Elasticsearch查询多种类型并按类型分组？

Question

Suppose I am to search against two types [cars] and [buildings], and I would want the results to be separated. Is there a way one can group results by types?

I understand one simple way will be to query each types separately, but for other use cases one may actually need to query tens or hundreds of types together. Is there a native way or hacky way(like using sort) to achieve this?

Answer 1

This type of grouping behavior is (currently) not available in elasticsearch. It has been a long standing request: https://github.com/elasticsearch/elasticsearch/issues/256

There are two approaches that can help, both of which are far from perfect, but may be good enough for some use cases.

• Client side aggregation. Request a lot more results than you plan on displaying and the then bucket those.
• Using multi-query. This allows you to easily pass down some number of queries in a single batch, but will have potential scaling problems if the number of queries gets to large.

This is one feature that Solr has that elasticsearch doesn't, but I have never tried it. I used a similar feature with Autonomy IDOL years back, but the performance was abysmal.

Answer 2

If you want the results separated in groups of documents, you're going to have to restructure your documents, since, elasticsearch is focused on finding matching documents. You might get around this by designing a document that has child documents then you can query for matches on the parent document that represents your type.

Answer 3

I guess there might be some common field (let's say it's [price]) if you want to search against different types. Then it would be reasonable to add some different type like [price_aggregator] and put into it fields [type] and [price]. And then you could easily build your query against just one type. This requires some additional work while indexing and more memory to store index but it's much performant when you search.