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https://issues.apache.org/jira/browse/IMPALA-8381?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16809886#comment-16809886
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Daniel Becker edited comment on IMPALA-8381 at 4/4/19 2:01 PM:
---------------------------------------------------------------
Some measurements:
Running the following query in the database tpch_parquet:
{code:java}
set num_nodes=1; select max(l_orderkey) from lineitem;{code}
we found the following results averaging the MaterializeTupleTime values over
100 runs with and without the "if":
Without "if": 14.3464ms
With "if": 16.42624ms
This is a 14% improvement in MaterializeTupleTime in this query.
The total query time was 0.11s, the ~2ms gain is a little less than 2%.
was (Author: daniel.becker):
Some measurements:
Running the following query in the database tpch_parquet:
{code:java}
set num_nodes=1; select max(l_orderkey) from lineitem;{code}
we found the following results averaging the MaterializeTupleTime(*) values
over 100 runs with and without the "if":
Without "if": 14.3464ms
With "if": 16.42624ms
This is a 14% improvement in MaterializeTupleTime in this query.
The total query time was 0.11s, the ~2ms gain is a little less than 2%.
> Remove branch from ParquetPlainEncoder::Decode()
> ------------------------------------------------
>
> Key: IMPALA-8381
> URL: https://issues.apache.org/jira/browse/IMPALA-8381
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend
> Reporter: Csaba Ringhofer
> Priority: Minor
> Labels: newbie, parquet, performance, ramp-up
>
> Removing the "if" at
> https://github.com/apache/impala/blob/5670f96b828d57f9e36510bb9af02bcc31de775c/be/src/exec/parquet/parquet-common.h#L203
> can lead to 1.5x speed up in plain decoding (type=int32, stride=16). For
> primitive types, the same check can be done for a whole batch, so the speedup
> can be gained for large batches without loosing safety. The only Parquet type
> where this check is needed per element is BYTE_ARRAY (typically used for
> STRING columns), which already has a template specialization for
> ParquetPlainEncoder::Decode().
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