45 lines
2.8 KiB
Text
45 lines
2.8 KiB
Text
* Phase 1: Minimum viable product (in order of priority)
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* configurable TOP_LEVEL size
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* test new snappy compression support
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* status and statistics
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* for each level {#merges, {merge-time-min, max, average}}
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* add @doc strings and and -spec's
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* check to make sure every error returns with a reason {error, Reason}
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* Phase 2: Production Ready
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* dual-nursery
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* cache for read-path
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* {cache, bytes(), name} share max(bytes) cache named 'name' via etc
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* snapshot entire database (fresh directory w/ hard links to all files)
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* persist merge progress (to speed up re-opening a HanoiDB)
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* support for future file format changes
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* Define a standard struct which is the metadata added at the end of the
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file, e.g. [btree-nodes] [meta-data] [offset of meta-data]. This is written
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in hanoi_writer:flush_nodes, and read in hanoi_reader:open2.
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* Phase 3: Wish List
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* add truncate/1 - quickly truncates a database to 0 items
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* count/1 - return number of items currently in tree
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* adaptive nursery sizing
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* backpressure on fold operations
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- The "sync_fold" creates a snapshot (hard link to btree files), which
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provides consistent behavior but may use a lot of disk space if there is
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a lot of insertion going on.
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- The "async_fold" folds a limited number, and remembers the last key
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serviced, then picks up from there again. So you could see intermittent
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puts in a subsequent batch of results.
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* add block-level encryption support
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## NOTES:
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1: make the "first level" have more thatn 2^5 entries (controlled by the constant TOP_LEVEL in hanoi.hrl); this means a new set of files is opened/closed/merged for every 32 insert/updates/deletes. Setting this higher will just make the nursery correspondingly larger, which should be absolutely fine.
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2: Right now, the streaming btree writer emits a btree page based on number of elements. This could be changed to be based on the size of the node (say, some block-size boudary) and then add padding at the end so that each node read becomes a clean block transfer. Right now, we're probably taking way to many reads.
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3: Also, there is no caching of read nodes. So every time a btree node is visited it is also read from disk and term_to_binary'ed. But we need a caching system for that to work well (https://github.com/cliffmoon/cherly is difficult to build), it needs to be rebar-ified.
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4: Also, the format for btree nodes could probably be optimized. Right now it's just binary_to_term of a key/value list as far as I remember. Perhaps we dont have to deserialize the entire thing.
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5: It might also be good to employ a scheduler (github.com/esl/jobs<http://github.com/esl/jobs>) for issuing merges; because I think that it can be a problem for the OS if there are too many merges going on at the same time.
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