[GitHub] [druid] abhishekagarwal87 commented on a change in pull request #10224: Segment backed broadcast join IndexedTable

[GitBox <gi...@apache.org>]

abhishekagarwal87 commented on a change in pull request #10224:
URL: https://github.com/apache/druid/pull/10224#discussion_r471313578



##########
File path: processing/src/main/java/org/apache/druid/segment/join/table/BroadcastSegmentIndexedTable.java
##########
@@ -0,0 +1,255 @@
+/*
+ * 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.druid.segment.join.table;
+
+import com.google.common.base.Preconditions;
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import it.unimi.dsi.fastutil.ints.IntList;
+import org.apache.druid.java.util.common.IAE;
+import org.apache.druid.java.util.common.granularity.Granularities;
+import org.apache.druid.java.util.common.guava.Sequence;
+import org.apache.druid.java.util.common.guava.Sequences;
+import org.apache.druid.java.util.common.io.Closer;
+import org.apache.druid.java.util.common.logger.Logger;
+import org.apache.druid.segment.BaseObjectColumnValueSelector;
+import org.apache.druid.segment.ColumnSelectorFactory;
+import org.apache.druid.segment.Cursor;
+import org.apache.druid.segment.NilColumnValueSelector;
+import org.apache.druid.segment.QueryableIndex;
+import org.apache.druid.segment.QueryableIndexColumnSelectorFactory;
+import org.apache.druid.segment.QueryableIndexSegment;
+import org.apache.druid.segment.QueryableIndexStorageAdapter;
+import org.apache.druid.segment.SimpleAscendingOffset;
+import org.apache.druid.segment.VirtualColumns;
+import org.apache.druid.segment.column.BaseColumn;
+import org.apache.druid.segment.column.ColumnHolder;
+import org.apache.druid.segment.column.RowSignature;
+import org.apache.druid.segment.column.ValueType;
+import org.apache.druid.segment.data.ReadableOffset;
+import org.apache.druid.segment.filter.Filters;
+import org.joda.time.chrono.ISOChronology;
+
+import javax.annotation.Nullable;
+import java.io.Closeable;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+public class BroadcastSegmentIndexedTable implements IndexedTable
+{
+  private static final Logger LOG = new Logger(BroadcastSegmentIndexedTable.class);
+
+  private final QueryableIndexSegment segment;
+  private final QueryableIndexStorageAdapter adapter;
+  private final QueryableIndex queryableIndex;
+  private final Set<String> keyColumns;
+  private final RowSignature rowSignature;
+  private final String version;
+  private final List<Map<Object, IntList>> keyColumnsIndex;
+
+  public BroadcastSegmentIndexedTable(final QueryableIndexSegment theSegment, final Set<String> keyColumns, final String version)
+  {
+    this.keyColumns = keyColumns;
+    this.version = version;
+    this.segment = Preconditions.checkNotNull(theSegment, "Segment must not be null");
+    this.adapter = Preconditions.checkNotNull(
+        (QueryableIndexStorageAdapter) segment.asStorageAdapter(),
+        "Segment[%s] must have a QueryableIndexStorageAdapter",
+        segment.getId()
+    );
+    this.queryableIndex = Preconditions.checkNotNull(
+        segment.asQueryableIndex(),
+        "Segment[%s] must have a QueryableIndexSegment",
+        segment.getId()
+    );
+
+    RowSignature.Builder sigBuilder = RowSignature.builder();
+    sigBuilder.add(ColumnHolder.TIME_COLUMN_NAME, ValueType.LONG);
+    for (String column : queryableIndex.getColumnNames()) {
+      sigBuilder.add(column, adapter.getColumnCapabilities(column).getType());
+    }
+    this.rowSignature = sigBuilder.build();
+
+    // initialize keycolumn index maps
+    this.keyColumnsIndex = new ArrayList<>(rowSignature.size());
+    final List<String> keyColumnNames = new ArrayList<>(keyColumns.size());
+    for (int i = 0; i < rowSignature.size(); i++) {
