Yes, you can do in mongo-river.you need to specify exclude fields in river mapping.. i ve attached a sample code.. check it out..
curl -XPUT 'http://IP:9200/_river/mongodb/_meta' -d '{
"type": "mongodb",
"mongodb": {
"db": "DATABASE_NAME",
"collection": "COLLECTION",
"gridfs": true
}, "options": {
"secondary_read_preference" : true,
"drop_collection": ${mongo.drop.collection},
"exclude_fields": ${mongo.exclude.fields},
"include_fields": ${mongo.include.fields},
"include_collection": ${mongo.include.collection},
"import_all_collections": ${mongo.import.all.collections},
"initial_timestamp": {
"script_type": ${mongo.initial.timestamp.script.type},
"script": ${mongo.initial.timestamp.script}
},
"skip_initial_import" : ${mongo.skip.initial.import},
"store_statistics" : ${mongo.store.statistics},
},
"index": {
"name": "ES_INDEX_NAME",
"type": "ES_TYPE_NAME"
}
}'
for more information refer: https://github.com/richardwilly98/elasticsearch-river-mongodb/wiki
HOpe it helps..!