Weston Pace created ARROW-17599:
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Summary: [C++] ReadRangeCache should not retain data after read
Key: ARROW-17599
URL: https://issues.apache.org/jira/browse/ARROW-17599
Project: Apache Arrow
Issue Type: Improvement
Components: C++
Reporter: Weston Pace
I've added a unit test of the issue here:
https://github.com/westonpace/arrow/tree/experiment/read-range-cache-retention
We use the ReadRangeCache for pre-buffering IPC and parquet files. Sometimes
those files are quite large (gigabytes). The usage is roughly:
for X in num_row_groups:
CacheAllThePiecesWeNeedForRowGroupX
WaitForPiecesToArriveForRowGroupX
ReadThePiecesWeNeedForRowGroupX
However, once we've read in row group X and passed it on to Acero, etc. we do
not release the data for row group X. The read range cache's entries vector
still holds a pointer to the buffer. The data is not released until the file
reader itself is destroyed which only happens when we have finished processing
an entire file.
This leads to excessive memory usage when pre-buffering is enabled.
This could potentially be a little difficult to implement because a single read
range's cache entry could be shared by multiple ranges so we will need some
kind of reference counting to know when we have fully finished with an entry
and can release it.
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