Example that shows how applying a `match_all` `nested` query will exclude documents that do not have nested documents.

undesired-match-all-nested-behavior.sh

#!/bin/bash
#
# Description:
#   Example that shows how applying a `match_all` `nested` query will exclude hits that do not have nested documents. 
#   This may be related to ElasticSearch's `NestedQueryParser` and it's use of Lucene's `ToParentBlockJoinQuery`
#
# See:
#   - https://github.com/elasticsearch/elasticsearch/blob/0.90/src/main/java/org/elasticsearch/index/query/NestedQueryParser.java 
#   - http://lucene.apache.org/core/4_3_0/join/org/apache/lucene/search/join/package-summary.html 
#   - http://lucene.apache.org/core/4_3_0/join/org/apache/lucene/search/join/ToParentBlockJoinQuery.html

# Clean
curl -XDELETE http://localhost:9200/nested

# Create index 
curl -XPOST http://localhost:9200/nested

# Create nested mapping
curl -XPOST http://localhost:9200/nested/type/_mapping -d '
{
   "type":{
      "properties":{
         "list":{
            "type":"nested",
            "properties":{}
         }
      }
    }
}'

# Insert document with a nested doc
curl -XPOST http://localhost:9200/nested/type/ -d '
{
   "list":[
      { 
         x : 1 
      }
   ] 
}'

# Insert document without a nested doc
curl -XPOST http://localhost:9200/nested/type/ -d '{}'

# Assert that there are 2 documents
curl http://localhost:9200/nested/type/_count

# Only returns 1 hit, but expected 2
curl -XGET http://localhost:9200/nested/type/_search -d '
{
   "size":0,
   "fields":[],
   "query":{
      "nested":{
         "query":{
            "match_all":{}
         },
         "path":"list"
      }
   }
}'