Chao Sun created SPARK-35003:
--------------------------------
Summary: Improve performance for reading smallint in vectorized
Parquet reader
Key: SPARK-35003
URL: https://issues.apache.org/jira/browse/SPARK-35003
Project: Spark
Issue Type: Improvement
Components: SQL
Affects Versions: 3.2.0
Reporter: Chao Sun
Currently {{VectorizedRleValuesReader}} reads short in the following way:
{code:java}
for (int i = 0; i < n; i++) {
c.putShort(rowId + i, (short)data.readInteger());
}
{code}
For PLAIN encoding {{readInteger}} is done via:
{code:java}
public final int readInteger() {
return getBuffer(4).getInt();
}
{code}
which means it needs to repeatedly call {{slice}} buffer which is more
expensive than calling it once in a big chunk and then reading the ints out.
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