Fokko commented on code in PR #3494:
URL: https://github.com/apache/parquet-java/pull/3494#discussion_r3156914189
##########
parquet-column/src/main/java/org/apache/parquet/column/values/plain/PlainValuesReader.java:
##########
@@ -19,120 +19,92 @@
package org.apache.parquet.column.values.plain;
import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
import org.apache.parquet.bytes.ByteBufferInputStream;
import org.apache.parquet.bytes.LittleEndianDataInputStream;
import org.apache.parquet.column.values.ValuesReader;
-import org.apache.parquet.io.ParquetDecodingException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
- * Plain encoding for float, double, int, long
+ * Plain encoding for float, double, int, long.
+ *
+ * <p>Reads directly from a {@link ByteBuffer} with {@link
ByteOrder#LITTLE_ENDIAN} byte order,
+ * bypassing the {@link LittleEndianDataInputStream} wrapper to avoid
per-value virtual dispatch
+ * overhead. The underlying page data is obtained as a single contiguous
{@link ByteBuffer} via
+ * {@link ByteBufferInputStream#slice(int)}.
*/
public abstract class PlainValuesReader extends ValuesReader {
private static final Logger LOG =
LoggerFactory.getLogger(PlainValuesReader.class);
- protected LittleEndianDataInputStream in;
+ ByteBuffer buffer;
@Override
public void initFromPage(int valueCount, ByteBufferInputStream stream)
throws IOException {
LOG.debug("init from page at offset {} for length {}", stream.position(),
stream.available());
- this.in = new LittleEndianDataInputStream(stream.remainingStream());
+ int available = stream.available();
+ if (available > 0) {
+ this.buffer = stream.slice(available).order(ByteOrder.LITTLE_ENDIAN);
+ } else {
+ this.buffer = ByteBuffer.allocate(0).order(ByteOrder.LITTLE_ENDIAN);
Review Comment:
Should we introduce a constant:
```
private static final ByteBuffer EMPTY =
ByteBuffer.allocate(0).order(ByteOrder.LITTLE_ENDIAN);
```
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