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A platform-agnostic multi-level index for OCaml








  • Update for compatibility with mtime.2.0.0, which is now the lower bounds (#392, @patricoferris)

1.6.1 (2022-06-08)


  • Support all version of cmdliner (#386)


  • Make index-bench's bench executable private, avoiding executable name collisions in opam-monorepo projects. (#389, @NathanReb)

1.6.0 (2022-02-12)


  • Added a Raw.Header_prefix function, for use by libraries that share the file format used by index.unix. (#378)

1.5.0 (2021-11-09)


  • The benchmarks now use tezos-base58 instead of tezos-context-hash (#367)

  • Add an LRU to cache the result of Index.find operations. The default LRU capacity is 30_000 entries. (#366)

1.4.2 (2021-10-15)


  • Fix stats recording in Raw.unsafe_write (#351)


  • Changed the implementation of the write-ahead log to significantly reduce its memory usage (at the cost of some additional disk IO). (#355)

1.4.1 (2021-07-16)


  • Proper cleaning of merge file descriptors when aborting a merge (#326)

  • Recover from crash of the merge thread. When this happen, the main thread can continue to run and will need to recover from the crash before doing a new merge. This fixes a critical issue which might cause data loss (#339)

  • Make sure that no entries can disappear for read-only instances during log_async recovery (#338)

1.4.0 (2021-06-16)


  • Fixed a crash-consistency bug due to a potential flush of an incomplete entry to disk. Entries are now flushed as complete strings. (#301)

  • Attempt to recover from log_async invariant violations during an explicit sync operation, rather than failing immediately. (#329)


  • Release overly defensive warnings occuring when pre-fetching the disk. (#322)

  • Optimised the in-memory representation of index handles and intermediate buffers, resulting in a significant reduction in memory use. (#273, #279)

  • Benches are now executed 3 times and a new option nb-exec has been added (#292)

  • Index.Make now requires an implementation of a monotonic time source. (#321)

  • The Index.Make functor now takes a single Platform argument containing all system dependencies (i.e. IO, Clock, Semaphore and Thread). The Platform module holds the necessary types for these modules. (#321, #330)


  • Added benchmarks that replay a trace of index operations. (#300)

  • Log reporter for the benches

1.3.1 (2021-04-29)


  • Reduce allocations during merge (#274, #277)

  • Protect concurrent syncs with a lock (#309)

  • Fixed a performance issue for Index.sync when there is a blocking merge in progress: the log_async file was not cached properly and fully reloaded from disk every time. (#310)

  • Release the merge lock if a merge raises an exception (#312)

  • Added fsync after Index.clear to signal more quickly to read-only instances than something has changed in the file (#308)


  • Specialise IO.v to create read-only or read-write instances. (#291)

  • clear removes the files on disks and opens new ones containing only the header. (#288, #307, #317)

1.3.0 (2021-01-05)


  • Added flush_callback parameter to the creation of a store, to register a callback before a flush. This callback can be temporarily disabled by ~no_callback:() to flush. (#189, #216)

  • Added Stats.merge_durations to list the duration of the last 10 merges. (#193)

  • Added is_merging to detect if a merge is running. (#192)

  • New IO.Header.{get,set} functions to read and write the file headers atomically (#175, #204, @icristescu, @CraigFe, @samoht)

  • Added a throttle configuration option to select the strategy to use when the cache are full and an async merge is already in progress. The current behavior is the (default) `Block_writes strategy. The new `Overcommit_memory does not block but continue to fill the cache instead. (#209, @samoht)

  • Add IO.exists obligation for IO implementations, to be used for lazy creation of IO instances. (#233, @CraigFe)

  • Index.close now takes an ~immediately:() argument. When passed, this causes close to terminate any ongoing asynchronous merge operation, rather than waiting for it to finish. (#185, #234)

  • Added Index.Checks.cli, which provides offline integrity checking of Index stores. (#236)

  • Index.replace now takes a ~overcommit argument to postpone a merge. (#253)

  • Index.merge is now part of the public API. (#253)

  • Index.try_merge is now part of the public API. try_merge' is a no-op if the number of entries in the write-ahead log is smaller than log_size, otherwise it's merge'. (#253 @samoht)


  • sync has to be called by the read-only instance to synchronise with the files on disk. (#175)

  • Caching of Index instances is now explicit: Index.Make requires a cache implementation, and Index.v may be passed a cache to be used for instance sharing. The default behaviour is not to share instances. (#188)


  • Added values after a clear are found by read-only instances. (#168)

  • Fix a race between merge and sync (#203, @samoht, @CraigFe)

  • Fix a potential loss of data if a crash occurs at the end of a merge (#232)

  • Fix Index.iter to only iterate once over elements persisted on the disk (#260, @samoht, @icristescu)

1.2.1 (2020-06-24)


  • Added Index_unix.Syscalls, a module exposing various Unix bindings for interacting with file-systems. (#176)


  • Fail when Index_unix.IO file version number is not as expected. (#178)

  • Fixed creation of an index when an empty data file exists. (#173)

1.2.0 (2020-02-25)


  • Added filter, removing bindings depending on a predicate (#165)


  • Parameterise Index.Make over arbitrary mutex and thread implementations (and remove the obligation for IO to provide this functionality). (#160, #161)

1.1.0 (2019-12-21)


  • Improve the cooperativeness of the merge operation, allowing concurrent read operations to share CPU resources with ongoing merges. (#152)

  • Improve speed of read operations for read-only instances. (#141)


  • Remove force_merge from Index.S, due to difficulties with guaranteeing sensible semantics to this function under MRSW access patterns. (#147, #150)

1.0.1 (2019-11-29)


  • Provide a better CLI interface for the benchmarks (#130, #133)


  • Fix a segmentation fault when using musl <= 1.1.20 by not allocating 64k-byte buffers on the thread stack (#132)

  • Do not call pwrite with len=0 (#131)

  • Clear log.mem on close (#135)

  • Load log_async on startup (#136)

1.0.0 (2019-11-14)

First stable release.