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https://issues.apache.org/jira/browse/IMPALA-9228?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Zoltán Borók-Nagy updated IMPALA-9228:
--------------------------------------
Description:
The ORC scanners uses an external library to read ORC files. The library reads
the file contents into its own memory representation. It is a vectorized
representation similar to the Arrow format.
Impala needs to convert the ORC row batch to an Impala row batch. Currently the
conversion happens row-wise via virtual function calls:
[https://github.com/apache/impala/blob/85425b81f04c856d7d5ec375242303f78ec7964e/be/src/exec/hdfs-orc-scanner.cc#L671]
[https://github.com/apache/impala/blob/85425b81f04c856d7d5ec375242303f78ec7964e/be/src/exec/orc-column-readers.cc#L352]
Instead of this approach it could work similarly to the Parquet scanner that
fills the columns one-by-one into a scratch batch, then evaluate the conjuncts
on the scratch batch. For more details see HdfsParquetScanner::AssembleRows():
[https://github.com/apache/impala/blob/85425b81f04c856d7d5ec375242303f78ec7964e/be/src/exec/parquet/hdfs-parquet-scanner.cc#L1077-L1088]
This way we'll need a lot less virtual function calls, also the memory
reads/writes will be much more localized and predictable.
was:
The ORC scanners uses an external library to read ORC files. The library reads
the file contents into its own memory representation. It is a vectorized
representation similar to the Arrow format.
Impala needs to convert the ORC row batch to an Impala row batch. Currently the
conversion happens row-wise and value-by-value via virtual function calls:
[https://github.com/apache/impala/blob/85425b81f04c856d7d5ec375242303f78ec7964e/be/src/exec/hdfs-orc-scanner.cc#L671]
[https://github.com/apache/impala/blob/85425b81f04c856d7d5ec375242303f78ec7964e/be/src/exec/orc-column-readers.cc#L352]
Instead of this approach it could work similarly to the Parquet scanner that
fills the columns one-by-one into a scratch batch, then evaluate the conjuncts
on the scratch batch. For more details see HdfsParquetScanner::AssembleRows():
[https://github.com/apache/impala/blob/85425b81f04c856d7d5ec375242303f78ec7964e/be/src/exec/parquet/hdfs-parquet-scanner.cc#L1077-L1088]
This way we'll need a lot less virtual function calls, also the memory
reads/writes will be much more localized and predictable.
> ORC scanner could be vectorized
> -------------------------------
>
> Key: IMPALA-9228
> URL: https://issues.apache.org/jira/browse/IMPALA-9228
> Project: IMPALA
> Issue Type: Improvement
> Reporter: Zoltán Borók-Nagy
> Priority: Major
> Labels: orc
>
> The ORC scanners uses an external library to read ORC files. The library
> reads the file contents into its own memory representation. It is a
> vectorized representation similar to the Arrow format.
> Impala needs to convert the ORC row batch to an Impala row batch. Currently
> the conversion happens row-wise via virtual function calls:
> [https://github.com/apache/impala/blob/85425b81f04c856d7d5ec375242303f78ec7964e/be/src/exec/hdfs-orc-scanner.cc#L671]
> [https://github.com/apache/impala/blob/85425b81f04c856d7d5ec375242303f78ec7964e/be/src/exec/orc-column-readers.cc#L352]
> Instead of this approach it could work similarly to the Parquet scanner that
> fills the columns one-by-one into a scratch batch, then evaluate the
> conjuncts on the scratch batch. For more details see
> HdfsParquetScanner::AssembleRows():
> [https://github.com/apache/impala/blob/85425b81f04c856d7d5ec375242303f78ec7964e/be/src/exec/parquet/hdfs-parquet-scanner.cc#L1077-L1088]
> This way we'll need a lot less virtual function calls, also the memory
> reads/writes will be much more localized and predictable.
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