VolatileReadData #203
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VolatileReadData #203
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...because we will need the LazyReadData name for the ReadData that wraps LazyRead.
VolatileReadData is Closable. LazyRead is now also Closable. The VolatileReadData implementation LazyReadData closes its delegate LazyRead when it is closed. The file-system FileLazyRead locks the path it refers to on construction and holds the lock until it is closed (via a wrapping LazyReadData). All usages of KVA.createReadData have been revised to use try-with-resources to make sure VolatileReadData are properly closed. DefaultDatasetAccess has been revised to not eagerly materialize ReadData. This is in preparation of using partial loading and prefetching. (This is a separate topic, not necessary for using VolatileReadData correctly, but was too difficult to disentangle in the git history after the fact...)
* add a few tests
* test a list of nulls is returned for non-existing blocks * test number of backend read calls for readBlocks
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We should address this before merging (#204 ) |
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The
ReadDatareturned byKeyValueAccess.createReadDataare nowClosableVolatileReadData.For
FileSystemKeyValueAccess, theVolatileReadDataholds a (read) lock onto its underlyingFileChanneluntil it is closed. All usages ofKeyValueAccess.createReadDatahave been revised to use try-with-resources to make sure allVolatileReadDataare properly closed after use.The
LazyReadinterface has moved to its own file and is now also responsible for implementing theReadData.prefetchfunctionality (optional, currently does nothing).The
ReadDataimplementation that wrapsLazyReadis now namedLazyReadData(instead ofKeyValueAccessReadData) and was moved to thereaddatapackage.There was a previous
LazyReadDataclass that is now calledLazyGeneratedReadData(and it is fed by aReadData.Generatorinstead of aReadData.OutputStreamWritert).The new
LazyReadDataimplementsVolatileReadDataand forwardsclose()to its delegateLazyReadIn
DefaultDatasetAccess, we avoid preemptively materializingReadDatato check whether a given key exists. Instead, we work with theVolatileReadDataand appropriately handleN5NoSuchKeyExceptionwhen this is (later) thrown when working withLazyReadDatafor non-existing keys.We also make sure to materialize
modifiedReadDataeverywhere if write-locks would overlap withexistingReadDatalocks.