elastic search copy_to field not filled - elasticsearch

Question

I'm trying to copy a main title field in Elastic Search 5.6, to an other field with: index:false, so I can use this field to match the exact value.
However. After the reindex, and performed search with _source:["exact_hoofdtitel"], the field "exact_hoofdtitel" is not filled with the value of "hoofdtitel".
PUT producten_prd_5_test
{
"aliases": {},
"mappings": {
"boek": {
"properties": {
"hoofdtitel": {
"type": "text",
"copy_to": [
"suggest-hoofdtitel", "exact_hoofdtitel"
]
},
"suggest-hoofdtitel": {
"type": "completion",
"analyzer": "simple",
"preserve_separators": false,
"preserve_position_increments": true,
"max_input_length": 50
},
"exact_hoofdtitel":{
"type":"text",
"fields":{
"keyword":{
"type":"keyword",
"index":false
}
}
},
}
}
},
"settings": {
"number_of_shards": "1",
"number_of_replicas": "0"
}
}
GET producten_prd_5_test/_search
{
"_source":["hoofdtitel","exact_hoofdtitel"]
}
hits": [
{
"_index": "producten_prd_5_test",
"_type": "boek",
"_id": "9781138340671",
"_score": 1,
"_source": {
"hoofdtitel": "The Nature of the Firm in the Oil Industry"
}
},

Answer 1

I believe that you can achieve what you want without copy_to. Let me show you how and why you don't need it here.
How can I make both full-text and exact match queries on the same field?
This can be done with fields mapping attribute. Basically, with the following piece of mapping:
PUT producten_prd_5_test_new
{
"aliases": {},
"mappings": {
"boek": {
"properties": {
"hoofdtitel": {
"type": "text", <== analysing for full text search
"fields": {
"keyword": {
"type": "keyword" <== analysing for exact match
},
"suggest": {
"type": "completion", <== analysing for suggest
"analyzer": "simple",
"preserve_separators": false,
"preserve_position_increments": true,
"max_input_length": 50
}
}
}
}
}
}
}
you will be telling Elasticsearch to index the same field three times: one for full-text search, one for exact match and one for suggest.
The exact search will be possible to do via a term query like this:
GET producten_prd_5_test_new/_search
{
"query": {
"term": {
"hoofdtitel.keyword": "The Nature of the Firm in the Oil Industry"
}
}
}
Why the field exact_hoofdtitel does not appear in the returned document?
Because copy_to does not change the source:
The original _source field will not be modified to show the copied
values.
It works like _all field, allowing you to concat values of multiple fields in one imaginary field and analyse it in a special way.
Does it make sense to do a copy_to to an index: false field?
With index: false the field will not be analyzed and will not be searchable (like in your example, the field exact_hoofdtitel.keyword).
It may still make sense to do so if you want to do keyword aggregations on that field:
GET producten_prd_5_test/_search
{
"aggs": {
"by copy to": {
"terms": {
"field": "exact_hoofdtitel.keyword"
}
}
}
}
This will return something like:
{
"aggregations": {
"by copy to": {
"doc_count_error_upper_bound": 0,
"sum_other_doc_count": 0,
"buckets": [
{
"key": "The Nature of the Firm in the Oil Industry",
"doc_count": 1
}
]
}
}
}