Jinfeng Ni created DRILL-4589:
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Summary: Reduce planning time for file system partition pruning by
reducing filter evaluation overhead
Key: DRILL-4589
URL: https://issues.apache.org/jira/browse/DRILL-4589
Project: Apache Drill
Issue Type: Bug
Components: Query Planning & Optimization
Reporter: Jinfeng Ni
When Drill is used to query hundreds of thousands, or even millions of files
organized into multi-level directories, user typically will provide a partition
filter like : dir0 = something and dir1 = something2 and .. .
For such queries, we saw the query planning time could be unacceptable long,
due to three main overheads: 1) to expand and get the list of files, 2) to
evaluate the partition filter, 3) to get the metadata, in the case of parquet
files for which metadata cache file is not available.
DRILL-2517 targets at the 3rd part of overhead. As a follow-up work after
DRILL-2517, we plan to reduce the filter evaluation overhead. For now, the
partition filter evaluation is applied to file level. In many cases, we saw
that the number of leaf subdirectories is significantly lower than that of
files. Since all the files under the same leaf subdirecctory share the same
directory metadata, we should apply the filter evaluation at the leaf
subdirectory. By doing that, we could reduce the cpu overhead to evaluate the
filter, and the memory overhead as well.
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