content: /*
   * 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;
  
  import java.nio.ByteBuffer;
  import java.util.concurrent.Callable;
  
  import org.apache.carbondata.core.constants.CarbonCommonConstants;
  import org.apache.carbondata.core.datastore.TableSpec;
  import org.apache.carbondata.core.datastore.columnar.UnBlockIndexer;
  import org.apache.carbondata.core.datastore.compression.CompressorFactory;
  import org.apache.carbondata.core.datastore.page.encoding.EncodedColumnPage;
  import org.apache.carbondata.core.keygenerator.KeyGenerator;
  import org.apache.carbondata.core.keygenerator.factory.KeyGeneratorFactory;
  import org.apache.carbondata.core.localdictionary.generator.LocalDictionaryGenerator;
  import org.apache.carbondata.core.util.CarbonUtil;
  import org.apache.carbondata.format.Encoding;
  
  public class DecoderBasedFallbackEncoder implements Callable<FallbackEncodedColumnPage> {
    /**
     * actual local dictionary generated column page
     */
    private EncodedColumnPage encodedColumnPage;
  
    /**
     * actual index in the page
     * this is required as in a blocklet few pages will be local dictionary
     * encoded and few pages will be plain text encoding
     * in this case local dictionary encoded page
     */
    private int pageIndex;
  
    private LocalDictionaryGenerator localDictionaryGenerator;
  
    public DecoderBasedFallbackEncoder(EncodedColumnPage encodedColumnPage, int pageIndex,
        LocalDictionaryGenerator localDictionaryGenerator) {
      this.encodedColumnPage = encodedColumnPage;
      this.pageIndex = pageIndex;
      this.localDictionaryGenerator = localDictionaryGenerator;
    }
  
    @Override
    public FallbackEncodedColumnPage call() throws Exception {
      int pageSize =
          encodedColumnPage.getActualPage().getPageSize();
      int offset = 0;
      int[] reverseInvertedIndex = new int[pageSize];
      for (int i = 0; i < pageSize; i++) {
        reverseInvertedIndex[i] = i;
      }
      int[] rlePage;
  
      // uncompress the encoded column page
      byte[] bytes = CompressorFactory.getInstance().getCompressor(
          encodedColumnPage.getActualPage().getColumnPageEncoderMeta().getCompressorName())
          .unCompressByte(encodedColumnPage.getEncodedData().array(), offset,
              encodedColumnPage.getPageMetadata().data_page_length);
  
      offset += encodedColumnPage.getPageMetadata().data_page_length;
      ByteBuffer data = ByteBuffer.wrap(encodedColumnPage.getEncodedData().array());
  
      // if encoded with inverted index, get all the inverted indexes
      if (CarbonUtil
          .hasEncoding(encodedColumnPage.getPageMetadata().encoders, Encoding.INVERTED_INDEX)) {
        int[] invertedIndexes = CarbonUtil
            .getUnCompressColumnIndex(encodedColumnPage.getPageMetadata().rowid_page_length, data,
                offset);
        offset += encodedColumnPage.getPageMetadata().rowid_page_length;
        // get all the reverse inverted index
        reverseInvertedIndex = CarbonUtil.getInvertedReverseIndex(invertedIndexes);
      }
      // if rle is applied then uncompress then actual data based on rle
      if (CarbonUtil.hasEncoding(encodedColumnPage.getPageMetadata().encoders, Encoding.RLE)) {
        rlePage =
            CarbonUtil.getIntArray(data, offset, encodedColumnPage.getPageMetadata().rle_page_length);
        // uncompress the data with rle indexes
        bytes = UnBlockIndexer
            .uncompressData(bytes, rlePage, CarbonCommonConstants.LOCAL_DICT_ENCODED_BYTEARRAY_SIZE,
                bytes.length);
      }
  
      // disable encoding using local dictionary
      encodedColumnPage.getActualPage().disableLocalDictEncoding();
  
      // create a new column page which will have actual data instead of encoded data
      ColumnPage actualDataColumnPage =
          ColumnPage.newPage(encodedColumnPage.getActualPage().getColumnPageEncoderMeta(),
              encodedColumnPage.getActualPage().getPageSize());
  
      // uncompressed data from encoded column page is dictionary data, get the dictionary data using
      // KeyGenerator
      KeyGenerator keyGenerator = KeyGeneratorFactory
          .getKeyGenerator(new int[] { CarbonCommonConstants.LOCAL_DICTIONARY_MAX + 1 });
  
      actualDataColumnPage.setStatsCollector(encodedColumnPage.getActualPage().statsCollector);
  
      // get the actual data for each dictionary data and put the actual data in new page
      int rowId = 0;
      for (int i = 0; i < pageSize; i++) {
        int index = reverseInvertedIndex[i] * 3;
        int keyArray = (int) keyGenerator.getKeyArray(bytes, index)[0];
        if (actualDataColumnPage instanceof LVByteBufferColumnPage) {
          //TODO It's a quick fix, we can fallback to old logic adding Length outside of
          // LVByteBufferColumnPage. Update the page data with Length before adding to column page.
          // so it won't be added again when fallback scenario occurs.
          // Though this is not a bottleneck as after fallback only encoded page will be decoded
          // and System.array copy is very fast. So for few pages it won't impact much
          byte[] dictionaryKeyBasedOnValue =
              localDictionaryGenerator.getDictionaryKeyBasedOnValue(keyArray);
          byte[] output =
              new byte[dictionaryKeyBasedOnValue.length - localDictionaryGenerator.getLVLength()];
          System
              .arraycopy(dictionaryKeyBasedOnValue, localDictionaryGenerator.getLVLength(), output, 0,
                  output.length);
          actualDataColumnPage.putBytes(rowId++, output);
        } else {
          actualDataColumnPage
              .putBytes(rowId++, localDictionaryGenerator.getDictionaryKeyBasedOnValue(keyArray));
        }
      }
  
      // get column spec for existing column page
      TableSpec.ColumnSpec columnSpec = encodedColumnPage.getActualPage().getColumnSpec();
      FallbackEncodedColumnPage fallBackEncodedColumnPage =
          CarbonUtil.getFallBackEncodedColumnPage(actualDataColumnPage, pageIndex, columnSpec);
      // here freeing the memory of new column page created as fallback is done and
      // fallBackEncodedColumnPage is created using new page of actual data
      // This is required to free the memory once it is of no use
      actualDataColumnPage.freeMemory();
      encodedColumnPage.cleanBuffer();
      return fallBackEncodedColumnPage;
    }
  
  }
  