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The date_histogram accepts an interval which can be either a calendar interval (DST-aware, leap seconds, arbitrary length of months, etc) or fixed interval (strict multiples of SI units). Unfortunately this is inferred by first trying to parse as a calendar interval, then falling back to fixed if that fails. This leads to confusing arrangement where `1d` == calendar, but `2d` == fixed. And if you want a day of fixed time, you have to specify `24h` (e.g. the next smallest unit). This arrangement is very error-prone for users. This PR adds `calendar_interval` and `fixed_interval` parameters to any code that uses intervals (date_histogram, rollup, composite, datafeed, etc). Calendar only accepts calendar intervals, fixed accepts any combination of units (meaning `1d` can be used to specify `24h` in fixed time), and both are mutually exclusive. The old interval behavior is deprecated and will throw a deprecation warning. It is also mutually exclusive with the two new parameters. In the future the old dual-purpose interval will be removed. The change applies to both REST and java clients.
74 lines
2.4 KiB
Plaintext
74 lines
2.4 KiB
Plaintext
[[java-aggs-bucket-datehistogram]]
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==== Date Histogram Aggregation
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Here is how you can use
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{ref}/search-aggregations-bucket-datehistogram-aggregation.html[Date Histogram Aggregation]
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with Java API.
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===== Prepare aggregation request
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Here is an example on how to create the aggregation request:
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[source,java]
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--------------------------------------------------
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AggregationBuilder aggregation =
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AggregationBuilders
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.dateHistogram("agg")
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.field("dateOfBirth")
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.calendarInterval(DateHistogramInterval.YEAR);
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--------------------------------------------------
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Or if you want to set an interval of 10 days:
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[source,java]
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--------------------------------------------------
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AggregationBuilder aggregation =
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AggregationBuilders
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.dateHistogram("agg")
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.field("dateOfBirth")
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.fixedInterval(DateHistogramInterval.days(10));
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--------------------------------------------------
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===== Use aggregation response
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Import Aggregation definition classes:
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[source,java]
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--------------------------------------------------
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import org.elasticsearch.search.aggregations.bucket.histogram.Histogram;
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--------------------------------------------------
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[source,java]
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--------------------------------------------------
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// sr is here your SearchResponse object
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Histogram agg = sr.getAggregations().get("agg");
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// For each entry
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for (Histogram.Bucket entry : agg.getBuckets()) {
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DateTime key = (DateTime) entry.getKey(); // Key
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String keyAsString = entry.getKeyAsString(); // Key as String
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long docCount = entry.getDocCount(); // Doc count
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logger.info("key [{}], date [{}], doc_count [{}]", keyAsString, key.getYear(), docCount);
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}
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--------------------------------------------------
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This will basically produce for the first example:
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[source,text]
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--------------------------------------------------
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key [1942-01-01T00:00:00.000Z], date [1942], doc_count [1]
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key [1945-01-01T00:00:00.000Z], date [1945], doc_count [1]
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key [1946-01-01T00:00:00.000Z], date [1946], doc_count [1]
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...
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key [2005-01-01T00:00:00.000Z], date [2005], doc_count [1]
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key [2007-01-01T00:00:00.000Z], date [2007], doc_count [2]
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key [2008-01-01T00:00:00.000Z], date [2008], doc_count [3]
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--------------------------------------------------
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===== Order
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Supports the same order functionality as the <<java-aggs-bucket-terms,`Terms Aggregation`>>.
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