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 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch 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
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package org.elasticsearch.search.aggregations.pipeline;

import org.elasticsearch.action.index.IndexRequestBuilder;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.index.mapper.DateFieldMapper;
import org.elasticsearch.search.aggregations.InternalAggregation;
import org.elasticsearch.search.aggregations.InternalMultiBucketAggregation;
import org.elasticsearch.search.aggregations.bucket.histogram.DateHistogramInterval;
import org.elasticsearch.search.aggregations.bucket.histogram.Histogram;
import org.elasticsearch.search.aggregations.bucket.histogram.Histogram.Bucket;
import org.elasticsearch.search.aggregations.metrics.sum.Sum;
import org.elasticsearch.search.aggregations.pipeline.derivative.Derivative;
import org.elasticsearch.search.aggregations.support.AggregationPath;
import org.elasticsearch.test.ESIntegTestCase;
import org.hamcrest.Matcher;
import org.joda.time.DateTime;
import org.joda.time.DateTimeZone;
import org.joda.time.format.DateTimeFormat;
import org.junit.After;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import static org.elasticsearch.common.xcontent.XContentFactory.jsonBuilder;
import static org.elasticsearch.search.aggregations.AggregationBuilders.dateHistogram;
import static org.elasticsearch.search.aggregations.AggregationBuilders.sum;
import static org.elasticsearch.search.aggregations.pipeline.PipelineAggregatorBuilders.derivative;
import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertSearchResponse;
import static org.hamcrest.Matchers.closeTo;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.is;
import static org.hamcrest.core.IsNull.notNullValue;
import static org.hamcrest.core.IsNull.nullValue;

@ESIntegTestCase.SuiteScopeTestCase
public class DateDerivativeIT extends ESIntegTestCase {

    // some index names used during these tests
    private static final String IDX_DST_START = "idx_dst_start";
    private static final String IDX_DST_END = "idx_dst_end";
    private static final String IDX_DST_KATHMANDU = "idx_dst_kathmandu";

    private DateTime date(int month, int day) {
        return new DateTime(2012, month, day, 0, 0, DateTimeZone.UTC);
    }

    private DateTime date(String date) {
        return DateFieldMapper.DEFAULT_DATE_TIME_FORMATTER.parser().parseDateTime(date);
    }

    private static String format(DateTime date, String pattern) {
        return DateTimeFormat.forPattern(pattern).print(date);
    }

    private static IndexRequestBuilder indexDoc(String idx, DateTime date, int value) throws Exception {
        return client().prepareIndex(idx, "type").setSource(
                jsonBuilder().startObject().field("date", date).field("value", value).endObject());
    }

    private IndexRequestBuilder indexDoc(int month, int day, int value) throws Exception {
        return client().prepareIndex("idx", "type").setSource(
                jsonBuilder().startObject().field("value", value).field("date", date(month, day)).startArray("dates")
                        .value(date(month, day)).value(date(month + 1, day + 1)).endArray().endObject());
    }

    @Override
    public void setupSuiteScopeCluster() throws Exception {
        createIndex("idx");
        createIndex("idx_unmapped");
        // TODO: would be nice to have more random data here
        prepareCreate("empty_bucket_idx").addMapping("type", "value", "type=integer").execute().actionGet();
        List<IndexRequestBuilder> builders = new ArrayList<>();
        for (int i = 0; i < 2; i++) {
            builders.add(client().prepareIndex("empty_bucket_idx", "type", "" + i).setSource(
                    jsonBuilder().startObject().field("value", i * 2).endObject()));
        }
        builders.addAll(Arrays.asList(indexDoc(1, 2, 1), // date: Jan 2, dates: Jan 2, Feb 3
                indexDoc(2, 2, 2), // date: Feb 2, dates: Feb 2, Mar 3
                indexDoc(2, 15, 3), // date: Feb 15, dates: Feb 15, Mar 16
                indexDoc(3, 2, 4), // date: Mar 2, dates: Mar 2, Apr 3
                indexDoc(3, 15, 5), // date: Mar 15, dates: Mar 15, Apr 16
                indexDoc(3, 23, 6))); // date: Mar 23, dates: Mar 23, Apr 24
        indexRandom(true, builders);
        ensureSearchable();
    }

