Matching closest ancestor with Path Hierarchy Tokenizer - elasticsearch

Question

I've got an Elasticsearch v5 index set up for mapping config hashes to URLs.
{
"settings": {
"analysis": {
"analyzer": {
"url-analyzer": {
"type": "custom",
"tokenizer": "url-tokenizer"
}
},
"tokenizer": {
"url-tokenizer": {
"type": "path_hierarchy",
"delimiter": "/"
}
}
}
},
"mappings": {
"route": {
"properties": {
"uri": {
"type": "string",
"index": "analyzed",
"analyzer": "url-analyzer"
},
"config": {
"type": "object"
}}}}}
I would like to match the longest path prefix with the highest score, so that given the documents
{ "uri": "/trousers/", "config": { "foo": 1 }}
{ "uri": "/trousers/grey", "config": { "foo": 2 }}
{ "uri": "/trousers/grey/lengthy", "config": { "foo": 3 }}
when I search for /trousers, the top result should be trousers, and when I search for /trousers/grey/short the top result should be /trousers/grey.
Instead, I'm finding that the top result for /trousers is /trousers/grey/lengthy.
How can I index and query my documents to achieve this?

Answer 1

I have one solution, after drinking on it: what if we treat the URI in the index as a keyword, but still use the PathHierarchyTokenizer on the search input?
Now we store the following docs:
/trousers
/trousers/grey
/trousers/grey/lengthy
When we submit a query for /trousers/grey/short, the search_analyzer can build the input [trousers, trousers/grey, trousers/grey/short].
The first two of our documents will match, and we can trivially select the longest match using a custom sort.
Now our mapping document looks like this:
{
"settings": {
"analysis": {
"analyzer": {
"uri-analyzer": {
"type": "custom",
"tokenizer": "keyword"
},
"uri-query": {
"type": "custom",
"tokenizer": "uri-tokenizer"
}
},
"tokenizer": {
"uri-tokenizer": {
"type": "path_hierarchy",
"delimiter": "/"
}
}
}},
"mappings": {
"route": {
"properties": {
"uri": {
"type": "text",
"fielddata": true,
"analyzer": "uri-analyzer",
"search_analyzer": "uri-query"
},
"config": {
"type": "object"
}
}
}
}
}
```
and our query looks like this:
{
"sort": {
"_script": {
"script": "doc.uri.length",
"order": "asc",
"type": "number"
}
},
"query": {
"match": {
"uri": {
"query": "/trousers/grey/lengthy",
"type": "boolean"
}
}
}
}