[GitHub] [pinot] weixiangsun commented on a change in pull request #7781: Add Post-Aggregation Gapfilling functionality.

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

weixiangsun commented on a change in pull request #7781:
URL: https://github.com/apache/pinot/pull/7781#discussion_r751450736



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File path: pinot-core/src/main/java/org/apache/pinot/core/query/reduce/GapFillGroupByDataTableReducer.java
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@@ -0,0 +1,725 @@
+/**
+ * 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.pinot.core.query.reduce;
+
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import org.apache.pinot.common.exception.QueryException;
+import org.apache.pinot.common.metrics.BrokerGauge;
+import org.apache.pinot.common.metrics.BrokerMeter;
+import org.apache.pinot.common.metrics.BrokerMetrics;
+import org.apache.pinot.common.request.context.ExpressionContext;
+import org.apache.pinot.common.request.context.FilterContext;
+import org.apache.pinot.common.response.broker.AggregationResult;
+import org.apache.pinot.common.response.broker.BrokerResponseNative;
+import org.apache.pinot.common.response.broker.GroupByResult;
+import org.apache.pinot.common.response.broker.QueryProcessingException;
+import org.apache.pinot.common.response.broker.ResultTable;
+import org.apache.pinot.common.utils.DataSchema;
+import org.apache.pinot.common.utils.DataSchema.ColumnDataType;
+import org.apache.pinot.common.utils.DataTable;
+import org.apache.pinot.core.data.table.ConcurrentIndexedTable;
+import org.apache.pinot.core.data.table.IndexedTable;
+import org.apache.pinot.core.data.table.Key;
+import org.apache.pinot.core.data.table.Record;
+import org.apache.pinot.core.data.table.SimpleIndexedTable;
+import org.apache.pinot.core.data.table.UnboundedConcurrentIndexedTable;
+import org.apache.pinot.core.operator.combine.GroupByOrderByCombineOperator;
+import org.apache.pinot.core.query.aggregation.function.AggregationFunction;
+import org.apache.pinot.core.query.aggregation.function.AggregationFunctionUtils;
+import org.apache.pinot.core.query.aggregation.groupby.AggregationGroupByTrimmingService;
+import org.apache.pinot.core.query.request.context.QueryContext;
+import org.apache.pinot.core.query.selection.SelectionOperatorUtils;
+import org.apache.pinot.core.transport.ServerRoutingInstance;
+import org.apache.pinot.core.util.GroupByUtils;
+import org.apache.pinot.core.util.QueryOptionsUtils;
+import org.apache.pinot.core.util.trace.TraceRunnable;
+import org.apache.pinot.spi.data.DateTimeFormatSpec;
+import org.apache.pinot.spi.data.DateTimeGranularitySpec;
+
+
+/**
+ * Helper class to reduce data tables and set group by results into the BrokerResponseNative
+ */
+@SuppressWarnings({"rawtypes", "unchecked"})
+public class GapFillGroupByDataTableReducer implements DataTableReducer {
+  private static final int MIN_DATA_TABLES_FOR_CONCURRENT_REDUCE = 2; // TBD, find a better value.
+
+  private final QueryContext _queryContext;
+  private final AggregationFunction[] _aggregationFunctions;
+  private final int _numAggregationFunctions;
+  private final List<ExpressionContext> _groupByExpressions;
+  private final int _numGroupByExpressions;
+  private final int _numColumns;
+  private final boolean _preserveType;
+  private final boolean _groupByModeSql;
+  private final boolean _responseFormatSql;
+  private final boolean _sqlQuery;
+  private final DateTimeGranularitySpec _dateTimeGranularity;
+  private final DateTimeFormatSpec _dateTimeFormatter;
+  private final long _startMs;
+  private final long _endMs;
+  private final Set<Key> _primaryKeys;
+  private final Map<Key, Object[]> _previous;
+  private final int _numOfKeyColumns;
+
+  GapFillGroupByDataTableReducer(QueryContext queryContext) {
+    _queryContext = queryContext;
+    _aggregationFunctions = queryContext.getAggregationFunctions();
+    assert _aggregationFunctions != null;
+    _numAggregationFunctions = _aggregationFunctions.length;
+    _groupByExpressions = queryContext.getGroupByExpressions();
+    assert _groupByExpressions != null;
+    _numGroupByExpressions = _groupByExpressions.size();
+    _numColumns = _numAggregationFunctions + _numGroupByExpressions;
+    Map<String, String> queryOptions = queryContext.getQueryOptions();
+    _preserveType = QueryOptionsUtils.isPreserveType(queryOptions);
+    _groupByModeSql = QueryOptionsUtils.isGroupByModeSQL(queryOptions);
+    _responseFormatSql = QueryOptionsUtils.isResponseFormatSQL(queryOptions);
+    _sqlQuery = queryContext.getBrokerRequest().getPinotQuery() != null;
+
+    ExpressionContext firstExpressionContext = _queryContext.getSelectExpressions().get(0);
+    List<ExpressionContext> args = firstExpressionContext.getFunction().getArguments();
+    _dateTimeFormatter = new DateTimeFormatSpec(args.get(1).getLiteral());
