uk.ac.starlink.parquet.Encoder Maven / Gradle / Ivy
package uk.ac.starlink.parquet;
import org.apache.parquet.io.api.RecordConsumer;
import org.apache.parquet.schema.Type;
/**
* Defines transmission of a java value type to a RecordConsumer
* for writing to parquet tables.
*
* @author Mark Taylor
* @since 25 Feb 2021
*/
public interface Encoder {
/**
* Returns the name of the column that will be written to the parquet file.
* This is the top-level field, which may correspond to a group type
* containing lower-level elements, which will be assigned subordinate
* names automatically.
*
* Note this name must obey the (undocumented?) parquet field
* syntax constraints; it seems that roughly it has to look like
* a java token.
*
* @return field name
*/
String getColumnName();
/**
* Returns the type of the top-level field that will be written.
* This may be a primitive type or a group type.
*
* @return column type
*/
Type getColumnType();
/**
* Passes a supplied value representing a cell of this encoder's column
* to a record consumer. This is called between
* RecordConsumer startField and endField
* calls, but if additional structuring calls are required they
* must be done by this method.
*
* @param value typed value to write
* @param consumer value consumer
*/
void addValue( Object value, RecordConsumer consumer );
}