    @After
    public void afterEachTest() throws IOException {
        internalCluster().wipeIndices(IDX_DST_START, IDX_DST_END, IDX_DST_KATHMANDU);
    }

    public void testSingleValuedField() throws Exception {
        SearchResponse response = client()
                .prepareSearch("idx")
                .addAggregation(
                        dateHistogram("histo").field("date").dateHistogramInterval(DateHistogramInterval.MONTH).minDocCount(0)
                                .subAggregation(derivative("deriv", "_count"))).execute().actionGet();

        assertSearchResponse(response);

        Histogram deriv = response.getAggregations().get("histo");
        assertThat(deriv, notNullValue());
        assertThat(deriv.getName(), equalTo("histo"));
        List<? extends Bucket> buckets = deriv.getBuckets();
        assertThat(buckets.size(), equalTo(3));

        DateTime key = new DateTime(2012, 1, 1, 0, 0, DateTimeZone.UTC);
        Histogram.Bucket bucket = buckets.get(0);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(1L));
        SimpleValue docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, nullValue());

        key = new DateTime(2012, 2, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(1);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(2L));
        docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, notNullValue());
        assertThat(docCountDeriv.value(), equalTo(1d));

        key = new DateTime(2012, 3, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(2);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(3L));
        docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, notNullValue());
        assertThat(docCountDeriv.value(), equalTo(1d));
    }

    public void testSingleValuedFieldNormalised() throws Exception {
        SearchResponse response = client()
                .prepareSearch("idx")
                .addAggregation(
                        dateHistogram("histo").field("date").dateHistogramInterval(DateHistogramInterval.MONTH).minDocCount(0)
                                .subAggregation(derivative("deriv", "_count").unit(DateHistogramInterval.DAY))).execute()
                .actionGet();

        assertSearchResponse(response);

        Histogram deriv = response.getAggregations().get("histo");
        assertThat(deriv, notNullValue());
        assertThat(deriv.getName(), equalTo("histo"));
        List<? extends Bucket> buckets = deriv.getBuckets();
        assertThat(buckets.size(), equalTo(3));

        DateTime key = new DateTime(2012, 1, 1, 0, 0, DateTimeZone.UTC);
        Histogram.Bucket bucket = buckets.get(0);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(1L));
        Derivative docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, nullValue());

        key = new DateTime(2012, 2, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(1);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(2L));
        docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, notNullValue());
        assertThat(docCountDeriv.value(), closeTo(1d, 0.00001));
        assertThat(docCountDeriv.normalizedValue(), closeTo(1d / 31d, 0.00001));

        key = new DateTime(2012, 3, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(2);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(3L));
        docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, notNullValue());
        assertThat(docCountDeriv.value(), closeTo(1d, 0.00001));
        assertThat(docCountDeriv.normalizedValue(), closeTo(1d / 29d, 0.00001));
    }

    /**
     * Do a derivative on a date histogram with time zone CET at DST start
     */
    public void testSingleValuedFieldNormalised_timeZone_CET_DstStart() throws Exception {
        createIndex(IDX_DST_START);
        List<IndexRequestBuilder> builders = new ArrayList<>();

        DateTimeZone timezone = DateTimeZone.forID("CET");
        addNTimes(1, IDX_DST_START, new DateTime("2012-03-24T01:00:00", timezone), builders);
        addNTimes(2, IDX_DST_START, new DateTime("2012-03-25T01:00:00", timezone), builders); // day with dst shift, only 23h long
        addNTimes(3, IDX_DST_START, new DateTime("2012-03-26T01:00:00", timezone), builders);
        addNTimes(4, IDX_DST_START, new DateTime("2012-03-27T01:00:00", timezone), builders);
        indexRandom(true, builders);
        ensureSearchable();

        SearchResponse response = client()
                .prepareSearch(IDX_DST_START)
                .addAggregation(dateHistogram("histo").field("date").dateHistogramInterval(DateHistogramInterval.DAY)
                        .timeZone(timezone).minDocCount(0)
                        .subAggregation(derivative("deriv", "_count").unit(DateHistogramInterval.HOUR)))
                .execute()
                .actionGet();

        assertSearchResponse(response);

        Histogram deriv = response.getAggregations().get("histo");
        assertThat(deriv, notNullValue());
        assertThat(deriv.getName(), equalTo("histo"));
        List<? extends Bucket> buckets = deriv.getBuckets();
        assertThat(buckets.size(), equalTo(4));

        assertBucket(buckets.get(0), new DateTime("2012-03-24", timezone).toDateTime(DateTimeZone.UTC), 1L, nullValue(), null, null);
        assertBucket(buckets.get(1), new DateTime("2012-03-25", timezone).toDateTime(DateTimeZone.UTC), 2L, notNullValue(), 1d, 1d / 24d);
        // the following is normalized using a 23h bucket width
        assertBucket(buckets.get(2), new DateTime("2012-03-26", timezone).toDateTime(DateTimeZone.UTC), 3L, notNullValue(), 1d, 1d / 23d);
        assertBucket(buckets.get(3), new DateTime("2012-03-27", timezone).toDateTime(DateTimeZone.UTC), 4L, notNullValue(), 1d, 1d / 24d);
    }

