Fix incorrect cache eviction #182
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Fix the bug where the fileio cache layer allows read of a evicted cache_block. The cache eviction relies on the evicting thread being the only holder of the cache_block. However, the union_fstream took an optimization to directly grab the underlying input stream of a cache_stream, thus giving up the cahce_block handle, allowing eviction to happen. The fix is to remember the orignal cachestream which holds reference to the cache_block. This prevents the block from being evicted.
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Build failed on python3.4 due to unrelated error in the change in groupby_aggregate test. OK to merge? |
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Fix the bug where the fileio cache layer allows read of a
evicted cache_block.
The cache eviction relies on the evicting thread being the only
holder of the cache_block. However, the union_fstream took an optimization
to directly grab the underlying input stream of a cache_stream,
thus giving up the cahce_block handle, allowing eviction to happen.
The fix is to remember the orignal cachestream which holds reference to
the cache_block. This prevents the block from being evicted.