When the column carries the logical type {@code DECIMAL}, the bytes read + * here are the big-endian two's-complement form of the un-scaled integer. + * It slices the requested number of bytes without flipping and + * returns them as a {@link org.apache.parquet.io.api.Binary}. + */ public class BinaryPlainValuesReader extends ValuesReader { private static final Logger LOG = LoggerFactory.getLogger(BinaryPlainValuesReader.class); private ByteBufferInputStream in; diff --git a/parquet-column/src/main/java/org/apache/parquet/column/values/plain/PlainValuesWriter.java b/parquet-column/src/main/java/org/apache/parquet/column/values/plain/PlainValuesWriter.java index c7069bc092..ec725597cf 100644 --- a/parquet-column/src/main/java/org/apache/parquet/column/values/plain/PlainValuesWriter.java +++ b/parquet-column/src/main/java/org/apache/parquet/column/values/plain/PlainValuesWriter.java @@ -32,7 +32,15 @@ import org.slf4j.LoggerFactory; /** - * Plain encoding except for booleans + * Plain encoding except for booleans. + * + *
Endianness note for DECIMAL: when a DECIMAL value is stored in a + * BYTE_ARRAY column, the {@link org.apache.parquet.io.api.Binary} + * passed to this writer already contains the big-endian two's-complement bytes + * of the un-scaled integer (the same bytes produced by + * {@link java.math.BigInteger#toByteArray()}). This writer keeps those bytes + * exactly as they are and only adds the 4-byte little-endian length prefix + * required by the PLAIN encoding. Bytes are not re-ordered.
*/ public class PlainValuesWriter extends ValuesWriter { private static final Logger LOG = LoggerFactory.getLogger(PlainValuesWriter.class);