    /**
     * Do a derivative on a date histogram with time zone CET at DST end
     */
    public void testSingleValuedFieldNormalised_timeZone_CET_DstEnd() throws Exception {
        createIndex(IDX_DST_END);
        DateTimeZone timezone = DateTimeZone.forID("CET");
        List<IndexRequestBuilder> builders = new ArrayList<>();

        addNTimes(1, IDX_DST_END, new DateTime("2012-10-27T01:00:00", timezone), builders);
        addNTimes(2, IDX_DST_END, new DateTime("2012-10-28T01:00:00", timezone), builders); // day with dst shift -1h, 25h long
        addNTimes(3, IDX_DST_END, new DateTime("2012-10-29T01:00:00", timezone), builders);
        addNTimes(4, IDX_DST_END, new DateTime("2012-10-30T01:00:00", timezone), builders);
        indexRandom(true, builders);
        ensureSearchable();

        SearchResponse response = client()
                .prepareSearch(IDX_DST_END)
                .addAggregation(dateHistogram("histo").field("date").dateHistogramInterval(DateHistogramInterval.DAY)
                        .timeZone(timezone).minDocCount(0)
                        .subAggregation(derivative("deriv", "_count").unit(DateHistogramInterval.HOUR)))
                .execute()
                .actionGet();

        assertSearchResponse(response);

        Histogram deriv = response.getAggregations().get("histo");
        assertThat(deriv, notNullValue());
        assertThat(deriv.getName(), equalTo("histo"));
        List<? extends Bucket> buckets = deriv.getBuckets();
        assertThat(buckets.size(), equalTo(4));

        assertBucket(buckets.get(0), new DateTime("2012-10-27", timezone).toDateTime(DateTimeZone.UTC), 1L, nullValue(), null, null);
        assertBucket(buckets.get(1), new DateTime("2012-10-28", timezone).toDateTime(DateTimeZone.UTC), 2L, notNullValue(), 1d, 1d / 24d);
        // the following is normalized using a 25h bucket width
        assertBucket(buckets.get(2), new DateTime("2012-10-29", timezone).toDateTime(DateTimeZone.UTC), 3L, notNullValue(), 1d, 1d / 25d);
        assertBucket(buckets.get(3), new DateTime("2012-10-30", timezone).toDateTime(DateTimeZone.UTC), 4L, notNullValue(), 1d, 1d / 24d);
    }

    /**
     * also check for time zone shifts that are not one hour, e.g.
     * "Asia/Kathmandu, 1 Jan 1986 - Time Zone Change (IST → NPT), at 00:00:00 clocks were turned forward 00:15 minutes
     */
    public void testSingleValuedFieldNormalised_timeZone_AsiaKathmandu() throws Exception {
        createIndex(IDX_DST_KATHMANDU);
        DateTimeZone timezone = DateTimeZone.forID("Asia/Kathmandu");
        List<IndexRequestBuilder> builders = new ArrayList<>();

        addNTimes(1, IDX_DST_KATHMANDU, new DateTime("1985-12-31T22:30:00", timezone), builders);
        // the shift happens during the next bucket, which includes the 45min that do not start on the full hour
        addNTimes(2, IDX_DST_KATHMANDU, new DateTime("1985-12-31T23:30:00", timezone), builders);
        addNTimes(3, IDX_DST_KATHMANDU, new DateTime("1986-01-01T01:30:00", timezone), builders);
        addNTimes(4, IDX_DST_KATHMANDU, new DateTime("1986-01-01T02:30:00", timezone), builders);
        indexRandom(true, builders);
        ensureSearchable();

        SearchResponse response = client()
                .prepareSearch(IDX_DST_KATHMANDU)
                .addAggregation(dateHistogram("histo").field("date").dateHistogramInterval(DateHistogramInterval.HOUR)
                        .timeZone(timezone).minDocCount(0)
                        .subAggregation(derivative("deriv", "_count").unit(DateHistogramInterval.MINUTE)))
                .execute()
                .actionGet();

        assertSearchResponse(response);

