aggregation on path hierarchy tokens

I found a couple of great articles on this issue (here and here), and also experimented a bit. While the two articles reference an older version, a few tweaks got things working with ES 6.

Here's what worked for me, I haven't tested with multiple categories per item (e.g. your array example), but it would likely still work:

{  "settings": {    "analysis": {      "analyzer": {        "path-analyzer": {          "tokenizer": "path-tokenizer"        }      },      "tokenizer": {        "path-tokenizer": {          "type": "path_hierarchy",          "delimiter": "|"        }      }    }  },  "mappings": {    "item": {      "dynamic": "strict",      "properties": {        "category_path": {          "type": "text",          "analyzer": "path-analyzer",          "search_analyzer": "keyword",          "fielddata": true        }      }    }  }}

Your aggregations request would look something like this:

{  "aggs": {    "category": {      "terms": {        "field": "category_path"      }    }  },  "size": 0}

And your results:

  "buckets": [    {      "key": "Men",      "doc_count": 11    },    {      "key": "Men|Sale",      "doc_count": 4    },    {      "key": "Men|Tops",      "doc_count": 3    },    {      "key": "Men|Tops|Shirts",      "doc_count": 2    }  ]