When I query，ES print：
org.elasticsearch.action.search.ReduceSearchPhaseException: Failed to execute phase [fetch], [reduce]
at org.elasticsearch.action.search.type.TransportSearchQueryThenFetchAction$AsyncAction.finishHim(TransportSearchQueryThenFetchAction.java:182)
at org.elasticsearch.action.search.type.TransportSearchQueryThenFetchAction$AsyncAction.moveToSecondPhase(TransportSearchQueryThenFetchAction.java:89)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction.innerMoveToSecondPhase(TransportSearchTypeAction.java:417)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction.onFirstPhaseResult(TransportSearchTypeAction.java:241)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction$3.onResult(TransportSearchTypeAction.java:219)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction$3.onResult(TransportSearchTypeAction.java:216)
at org.elasticsearch.search.action.SearchServiceTransportAction.sendExecuteQuery(SearchServiceTransportAction.java:203)
at org.elasticsearch.action.search.type.TransportSearchQueryThenFetchAction$AsyncAction.sendExecuteFirstPhase(TransportSearchQueryThenFetchAction.java:80)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction.performFirstPhase(TransportSearchTypeAction.java:216)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction.performFirstPhase(TransportSearchTypeAction.java:203)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction$2.run(TransportSearchTypeAction.java:186)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.OutOfMemoryError: Java heap space
at org.apache.lucene.util.ArrayUtil.grow(ArrayUtil.java:346)
at org.elasticsearch.common.io.stream.BytesStreamOutput.grow(BytesStreamOutput.java:110)
at org.elasticsearch.common.io.stream.BytesStreamOutput.writeBytes(BytesStreamOutput.java:99)
at org.elasticsearch.common.io.stream.StreamOutput.write(StreamOutput.java:311)
at org.elasticsearch.common.jackson.core.json.UTF8JsonGenerator._flushBuffer(UTF8JsonGenerator.java:1862)
at org.elasticsearch.common.jackson.core.json.UTF8JsonGenerator._writeBytes(UTF8JsonGenerator.java:1132)
at org.elasticsearch.common.jackson.core.json.UTF8JsonGenerator._writeFieldName(UTF8JsonGenerator.java:270)
at org.elasticsearch.common.jackson.core.json.UTF8JsonGenerator.writeFieldName(UTF8JsonGenerator.java:249)
at org.elasticsearch.common.xcontent.json.JsonXContentGenerator.writeFieldName(JsonXContentGenerator.java:86)
at org.elasticsearch.common.xcontent.XContentBuilder.field(XContentBuilder.java:242)
at org.elasticsearch.common.xcontent.XContentBuilder.field(XContentBuilder.java:409)
at org.elasticsearch.search.aggregations.metrics.stats.InternalStats.toXContent(InternalStats.java:195)
at org.elasticsearch.search.aggregations.InternalAggregations.toXContentInternal(InternalAggregations.java:184)
at org.elasticsearch.search.aggregations.bucket.terms.StringTerms.toXContent(StringTerms.java:137)
at org.elasticsearch.search.aggregations.InternalAggregations.toXContentInternal(InternalAggregations.java:184)
at org.elasticsearch.search.aggregations.bucket.terms.StringTerms.toXContent(StringTerms.java:137)
at org.elasticsearch.search.aggregations.InternalAggregations.toXContentInternal(InternalAggregations.java:184)
at org.elasticsearch.search.aggregations.InternalAggregations.toXContent(InternalAggregations.java:175)
at org.elasticsearch.search.internal.InternalSearchResponse.toXContent(InternalSearchResponse.java:93)
at org.elasticsearch.action.search.SearchResponse.toXContent(SearchResponse.java:217)
at org.elasticsearch.rest.action.search.RestSearchAction$1.onResponse(RestSearchAction.java:98)
at org.elasticsearch.rest.action.search.RestSearchAction$1.onResponse(RestSearchAction.java:92)
at org.elasticsearch.action.search.type.TransportSearchQueryThenFetchAction$AsyncAction.innerFinishHim(TransportSearchQueryThenFetchAction.java:198)
at org.elasticsearch.action.search.type.TransportSearchQueryThenFetchAction$AsyncAction.finishHim(TransportSearchQueryThenFetchAction.java:180)
at org.elasticsearch.action.search.type.TransportSearchQueryThenFetchAction$AsyncAction.moveToSecondPhase(TransportSearchQueryThenFetchAction.java:89)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction.innerMoveToSecondPhase(TransportSearchTypeAction.java:417)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction.onFirstPhaseResult(TransportSearchTypeAction.java:241)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction$3.onResult(TransportSearchTypeAction.java:219)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction$3.onResult(TransportSearchTypeAction.java:216)
at org.elasticsearch.search.action.SearchServiceTransportAction.sendExecuteQuery(SearchServiceTransportAction.java:203)
at org.elasticsearch.action.search.type.TransportSearchQueryThenFetchAction$AsyncAction.sendExecuteFirstPhase(TransportSearchQueryThenFetchAction.java:80)
at org.elasticsearch.action.search.type.TransportSearchTypeAction$BaseAsyncAction.performFirstPhase(TransportSearchTypeAction.java:216)
What is the reason? What better way?