        Histogram deriv = response.getAggregations().get("histo");
        assertThat(deriv, notNullValue());
        assertThat(deriv.getName(), equalTo("histo"));
        List<? extends Bucket> buckets = deriv.getBuckets();
        assertThat(buckets.size(), equalTo(4));

        assertBucket(buckets.get(0), new DateTime("1985-12-31T22:00:00", timezone).toDateTime(DateTimeZone.UTC), 1L, nullValue(), null,
                null);
        assertBucket(buckets.get(1), new DateTime("1985-12-31T23:00:00", timezone).toDateTime(DateTimeZone.UTC), 2L, notNullValue(), 1d,
                1d / 60d);
        // the following is normalized using a 105min bucket width
        assertBucket(buckets.get(2), new DateTime("1986-01-01T01:00:00", timezone).toDateTime(DateTimeZone.UTC), 3L, notNullValue(), 1d,
                1d / 105d);
        assertBucket(buckets.get(3), new DateTime("1986-01-01T02:00:00", timezone).toDateTime(DateTimeZone.UTC), 4L, notNullValue(), 1d,
                1d / 60d);
    }

    private static void addNTimes(int amount, String index, DateTime dateTime, List<IndexRequestBuilder> builders) throws Exception {
        for (int i = 0; i < amount; i++) {
            builders.add(indexDoc(index, dateTime, 1));
        }
    }

    private static void assertBucket(Histogram.Bucket bucket, DateTime expectedKey, long expectedDocCount,
            Matcher<Object> derivativeMatcher, Double derivative, Double normalizedDerivative) {
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(expectedKey));
        assertThat(bucket.getDocCount(), equalTo(expectedDocCount));
        Derivative docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, derivativeMatcher);
        if (docCountDeriv != null) {
            assertThat(docCountDeriv.value(), closeTo(derivative, 0.00001));
            assertThat(docCountDeriv.normalizedValue(), closeTo(normalizedDerivative, 0.00001));
        }
    }

    public void testSingleValuedFieldWithSubAggregation() throws Exception {
        SearchResponse response = client()
                .prepareSearch("idx")
                .addAggregation(
                        dateHistogram("histo").field("date").dateHistogramInterval(DateHistogramInterval.MONTH).minDocCount(0)
                            .subAggregation(sum("sum").field("value")).subAggregation(derivative("deriv", "sum")))
                .execute().actionGet();

        assertSearchResponse(response);

        Histogram histo = response.getAggregations().get("histo");
        assertThat(histo, notNullValue());
        assertThat(histo.getName(), equalTo("histo"));
        List<? extends Bucket> buckets = histo.getBuckets();
        assertThat(buckets.size(), equalTo(3));
        Object[] propertiesKeys = (Object[]) ((InternalAggregation)histo).getProperty("_key");
        Object[] propertiesDocCounts = (Object[]) ((InternalAggregation)histo).getProperty("_count");
        Object[] propertiesCounts = (Object[]) ((InternalAggregation)histo).getProperty("sum.value");

        DateTime key = new DateTime(2012, 1, 1, 0, 0, DateTimeZone.UTC);
        Histogram.Bucket bucket = buckets.get(0);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(1L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(false));
        Sum sum = bucket.getAggregations().get("sum");
        assertThat(sum, notNullValue());
        assertThat(sum.getValue(), equalTo(1.0));
        SimpleValue deriv = bucket.getAggregations().get("deriv");
        assertThat(deriv, nullValue());
        assertThat((DateTime) propertiesKeys[0], equalTo(key));
        assertThat((long) propertiesDocCounts[0], equalTo(1L));
        assertThat((double) propertiesCounts[0], equalTo(1.0));

        key = new DateTime(2012, 2, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(1);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(2L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(false));
        sum = bucket.getAggregations().get("sum");
        assertThat(sum, notNullValue());
        assertThat(sum.getValue(), equalTo(5.0));
        deriv = bucket.getAggregations().get("deriv");
        assertThat(deriv, notNullValue());
        assertThat(deriv.value(), equalTo(4.0));
        assertThat(((InternalMultiBucketAggregation.InternalBucket)bucket).getProperty(
                "histo", AggregationPath.parse("deriv.value").getPathElementsAsStringList()), equalTo(4.0));
        assertThat((DateTime) propertiesKeys[1], equalTo(key));
        assertThat((long) propertiesDocCounts[1], equalTo(2L));
        assertThat((double) propertiesCounts[1], equalTo(5.0));

