# Best way to count Child object matches? **URL:** \ **Category:** Elasticsearch\ **Created:** [November 13, 2012, 11:29pm UTC](https://discuss.elastic.co/t/best-way-to-count-child-object-matches/9706 "2012-11-13T23:29:47Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![phill](https://avatars.discourse-cdn.com/v4/letter/p/779978/32.png) [@phill](https://discuss.elastic.co/u/phill)\ **Post date:** [November 13, 2012, 11:29pm UTC](https://discuss.elastic.co/t/best-way-to-count-child-object-matches/9706/1 "2012-11-13T23:29:47Z")
If I have a parent and child relationship I can write a query to find all parents that match criteria within the parent and other criteria within the child. I can use a has-child query to see if there are any appropriately matching parents that have matching children The desired scoring is based on relevancy. All is well as long as none of the relevancy scoring is based any fields in the child which in my case is true. Such a query that also includes a has\_child would work great until the application wants to see the count of children. The query hits doesn't give the count of children matched. Count of matching children Approach 1: has\_child, then facet One way that comes to mind to find the count of matching children per parent is to do a termS facet on the scope of the matching children where the term is the "\_parentId" and the stats are for any numeric field in the child. Thus the count statistic from the facet is the count of matching children for a particular parent. The advantage to approach 1, is that the search hits for the query are exactly the results, so "From" and "size" and total hits all are just what is needed. The disadvantage to this approach is that the facet list returned might be huge (the facet would include all matching document IDs and some stats about them). In my case that might be 10ks of facet values. That doesn't sound good at all. Approach 2: has\_parent Invert the whole question. Start looking for the children that match, but also ask about has\_parent that match. That sounds good (or at least it did to me) until I realized that my ranking is based on a score of fields in the parent, so I couldn't actually rank my hits as I wanted. It also suffers from being a list of all children and what is wanted is a list of parents, so requires post processing everything after the fact. Approach 3: 2nd Query After getting the result set of parents, go back to the index just to retrieve all matching children, but only for the page of parents that we are trying to return to the application, it certainly ought to be a quick query being limited by a list of IDs. Then we can report the count of how many children for each parent ID. This does have the advantage that if the application needs something else from the children, we could take the opportunity at that point to get it. Does anyone have any comments or suggests on any of these approaches? -Paul -- ---
**Author:** ![lolcat](https://avatars.discourse-cdn.com/v4/letter/l/7993a0/32.png) [@lolcat](https://discuss.elastic.co/u/lolcat)\ **Post date:** [March 3, 2014, 4:03pm UTC](https://discuss.elastic.co/t/best-way-to-count-child-object-matches/9706/2 "2014-03-03T16:03:23Z")
Hi, Did you manage to come up with an appropriate solution to manage counting child documents when you want a count of matches when performing the has\_child query ? Thanks for your time 🙂 ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 6, 2017, 1:46am UTC](https://discuss.elastic.co/t/best-way-to-count-child-object-matches/9706/3 "2017-07-06T01:46:10Z")