Can I define default type for text as keyword inside an object type? - elasticsearch

Question

Let's say I have the following mapping:
{
"mappings": {
"_doc": {
"properties": {
"id": {"type": "keyword"},
"params": {
"type": "object",
},
}
}
}
}
params has a lot of fields with numeric and textual values. I don't want to specify all the fields of it but I would like to specify that all the text fields should be of keyword type instead of text which is the default and is analysed (which I want to avoid).
How can I do this? I'm using ElasticSearch 6.7

Answer 1

This is called Dynamic Templates (See https://www.elastic.co/guide/en/elasticsearch/reference/6.7/dynamic-templates.html)
For your question you can define the mapping as follows:
PUT my_index
{
"mappings": {
"_doc": {
"dynamic_templates": [
{
"strings": {
"match_mapping_type": "string",
"mapping": {
"type": "keyword"
}
}
}
]
}
}
}
This transforms all the detected string fields to keyword. If you want to apply only to a subset of fields, you can use match, unmatch, path_match or path_unmatch clauses. (See the docs for differences between them).

Answer 2

Adding to what #banuj mentioned:
It seems that it is possible to combine match_mapping_type and path_match to achieve what I wanted.
PUT my_index
{
"mappings": {
"_doc": {
"dynamic_templates": [
{
"keyword params": {
"mapping": {
"type": "keyword"
},
"match_mapping_type": "string",
"path_match": "params.*"
}
}
]
}
}
}