        key = new DateTime(2012, 3, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(2);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(3L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(false));
        sum = bucket.getAggregations().get("sum");
        assertThat(sum, notNullValue());
        assertThat(sum.getValue(), equalTo(15.0));
        deriv = bucket.getAggregations().get("deriv");
        assertThat(deriv, notNullValue());
        assertThat(deriv.value(), equalTo(10.0));
        assertThat(((InternalMultiBucketAggregation.InternalBucket)bucket).getProperty(
                "histo", AggregationPath.parse("deriv.value").getPathElementsAsStringList()), equalTo(10.0));
        assertThat((DateTime) propertiesKeys[2], equalTo(key));
        assertThat((long) propertiesDocCounts[2], equalTo(3L));
        assertThat((double) propertiesCounts[2], equalTo(15.0));
    }

    public void testMultiValuedField() throws Exception {
        SearchResponse response = client()
                .prepareSearch("idx")
                .addAggregation(
                        dateHistogram("histo").field("dates").dateHistogramInterval(DateHistogramInterval.MONTH).minDocCount(0)
                                .subAggregation(derivative("deriv", "_count"))).execute().actionGet();

        assertSearchResponse(response);

        Histogram deriv = response.getAggregations().get("histo");
        assertThat(deriv, notNullValue());
        assertThat(deriv.getName(), equalTo("histo"));
        List<? extends Bucket> buckets = deriv.getBuckets();
        assertThat(buckets.size(), equalTo(4));

        DateTime key = new DateTime(2012, 1, 1, 0, 0, DateTimeZone.UTC);
        Histogram.Bucket bucket = buckets.get(0);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(1L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(true));
        SimpleValue docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, nullValue());

        key = new DateTime(2012, 2, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(1);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(3L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(false));
        docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, notNullValue());
        assertThat(docCountDeriv.value(), equalTo(2.0));

        key = new DateTime(2012, 3, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(2);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(5L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(false));
        docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, notNullValue());
        assertThat(docCountDeriv.value(), equalTo(2.0));

        key = new DateTime(2012, 4, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(3);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(3L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(false));
        docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, notNullValue());
        assertThat(docCountDeriv.value(), equalTo(-2.0));
    }

    public void testUnmapped() throws Exception {
        SearchResponse response = client()
                .prepareSearch("idx_unmapped")
                .addAggregation(
                        dateHistogram("histo").field("date").dateHistogramInterval(DateHistogramInterval.MONTH).minDocCount(0)
                                .subAggregation(derivative("deriv", "_count"))).execute().actionGet();

        assertSearchResponse(response);

        Histogram deriv = response.getAggregations().get("histo");
        assertThat(deriv, notNullValue());
        assertThat(deriv.getName(), equalTo("histo"));
        assertThat(deriv.getBuckets().size(), equalTo(0));
    }

    public void testPartiallyUnmapped() throws Exception {
        SearchResponse response = client()
                .prepareSearch("idx", "idx_unmapped")
                .addAggregation(
                        dateHistogram("histo").field("date").dateHistogramInterval(DateHistogramInterval.MONTH).minDocCount(0)
                                .subAggregation(derivative("deriv", "_count"))).execute().actionGet();

        assertSearchResponse(response);

        Histogram deriv = response.getAggregations().get("histo");
        assertThat(deriv, notNullValue());
        assertThat(deriv.getName(), equalTo("histo"));
        List<? extends Bucket> buckets = deriv.getBuckets();
        assertThat(buckets.size(), equalTo(3));

        DateTime key = new DateTime(2012, 1, 1, 0, 0, DateTimeZone.UTC);
        Histogram.Bucket bucket = buckets.get(0);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(1L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(true));
        SimpleValue docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, nullValue());

        key = new DateTime(2012, 2, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(1);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(2L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(false));
        docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, notNullValue());
        assertThat(docCountDeriv.value(), equalTo(1.0));

        key = new DateTime(2012, 3, 1, 0, 0, DateTimeZone.UTC);
        bucket = buckets.get(2);
        assertThat(bucket, notNullValue());
        assertThat((DateTime) bucket.getKey(), equalTo(key));
        assertThat(bucket.getDocCount(), equalTo(3L));
        assertThat(bucket.getAggregations().asList().isEmpty(), is(false));
        docCountDeriv = bucket.getAggregations().get("deriv");
        assertThat(docCountDeriv, notNullValue());
        assertThat(docCountDeriv.value(), equalTo(1.0));
    }

}
