66 lines
3.8 KiB
Text
66 lines
3.8 KiB
Text
* lsm_btree
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* [cleanup] add @doc strings and and -spec's
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* [cleanup] check to make sure every error returns with a reason {error, Reason}
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* [feature] statistics
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* [feature] use lager for error messages
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* [feature] add config parameters on open
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* {sync, boolean()} fdsync or not on write
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* {cache, bytes(), name} share max(bytes) cache named 'name' via etc
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* [enhancement] use etc/emmap to access/cache files
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* [enhancement] adaptive nursery sizing
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* [feature] support for time based expiry, merge should eliminate expired data
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* [feature] add truncate/1 - quickly truncates a database to 0 items
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* [feature] add sync/1 - flush pending writes to disk (aka checkpoint)
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(nursery:finish() and finish/flush any merges)
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* [feature] count/1 - return number of items currently in tree
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* [feature] "group" commit - ability to make many k/v add/update/deletes atomic (for 2i)
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* [enhancement] 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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* riak_kv_lsm_tree_backend
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* add support for time-based expiry
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* finish support for 2i
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* add stats collection
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- For each level {#merges, {merge-time-min, max, average}}
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PHASE 2:
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* lsm_btree
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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 lsm_btree_writer:flush_nodes, and read in lsm_btree_reader:open2.
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* [feature] compression, encryption on disk
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PHASE 3:
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* lsm_ixdb
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* lsm_{btree, ctrie, ...} support for sub-databases and associations with
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different index types
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* [major change] add more CAPABILITIES such as
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test-and-set(Fun, Key, Value) - to compare a vclock quickly, to speed up
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the get/put patch for every update
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* [enhancement] change encoding/layout of data on disk using sub-databases
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and secondary indexes
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bucket/key{meta[], data} -> ??
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REVIEW LITERATURE AND OTHER SIMILAR IMPLEMENTATAIONS:
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* nessdb https://code.google.com/p/nessdb/source/browse/LSM-BTREE?r=3a1df166a19505a2369dd954e8fc6d0a545f3d7b
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* http://tokutek.com/downloads/mysqluc-2010-fractal-trees.pdf page 14+
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* http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.44.2782&rep=rep1&type=pdf
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1: make the "first level" have more thatn 2^5 entries (controlled by the constant TOP_LEVEL in lsm_btree.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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