+    _dateTimeGranularity = new DateTimeGranularitySpec(args.get(4).getLiteral());
+    String start = args.get(2).getLiteral();
+    String end = args.get(3).getLiteral();
+    _startMs = truncate(_dateTimeFormatter.fromFormatToMillis(start));
+    _endMs = truncate(_dateTimeFormatter.fromFormatToMillis(end));
+    _primaryKeys = new HashSet<>();
+    _previous = new HashMap<>();
+    _numOfKeyColumns = _queryContext.getGroupByExpressions().size() - 1;
+  }
+
+  private long truncate(long epoch) {
+    int sz = _dateTimeGranularity.getSize();
+    return epoch / sz * sz;
+  }
+
+  /**
+   * Reduces and sets group by results into ResultTable, if responseFormat = sql
+   * By default, sets group by results into GroupByResults
+   */
+  @Override
+  public void reduceAndSetResults(String tableName, DataSchema dataSchema,
+      Map<ServerRoutingInstance, DataTable> dataTableMap, BrokerResponseNative brokerResponseNative,
+      DataTableReducerContext reducerContext, BrokerMetrics brokerMetrics) {
+    assert dataSchema != null;
+    int resultSize = 0;
+    Collection<DataTable> dataTables = dataTableMap.values();
+
+    // For group by, PQL behavior is different than the SQL behavior. In the PQL way,
+    // a result is generated for each aggregation in the query,
+    // and the group by keys are not the same across the aggregations
+    // This PQL style of execution makes it impossible to support order by on group by.
+    //
+    // We could not simply change the group by execution behavior,
+    // as that would not be backward compatible for existing users of group by.
+    // As a result, we have 2 modes of group by execution - pql and sql - which can be controlled via query options
+    //
+    // Long term, we may completely move to sql, and keep only full sql mode alive
+    // Until then, we need to support responseFormat = sql for both the modes of execution.
+    // The 4 variants are as described below:
+
+    if (_groupByModeSql) {
+
+      if (_responseFormatSql) {
+        // 1. groupByMode = sql, responseFormat = sql
+        // This is the primary SQL compliant group by
+
+        try {
+          setSQLGroupByInResultTable(brokerResponseNative, dataSchema, dataTables, reducerContext, tableName,
+              brokerMetrics);
+        } catch (TimeoutException e) {
+          brokerResponseNative.getProcessingExceptions()
+              .add(new QueryProcessingException(QueryException.BROKER_TIMEOUT_ERROR_CODE, e.getMessage()));
+        }
+        resultSize = brokerResponseNative.getResultTable().getRows().size();
+      } else {
+        // 2. groupByMode = sql, responseFormat = pql
+        // This mode will invoke SQL style group by execution, but present results in PQL way
+        // This mode is useful for users who want to avail of SQL compliant group by behavior,
+        // w/o having to forcefully move to a new result type
+
+        try {
+          setSQLGroupByInAggregationResults(brokerResponseNative, dataSchema, dataTables, reducerContext);
+        } catch (TimeoutException e) {
+          brokerResponseNative.getProcessingExceptions()
+              .add(new QueryProcessingException(QueryException.BROKER_TIMEOUT_ERROR_CODE, e.getMessage()));
+        }
+
+        if (!brokerResponseNative.getAggregationResults().isEmpty()) {
+          resultSize = brokerResponseNative.getAggregationResults().get(0).getGroupByResult().size();
+        }
+      }
+    } else {
+
+      // 3. groupByMode = pql, responseFormat = sql
+      // This mode is for users who want response presented in SQL style, but want PQL style group by behavior
+      // Multiple aggregations in PQL violates the tabular nature of results
+      // As a result, in this mode, only single aggregations are supported
+
+      // 4. groupByMode = pql, responseFormat = pql
+      // This is the primary PQL compliant group by
+
+      setGroupByResults(brokerResponseNative, dataTables);
+
+      if (_responseFormatSql) {
+        resultSize = brokerResponseNative.getResultTable().getRows().size();
+      } else {
+        // We emit the group by size when the result isn't empty. All the sizes among group-by results should be the
+        // same.
+        // Thus, we can just emit the one from the 1st result.
+        if (!brokerResponseNative.getAggregationResults().isEmpty()) {
+          resultSize = brokerResponseNative.getAggregationResults().get(0).getGroupByResult().size();
+        }
+      }
+    }
+
+    if (brokerMetrics != null && resultSize > 0) {
+      brokerMetrics.addMeteredTableValue(tableName, BrokerMeter.GROUP_BY_SIZE, resultSize);
+    }
+  }
+
+  private Key constructKey(Object[] row) {
+    Object [] keyColumns = new Object[_numOfKeyColumns];
+    for (int i = 0; i < _numOfKeyColumns; i++) {
+      keyColumns[i] = row[i + 1];
+    }
+    return new Key(keyColumns);

Review comment:
       Done




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