+      final Map<Object, IntList> m;
+      final String columnName = rowSignature.getColumnName(i);
+      if (keyColumns.contains(columnName)) {
+        m = new HashMap<>();
+        keyColumnNames.add(columnName);
+      } else {
+        m = null;
+      }
+      keyColumnsIndex.add(m);
+    }
+
+    // sort of like the dump segment tool, but build key column indexes when reading the segment
+    final Sequence<Cursor> cursors = adapter.makeCursors(
+        Filters.toFilter(null),
+        queryableIndex.getDataInterval().withChronology(ISOChronology.getInstanceUTC()),
+        VirtualColumns.EMPTY,
+        Granularities.ALL,
+        false,
+        null
+    );
+
+    final Sequence<Integer> sequence = Sequences.map(
+        cursors,
+        cursor -> {
+          if (cursor == null) {
+            return 0;
+          }
+          int rowNumber = 0;
+          ColumnSelectorFactory columnSelectorFactory = cursor.getColumnSelectorFactory();
+
+          // this should really be optimized to use dimension selectors where possible to populate indexes from bitmap
+          // indexes, but, an optimization for another day
+          final List<BaseObjectColumnValueSelector> selectors = keyColumnNames
+              .stream()
+              .map(columnName -> {
+                // multi-value dimensions are not currently supported
+                if (adapter.getColumnCapabilities(columnName).hasMultipleValues().isMaybeTrue()) {
+                  return NilColumnValueSelector.instance();
+                }
+                return columnSelectorFactory.makeColumnValueSelector(columnName);
+              })
+              .collect(Collectors.toList());
+
+          while (!cursor.isDone()) {
+            for (int keyColumnSelectorIndex = 0; keyColumnSelectorIndex < selectors.size(); keyColumnSelectorIndex++) {
+              final String keyColumnName = keyColumnNames.get(keyColumnSelectorIndex);
+              final int columnPosition = rowSignature.indexOf(keyColumnName);
+              final Map<Object, IntList> keyColumnValueIndex = keyColumnsIndex.get(columnPosition);
+              final Object key = selectors.get(keyColumnSelectorIndex).getObject();
+              if (key != null) {
+                final IntList array = keyColumnValueIndex.computeIfAbsent(key, k -> new IntArrayList());
+                array.add(rowNumber);
+              }
+            }
+
+            if (rowNumber % 100_000 == 0) {
+              if (rowNumber == 0) {
+                LOG.debug("Indexed first row for table %s", theSegment.getId());
+              } else {
+                LOG.debug("Indexed row %s for table %s", rowNumber, theSegment.getId());
+              }
+            }
+            rowNumber++;
+            cursor.advance();
+          }
+          return rowNumber;
+        }
+    );
+
+    Integer totalRows = sequence.accumulate(0, (accumulated, in) -> accumulated += in);
+    LOG.info("Created BroadcastSegmentIndexedTable with %s rows.", totalRows);
+  }
+
+  @Override
+  public String version()
+  {
+    return version;
+  }
+
+  @Override
+  public Set<String> keyColumns()
+  {
+    return keyColumns;
+  }
+
+  @Override
+  public RowSignature rowSignature()
+  {
+    return rowSignature;
+  }
+
+  @Override
+  public int numRows()
+  {
+    return adapter.getNumRows();
+  }
+
+  @Override
+  public Index columnIndex(int column)
+  {
+    return RowBasedIndexedTable.getKeyColumnIndex(column, keyColumnsIndex, rowSignature);
+  }
+
+  @Override
+  public Reader columnReader(int column)
+  {
+    if (column < 0 || rowSignature.getColumnName(0) == null) {

Review comment:
       ```suggestion
       if (column < 0 || rowSignature.getColumnName(column) == null) {
   ```




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