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Posted to issues@carbondata.apache.org by ravipesala <gi...@git.apache.org> on 2017/08/14 08:36:12 UTC
[GitHub] carbondata pull request #1240: [CARBONDATA-1365] add RLE codec implementatio...
Github user ravipesala commented on a diff in the pull request:
https://github.com/apache/carbondata/pull/1240#discussion_r132898313
--- Diff: core/src/main/java/org/apache/carbondata/core/datastore/page/encoding/RLECodec.java ---
@@ -0,0 +1,417 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.carbondata.core.datastore.page.encoding;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.carbondata.core.datastore.page.ColumnPage;
+import org.apache.carbondata.core.datastore.page.ComplexColumnPage;
+import org.apache.carbondata.core.datastore.page.statistics.SimpleStatsResult;
+import org.apache.carbondata.core.memory.MemoryException;
+import org.apache.carbondata.core.metadata.CodecMetaFactory;
+import org.apache.carbondata.core.metadata.datatype.DataType;
+
+/**
+ * RLE encoding implementation for integral column page.
+ * This encoding keeps track of repeated-run and non-repeated-run, and make use
+ * of the highest bit of the length field to indicate the type of run.
+ * The length field is encoded as 32bits value.
+ *
+ * For example: input data {5, 5, 1, 2, 3, 3, 3, 3, 3} will be encoded to
+ * {0x00, 0x00, 0x00, 0x02, 0x05, (repeated-run, 2 values of 5)
+ * 0x80, 0x00, 0x00, 0x03, 0x01, 0x02, 0x03, (non-repeated-run, 3 values: 1, 2, 3)
+ * 0x00, 0x00, 0x00, 0x04, 0x03} (repeated-run, 4 values of 3)
+ */
+public class RLECodec implements ColumnPageCodec {
+
+ enum RUN_STATE { INIT, START, REPEATED_RUN, NONREPEATED_RUN }
+
+ private DataType dataType;
+ private int pageSize;
+
+ /**
+ * New RLECodec
+ * @param dataType data type of the raw column page before encode
+ * @param pageSize page size of the raw column page before encode
+ */
+ RLECodec(DataType dataType, int pageSize) {
+ this.dataType = dataType;
+ this.pageSize = pageSize;
+ }
+
+ @Override
+ public String getName() {
+ return "RLECodec";
+ }
+
+ @Override
+ public EncodedColumnPage encode(ColumnPage input) throws MemoryException, IOException {
+ Encoder encoder = new Encoder();
+ return encoder.encode(input);
+ }
+
+ @Override
+ public EncodedColumnPage[] encodeComplexColumn(ComplexColumnPage input) {
+ throw new UnsupportedOperationException("complex column does not support RLE encoding");
+ }
+
+ @Override
+ public ColumnPage decode(byte[] input, int offset, int length) throws MemoryException,
+ IOException {
+ Decoder decoder = new Decoder(dataType, pageSize);
+ return decoder.decode(input, offset, length);
+ }
+
+ // This codec supports integral type only
+ private void validateDataType(DataType dataType) {
+ switch (dataType) {
+ case BYTE:
+ case SHORT:
+ case INT:
+ case LONG:
+ break;
+ default:
+ throw new UnsupportedOperationException(dataType + " is not supported for RLE");
+ }
+ }
+
+ private class Encoder {
+ // While encoding RLE, this class internally work as a state machine
+ // INIT state is the initial state before any value comes
+ // START state is the start for each run
+ // REPEATED_RUN state means it is collecting repeated values (`lastValue`)
+ // NONREPEATED_RUN state means it is collecting non-repeated values (`nonRepeatValues`)
+ private RUN_STATE runState;
+
+ // count for each run, either REPEATED_RUN or NONREPEATED_RUN
+ private int valueCount;
+
+ // collected value for REPEATED_RUN
+ private Object lastValue;
+
+ // collected value for NONREPEATED_RUN
+ private List<Object> nonRepeatValues;
+
+ // data type of input page
+ private DataType dataType;
+
+ // output stream for encoded data
+ private ByteArrayOutputStream bao;
+ private DataOutputStream stream;
+
+ private Encoder() {
+ this.runState = RUN_STATE.INIT;
+ this.valueCount = 0;
+ this.nonRepeatValues = new ArrayList<>();
+ this.bao = new ByteArrayOutputStream();
+ this.stream = new DataOutputStream(bao);
+ }
+
+ private EncodedColumnPage encode(ColumnPage input) throws MemoryException, IOException {
+ validateDataType(input.getDataType());
+ this.dataType = input.getDataType();
+ switch (dataType) {
+ case BYTE:
+ byte[] bytePage = input.getBytePage();
+ for (int i = 0; i < bytePage.length; i++) {
+ putValue(bytePage[i]);
+ }
+ break;
+ case SHORT:
+ short[] shortPage = input.getShortPage();
+ for (int i = 0; i < shortPage.length; i++) {
+ putValue(shortPage[i]);
+ }
+ break;
+ case INT:
+ int[] intPage = input.getIntPage();
+ for (int i = 0; i < intPage.length; i++) {
+ putValue(intPage[i]);
+ }
+ break;
+ case LONG:
+ long[] longPage = input.getLongPage();
+ for (int i = 0; i < longPage.length; i++) {
+ putValue(longPage[i]);
+ }
+ break;
+ default:
+ throw new UnsupportedOperationException(input.getDataType() +
+ " does not support RLE encoding");
+ }
+ byte[] encoded = collectResult();
+ SimpleStatsResult stats = (SimpleStatsResult) input.getStatistics();
+ return new EncodedMeasurePage(
+ input.getPageSize(),
+ encoded,
+ CodecMetaFactory.createMeta(stats, input.getDataType()),
+ stats.getNullBits());
+ }
+
+ private void putValue(Object value) throws IOException {
+ if (runState == RUN_STATE.INIT) {
+ startNewRun(value);
+ } else {
+ if (lastValue.equals(value)) {
+ putRepeatValue(value);
+ } else {
+ putNonRepeatValue(value);
+ }
+ }
+ }
+
+ // when last row is reached, write out all collected data
+ private byte[] collectResult() throws IOException {
+ switch (runState) {
+ case REPEATED_RUN:
+ writeRunLength(valueCount);
+ writeRunValue(lastValue);
+ break;
+ case NONREPEATED_RUN:
+ writeRunLength(valueCount | 0x80000000);
--- End diff --
I think writing short is enough as of now. Because we are restricting page size in short only
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