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Updated todo list.

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Gregory Burd 2013-05-02 08:41:44 -04:00
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README.md
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`wterl` is an Erlang interface to the WiredTiger database, and is written
to support a Riak storage backend that uses WiredTiger.
This backend currently supports only key-value storage and retrieval.
`wterl` is an Erlang interface to the WiredTiger database, and is written to
support a Riak storage backend that uses WiredTiger.
Remaining work includes:
* The `wterl:session_create` function currently returns an error under
certain circumstances, so we currently ignore its return value.
* The `riak_kv_wterl_backend` module is currently designed to rely on the
fact that it runs in just a single Erlang scheduler thread, which is
necessary because WiredTiger doesn't allow a session to be used
concurrently by different threads. If the KV node design ever changes to
involve concurrency across scheduler threads, this current design will no
longer work correctly.
TODO:
* Find/fix any code marked "TODO:"
* Why do we see {error, {eperm, _}} result on wterl:cursor_close/1 during
fold_objects/4?
* Why do we see {error, {eperm, _}} result on wterl:cursor_close/1?
* Why do we see {error, {eperm, _}} result on wterl:cursor_next/1 during
is_empty/1?
* Why do we see {error, {eperm, _}} result on wterl:cursor_next_value/1
during status/1?
* Why do we see {error, {ebusy, _}} result on wterl:drop/2?
* Determine a better way to estimate the number of sessions we should
configure WT for at startup in riak_kv_wterl_backend:max_sessions/1.
* Provide a way to configure the cursor options, right now they are
always "raw,overwrite".
* Add support for Riak/KV 2i indexes using the same design pattern
as eLevelDB (in a future version consider alternate schema)
* If an operation using a shared cursor results in a non-normal error
then it should be closed/discarded from the recycled pool
* Cache cursors based on hash(table/config) rather than just table.
* Finish NIF unload/reload functions and test.
* Test an upgrade, include a format/schema/WT change.
* When WT_PANIC is returned first try to unload/reload then driver
and reset all state, if that fails then exit gracefully.
* Currently the `riak_kv_wterl_backend` module is stored in this
repository, but it really belongs in the `riak_kv` repository.
* There are currently some stability issues with WiredTiger that can
sometimes cause errors when restarting KV nodes with non-empty WiredTiger
storage.
* wterl:truncate/5 can segv, and its tests are commented out
* Add async_nif and wterl NIF stats to the results provided by the
stats API
* Longer term ideas/changes to consider:
* More testing, especially pulse/qc
* Riak/KV integration
* Store 2i indexes in separate tables
* Store buckets, in separate tables and keep a <<bucket/key>> index
to ensure that folds across a vnode are easy
* Provide a drop bucket API call
* Support key expirey
* An ets API (like the LevelDB's lets project)
* Use mime-type to inform WT's schema for key value encoding
* Other use cases within Riak
* An AAE driver using WT
* An ability to store the ring file via WT
Future support for secondary indexes requires WiredTiger features that are
under development but are not yet available.
Deploying
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