Terms Facets with few hits got Elastic Out Of Memory Error.

gistfile1.txt

Java Version: jdk1.7.0_05
ElasticSearch Engine Version: elasticsearch-0.20.5
Cluster Info: We have one master node, and 2 slave nodes, with all :
              ES_HEAP_SIZE=3000M
              ES_MIN_MEM=3000M
              ES_MAX_MEM=3000M

On Master Node: ps aux | grep elas
root      1447  9.6 45.0 3840652 3679364 ?     SLl  Mar07 138:52 /root/jdk1.7.0_05/bin/java -Xms3000M -Xmx3000M -Xss256k -Djava.awt.headless=true -XX:+UseParNewGC -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=75 -XX:+UseCMSInitiatingOccupancyOnly -XX:+HeapDumpOnOutOfMemoryError -Delasticsearch -Des.path.home=/root/elasticsearch-0.20.5 -cp :/root/elasticsearch-0.20.5/lib/elasticsearch-0.20.5.jar:/root/elasticsearch-0.20.5/lib/*:/root/elasticsearch-0.20.5/lib/sigar/* org.elasticsearch.bootstrap.ElasticSearch

Index name: surfikisemterms
the mapping is:
{"surfikisemterms":{"jdbc_search":{"properties":{"facets":{"dynamic":"true","properties":{"termscount":{"dynamic":"true","properties":{"terms":{"dynamic":"true","properties":{"field":{"type":"string"},"size":{"type":"long"}}}}}}},"from":{"type":"long"},"query":{"dynamic":"true","properties":{"bool":{"dynamic":"true","properties":{"must":{"dynamic":"true","properties":{"query_string":{"dynamic":"true","properties":{"query":{"type":"string"}}}}}}}}},"size":{"type":"long"}}},"jdbc":{"properties":{"keywords":{"type":"string","analyzer":"comma"},"time":{"type":"date","format":"dateOptionalTime"}}}}}

index setting is:
{"surfikisemterms":{"settings":{"index.analysis.tokenizer.commatokenizer.type":"pattern","index.analysis.analyzer.comma.type":"custom","index.number_of_replicas":"1","index.version.created":"200599","index.analysis.tokenizer.commatokenizer.pattern":",","index.analysis.analyzer.comma.tokenizer":"commatokenizer","index.number_of_shards":"5"}}}

So actually we have 2 fields in the surfikisemterms,
1. keywords, a list of string
2. time, the timestamp for these keywords

The query:
{ 
 "query": { 
   "bool": { 
     "must": [ 
       { 
         "range": { 
           "time": { 
             "from": "2013-03-07T11:29:19.000Z", 
             "to": "2013-03-07T11:30:19.000Z" 
           } 
         } 
       } 
     ], 
     "must_not": [], 
     "should": [] 
   } 
 }, 
 "from": 0, 
 "size": 10, 
 "sort": [], 
 "facets": {} 
}

Above query will return about 20 hits, with each hit the keyword list will no more than 20.

So, the terms facets according to above query:

Then if I do: 
{ 
 "query": { 
   "bool": { 
     "must": [ 
       { 
         "range": { 
           "time": { 
             "from": "2013-03-07T11:29:19.000Z", 
             "to": "2013-03-07T11:30:19.000Z" 
           } 
         } 
       } 
     ], 
     "must_not": [], 
     "should": [] 
   } 
 }, 
 "from": 0, 
 "size": 22, 
 "sort": [], 
 "facets": { 
   "termscount": { 
     "terms": { 
       "field": "keywords", 
       "size": 25 
     } 
   } 
 } 
} 
I can see following logs (on master node, name is Bobby Hutcherson) repeating for several time: 

[2013-03-08 03:31:05,571][WARN ][index.cache.field.data.resident] [Surfiki 
Master: Bobby Hutcherson] [surfikisemterms] loading field [keywords] caused 
out of memory failure 
java.lang.OutOfMemoryError: Java heap space..

Thanks.