Here you can find some most popular search examples. Just copy and paste with some modifications into the textarea: 

Find by Comment Author

This query will find all issues where a user with some@email.com email has left a comment

{
  "fields.comment.comments.author.emailAddress": "some@email.com"
}

Find by Linked Issues

This query will find all issues which have incoming or outgoing link "Block"

{
  "fields.issuelinks.type.name": "Block"
}

The query below finds all issues that are linked as "Blocks", are neither "Closed" nor "Resolved" and which are being linked by issues from the "MORPH" project

{
  "fields.issuelinks": {
    "$elemMatch": {
      "type.name": "Blocks",
      "inwardIssue.key": {"$regex": "MORPH-"},
      "inwardIssue.fields.status.name": {
        "$nin": [
          "Closed",
          "Resolved"
        ]
      }
    }
  }
}

Find not Finished Subtasks in a Sprint

All open subtasks within a sprint can be found using the following query:

{
  "fields.customfield_10007": {"$regex": "Sample Sprint 2"},
  "fields.issuetype.subtask": true,
  "fields.status.name": {"$nin": ["Done"]}
}

where fields.customfield_10007 is the Sprint Name Custom Field, and "Sample Sprint 2" is the actual Sprint name

Find Tasks that has not Finished Subtasks in a Sprint

 Similar to the query above, but slightly reversed:

{
  "fields.customfield_10007": {"$regex": "Sample Sprint 2"},
  "fields.issuetype.subtask": false,
  "fields.subtasks.fields.status.name": {"$nin": ["Done"]}
}

Reusing Results from Previous Search Query

It is also possible to use array of search queries, passing the "__RESULT__" keyword (which contains issues keys from the previous query) into the second query.

[{...}, {...}]

For example, the query below would read like this (from second to first):

Find Tasks with link type "Blocks" and which are not blocking Stories where some@gmail.com has left a comment

[{
  "fields.issuetype.name": "Story",
  "fields.comment.comments.author.emailAddress": "some@gmail.com"
},
{
  "fields.issuelinks.outwardIssue.fields.issuetype.name": "Task",
  "fields.issuelinks.type.name": "Blocks",
  "fields.issuelinks.outwardIssue.key": {"$nin": "__RESULT__"}
}]

All keys from the first query will be passed instead of the __RESULT__ into the second query.