io.druid.segment.filter.ExpressionFilter.java Source code

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Here is the source code for io.druid.segment.filter.ExpressionFilter.java

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/*
 * Licensed to Metamarkets Group Inc. (Metamarkets) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. Metamarkets 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 io.druid.segment.filter;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterables;
import io.druid.math.expr.Evals;
import io.druid.math.expr.Expr;
import io.druid.math.expr.Parser;
import io.druid.query.BitmapResultFactory;
import io.druid.query.expression.ExprUtils;
import io.druid.query.filter.BitmapIndexSelector;
import io.druid.query.filter.Filter;
import io.druid.query.filter.ValueMatcher;
import io.druid.query.monomorphicprocessing.RuntimeShapeInspector;
import io.druid.segment.ColumnSelector;
import io.druid.segment.ColumnSelectorFactory;
import io.druid.segment.ColumnValueSelector;
import io.druid.segment.virtual.ExpressionSelectors;

import java.util.Set;

public class ExpressionFilter implements Filter {
    private final Expr expr;
    private final Set<String> requiredBindings;

    public ExpressionFilter(final Expr expr) {
        this.expr = expr;
        this.requiredBindings = ImmutableSet.copyOf(Parser.findRequiredBindings(expr));
    }

    @Override
    public ValueMatcher makeMatcher(final ColumnSelectorFactory factory) {
        final ColumnValueSelector selector = ExpressionSelectors.makeColumnValueSelector(factory, expr);
        return new ValueMatcher() {
            @Override
            public boolean matches() {
                return Evals.asBoolean(selector.getLong());
            }

            @Override
            public void inspectRuntimeShape(final RuntimeShapeInspector inspector) {
                inspector.visit("selector", selector);
            }
        };
    }

    @Override
    public boolean supportsBitmapIndex(final BitmapIndexSelector selector) {
        if (requiredBindings.isEmpty()) {
            // Constant expression.
            return true;
        } else if (requiredBindings.size() == 1) {
            // Single-column expression. We can use bitmap indexes if this column has an index and does not have
            // multiple values. The lack of multiple values is important because expression filters treat multi-value
            // arrays as nulls, which doesn't permit index based filtering.
            final String column = Iterables.getOnlyElement(requiredBindings);
            return selector.getBitmapIndex(column) != null && !selector.hasMultipleValues(column);
        } else {
            // Multi-column expression.
            return false;
        }
    }

    @Override
    public <T> T getBitmapResult(final BitmapIndexSelector selector,
            final BitmapResultFactory<T> bitmapResultFactory) {
        if (requiredBindings.isEmpty()) {
            // Constant expression.
            if (expr.eval(ExprUtils.nilBindings()).asBoolean()) {
                return bitmapResultFactory.wrapAllTrue(Filters.allTrue(selector));
            } else {
                return bitmapResultFactory.wrapAllFalse(Filters.allFalse(selector));
            }
        } else {
            // Can assume there's only one binding and it has a bitmap index, otherwise supportsBitmapIndex would have
            // returned false and the caller should not have called us.
            final String column = Iterables.getOnlyElement(requiredBindings);
            return Filters.matchPredicate(column, selector, bitmapResultFactory,
                    value -> expr.eval(identifierName -> {
                        // There's only one binding, and it must be the single column, so it can safely be ignored in production.
                        assert column.equals(identifierName);
                        return value;
                    }).asBoolean());
        }
    }

    @Override
    public boolean supportsSelectivityEstimation(final ColumnSelector columnSelector,
            final BitmapIndexSelector indexSelector) {
        return false;
    }

    @Override
    public double estimateSelectivity(final BitmapIndexSelector indexSelector) {
        // Selectivity estimation not supported.
        throw new UnsupportedOperationException();
    }
}