flags;
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int max_new_filters;
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};
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/*
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* The write_commit_graph* methods return zero on success
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* and a negative value on failure. Note that if the repository
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* is not compatible with the commit-graph feature, then the
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* methods will return 0 without writing a commit-graph.
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*/
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int write_commit_graph_reachable(struct object_directory *odb,
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enum commit_graph_write_flags flags,
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const struct commit_graph_opts *opts);
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int write_commit_graph(struct object_directory *odb,
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struct string_list *pack_indexes,
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struct oidset *commits,
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enum commit_graph_write_flags flags,
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const struct commit_graph_opts *opts);
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#define COMMIT_GRAPH_VERIFY_SHALLOW (1 << 0)
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int verify_commit_graph(struct repository *r, struct commit_graph *g, int flags);
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void close_commit_graph(struct raw_object_store *);
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void free_commit_graph(struct commit_graph *);
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/*
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* Disable further use of the commit graph in this process when parsing a
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* "struct commit".
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*/
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void disable_commit_graph(struct repository *r);
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struct commit_graph_data {
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uint32_t graph_pos;
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timestamp_t generation;
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};
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/*
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* Commits should be parsed before accessing generation, graph positions.
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*/
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timestamp_t commit_graph_generation(const struct commit *);
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uint32_t commit_graph_position(const struct commit *);
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#endif
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