# Difference of Sets in ES
**URL:** https://discuss.elastic.co/t/difference-of-sets-in-es/362924
**Category:** Elasticsearch
**Created:** [July 11, 2024, 2:13am UTC](https://discuss.elastic.co/t/difference-of-sets-in-es/362924 "2024-07-11T02:13:34Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Jader\_Gonzalez](https://discuss.elastic.co/u/Jader_Gonzalez)
#### Post date: [July 11, 2024, 2:13am UTC](https://discuss.elastic.co/t/difference-of-sets-in-es/362924/1 "2024-07-11T02:13:34Z")
I have experience working with SQL and am familiar with performing set differences using SQL. Although I understand that Elasticsearch (ES) operates differently, I believe there must be an efficient method for achieving a set difference of two indices in ES. To clarify my question, let's consider the scenario where index A contains all elements within a certain universe, and index B consists of only specific elements from A. Essentially, every element x in B also exists in A.
Given this, I am seeking a way to calculate the difference between A and B, meaning identifying elements in A that do not exist in B. Despite my efforts to find a solution, it seems challenging to achieve this in ES. This is concerning as excluding elements is a common operation in my use case, where A contains millions of records while B is a much smaller subset of A. It is crucial for me to accurately count the number of excluded elements in my logic. Appreciate any kind of help that might be provided.
---
### Author:  [@Justin\_Castilla](https://discuss.elastic.co/u/Justin_Castilla)
#### Post date: [July 11, 2024, 6:51pm UTC](https://discuss.elastic.co/t/difference-of-sets-in-es/362924/2 "2024-07-11T18:51:51Z")
Hello Jader\_Gonzalez! Welcome to the forum!
Just off the top of my head without any real testing or validation, would you be able to add a boolean to an element in index A when it also exists in index B? I'm thinking you could filter for elements in index A where the boolean field you create does NOT exist.
Here's an example I found in a previous post that might illustrate what I'm thinking:
```auto
DELETE test
PUT test/_doc/1
{
"key1" : "value1",
"exists_in_B": true
}
PUT test/_doc/2?refresh
{
"key2" : "value2"
}
GET test/_search
{
"query": {
"bool": {
"must_not": [
{ "exists": { "field": "exists_in_B"}}
]
}
}
}
```
This would be assuming both are made at the same time or this boolean field can be added and updated in a timely and efficient manner. While Set notation isn't a native feature to Elasticsearch, it would be a good addition for some use cases. Hopefully this method helps? Would love to help out more if this isn't something you'd be able to do in your case.