If you are using the default analyzer (standard
) there is nothing for it to analyze if it is an empty string. So you need to index the field verbatim (not analyzed). Here is an example:
Add a mapping that will index the field untokenized, if you need a tokenized copy of the field indexed as well you can use a Multi Field type.
PUT http://localhost:9200/test/_mapping/demo
{
"demo": {
"properties": {
"_content": {
"type": "string",
"index": "not_analyzed"
}
}
}
}
Next, index a couple of documents.
/POST http://localhost:9200/test/demo/1/
{
"_content": ""
}
/POST http://localhost:9200/test/demo/2
{
"_content": "some content"
}
Execute a search:
POST http://localhost:9200/test/demo/_search
{
"query": {
"filtered": {
"filter": {
"term": {
"_content": ""
}
}
}
}
}
Returns the document with the empty string.
{
took: 2,
timed_out: false,
_shards: {
total: 5,
successful: 5,
failed: 0
},
hits: {
total: 1,
max_score: 0.30685282,
hits: [
{
_index: test,
_type: demo,
_id: 1,
_score: 0.30685282,
_source: {
_content: ""
}
}
]
}
}