parquet.column.ColumnReader Maven / Gradle / Ivy
/**
* Copyright 2012 Twitter, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package parquet.column;
import parquet.io.api.Binary;
/**
* Reader for (repetition level, definition level, values) triplets.
* At any given point in time, a ColumnReader points to a single (r, d, v) triplet.
* In order to move to the next triplet, call {@link #consume()}.
*
* Depending on the type and the encoding of the column only a subset of the get* methods are implemented.
* Dictionary specific methods enable the upper layers to read the dictionary IDs without decoding the data.
* In particular the Converter will decode the strings in the dictionary only once and iterate on the
* dictionary IDs instead of the values.
*
* Each iteration looks at the current definition level and value as well as the next
* repetition level:
* - The current definition level defines if the value is null.
* - If the value is defined we can read it with the correct get*() method.
* - Looking ahead to the next repetition determines what is the next column to read for in the FSA.
*
* @author Julien Le Dem
*/
public interface ColumnReader {
/**
* @return the totalCount of values to be consumed
*/
long getTotalValueCount();
/**
* Consume the current triplet, moving to the next value.
*/
void consume();
/**
* must return 0 when isFullyConsumed() == true
* @return the repetition level for the current value
*/
int getCurrentRepetitionLevel();
/**
* @return the definition level for the current value
*/
int getCurrentDefinitionLevel();
/**
* writes the current value to the converter
*/
void writeCurrentValueToConverter();
/**
* Skip the current value
*/
void skip();
/**
* available when the underlying encoding is dictionary based
* @return the dictionary id for the current value
*/
int getCurrentValueDictionaryID();
/**
* @return the current value
*/
int getInteger();
/**
* @return the current value
*/
boolean getBoolean();
/**
* @return the current value
*/
long getLong();
/**
* @return the current value
*/
Binary getBinary();
/**
* @return the current value
*/
float getFloat();
/**
* @return the current value
*/
double getDouble();
/**
* @return Descriptor of the column.
*/
ColumnDescriptor getDescriptor();
}