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Indexes: Indexing Counters
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To index counters, create a static index that inherits from
AbstractCountersIndexCreationTask. -
Auto-indexes for counters are not available at this time.
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In this page:
Syntax
In order to index counter values, create an index that inherits from AbstractCountersIndexCreationTask.
Next, choose one of these two methods which take the index expression:
protected void addMap(String map)addMap only indexes the counters with
the specified name.
Examples of indexes using the method:
public static class MyCounterIndex extends AbstractCountersIndexCreationTask {
public MyCounterIndex() {
map = "counters.Companies.HeartRate.Select(counter => new {\n" +
" heartBeat = counter.Value,\n" +
" name = counter.Name,\n" +
" user = counter.DocumentId\n" +
"})";
}
}CounterNamesFor
While indexes inheriting from AbstractIndexCreationTask cannot index counter values, the counterNamesFor()
method is available which returns the names of all counters for a specified document:
List<String> CounterNamesFor(Object doc);Example of index using counterNamesFor():
public static class Companies_ByCounterNames extends AbstractIndexCreationTask {
public Companies_ByCounterNames() {
map = "from e in docs.Employees\n" +
"let counterNames = CounterNamesFor(e)\n" +
"select new\n" +
"{\n" +
" counterNames = counterNames.ToArray()\n" +
"}";
}
}Querying the Index
// return all companies that have 'Likes' counter
List<Company> companies = session
.query(Company.class, Companies_ByCounterNames.class)
.containsAny("counterNames", Lists.newArrayList("Likes"))
.toList();
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