Searches issues having attachments, additionally you can further refine your query by using a number expression.
A 'number expression' is made of an optional operator representing by its mathematical symbol and a (prositive/negative) number.
Let's see the allowed symbols...
Not equals to
Greater than or equals to
Less than or equals to
By default, this function only includes issues with at least one attachment even if you use the '<' or '<=' operator. You must explicity add 'issues NOT IN hasAttachments()' clause to your query, if you also want to search for issues without attachments.