| /* |
| * 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; |
| |
| import com.google.common.base.Preconditions; |
| import com.google.common.base.Predicate; |
| import org.apache.druid.query.extraction.ExtractionFn; |
| import org.apache.druid.query.filter.ValueMatcher; |
| import org.apache.druid.query.monomorphicprocessing.RuntimeShapeInspector; |
| import org.apache.druid.segment.data.IndexedInts; |
| import org.apache.druid.segment.data.SingleIndexedInt; |
| |
| import javax.annotation.Nullable; |
| import java.util.ArrayList; |
| import java.util.List; |
| import java.util.Objects; |
| |
| /** |
| * A special {@link DimensionSelector} for projected time columns |
| * - it assumes time values are scanned once and values are grouped together |
| * (i.e. we never revisit a timestamp we have seen before, unless it is the same as the last accessed one) |
| * - it also applies and caches extraction function values at the {@link DimensionSelector} level to speed things up |
| */ |
| public class SingleScanTimeDimensionSelector implements DimensionSelector |
| { |
| private final ExtractionFn extractionFn; |
| private final BaseLongColumnValueSelector selector; |
| private final boolean descending; |
| |
| private final List<String> timeValues = new ArrayList<>(); |
| private final SingleIndexedInt row = new SingleIndexedInt(); |
| private long currentTimestamp = Long.MIN_VALUE; |
| private int index = -1; |
| |
| @Nullable |
| private String currentValue = null; |
| |
| public SingleScanTimeDimensionSelector( |
| BaseLongColumnValueSelector selector, |
| @Nullable ExtractionFn extractionFn, |
| boolean descending |
| ) |
| { |
| Preconditions.checkNotNull(extractionFn, "time dimension must provide an extraction function"); |
| this.extractionFn = extractionFn; |
| this.selector = selector; |
| this.descending = descending; |
| } |
| |
| @Override |
| public IndexedInts getRow() |
| { |
| row.setValue(getDimensionValueIndex()); |
| return row; |
| } |
| |
| @Override |
| public ValueMatcher makeValueMatcher(final @Nullable String value) |
| { |
| return new ValueMatcher() |
| { |
| @Override |
| public boolean matches() |
| { |
| return Objects.equals(lookupName(getDimensionValueIndex()), value); |
| } |
| |
| @Override |
| public void inspectRuntimeShape(RuntimeShapeInspector inspector) |
| { |
| inspector.visit("selector", SingleScanTimeDimensionSelector.this); |
| } |
| }; |
| } |
| |
| @Override |
| public ValueMatcher makeValueMatcher(final Predicate<String> predicate) |
| { |
| return new ValueMatcher() |
| { |
| @Override |
| public boolean matches() |
| { |
| return predicate.apply(lookupName(getDimensionValueIndex())); |
| } |
| |
| @Override |
| public void inspectRuntimeShape(RuntimeShapeInspector inspector) |
| { |
| inspector.visit("selector", SingleScanTimeDimensionSelector.this); |
| inspector.visit("predicate", predicate); |
| } |
| }; |
| } |
| |
| private int getDimensionValueIndex() |
| { |
| // if this the first timestamp, apply and cache extraction function result |
| final long timestamp = selector.getLong(); |
| if (index < 0) { |
| currentTimestamp = timestamp; |
| currentValue = extractionFn.apply(timestamp); |
| ++index; |
| timeValues.add(currentValue); |
| // if this is a new timestamp, apply and cache extraction function result |
| // since timestamps are assumed grouped and scanned once, we only need to |
| // check if the current timestamp is different than the current timestamp. |
| // |
| // If this new timestamp is mapped to the same value by the extraction function, |
| // we can also avoid creating a dimension value and corresponding index |
| // and use the current one |
| } else if (timestamp != currentTimestamp) { |
| if (descending ? timestamp > currentTimestamp : timestamp < currentTimestamp) { |
| // re-using this selector for multiple scans would cause the same rows to return different IDs |
| // we might want to re-visit if we ever need to do multiple scans with this dimension selector |
| throw new IllegalStateException("cannot re-use time dimension selector for multiple scans"); |
| } |
| currentTimestamp = timestamp; |
| final String value = extractionFn.apply(timestamp); |
| if (!Objects.equals(value, currentValue)) { |
| currentValue = value; |
| ++index; |
| timeValues.add(currentValue); |
| } |
| // Note: this could be further optimized by checking if the new value is one we have |
| // previously seen, but would require keeping track of both the current and the maximum index |
| } |
| // otherwise, if the current timestamp is the same as the previous timestamp, |
| // keep using the same dimension value index |
| |
| return index; |
| } |
| |
| @Override |
| public int getValueCardinality() |
| { |
| return Integer.MAX_VALUE; |
| } |
| |
| @Override |
| public String lookupName(int id) |
| { |
| if (id == index) { |
| return currentValue; |
| } else { |
| return timeValues.get(id); |
| } |
| } |
| |
| @Override |
| public boolean nameLookupPossibleInAdvance() |
| { |
| return false; |
| } |
| |
| @Nullable |
| @Override |
| public IdLookup idLookup() |
| { |
| return null; |
| } |
| |
| @Nullable |
| @Override |
| public String getObject() |
| { |
| return currentValue; |
| } |
| |
| @Override |
| public Class<String> classOfObject() |
| { |
| return String.class; |
| } |
| |
| @Override |
| public void inspectRuntimeShape(RuntimeShapeInspector inspector) |
| { |
| inspector.visit("selector", selector); |
| inspector.visit("extractionFn", extractionFn); |
| inspector.visit("descending", descending); |
| } |
| } |