Eric Liang created SPARK-17994:
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Summary: Add back a file status cache for catalog tables
Key: SPARK-17994
URL: https://issues.apache.org/jira/browse/SPARK-17994
Project: Spark
Issue Type: Improvement
Reporter: Eric Liang
In SPARK-16980, we removed the full in-memory cache of table partitions in
favor of loading only needed partitions from the metastore. This greatly
improves the initial latency of queries that only read a small fraction of
table partitions.
However, since the metastore does not store file statistics, we need to
discover those from remote storage. With the loss of the in-memory file status
cache this has to happen on each query, increasing the latency of repeated
queries over the same partitions.
The proposal is to add back a per-table cache of partition contents, i.e.
Map[Path, Array[FileStatus]]. This cache would be retained per-table, and would
be invalidated through refreshTable() and refreshByPath(). Unlike the prior
cache, it can be incrementally updated as new partitions are read.
cc [~michael]
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