How do boolean predicates work in Elasticsearch query string syntax

Elastic Stack Elasticsearch
1

I have a question regarding the ES query string syntax 8Version 1.5.0). I am searching
logstash log-entries containg xml documents and I'd like to search for
documents containg certain XML attributes with certain values. When
my query string looks like this:

id: foo AND attrName="SomeValue" AND field2:bar

I get all documents where:

  • id=foo
    AND
  • field2=bar
    AND
  • contain the text attrName AND the text SomeValue

When I change my query to (added parentheses):

id: foo AND (attrName="SomeValue") AND field2:bar

I get all documents where:

  • id=foo
    AND
  • field2=bar
    AND
  • contain the text attrName OR the text SomeValue

Why is (attrName="SomeValue") evaluated as attrName OR SomeValue, whereas without parentheses it is attrName AND SomeValue?

My search JSON is:

{
"sort": [
"@timestamp"
],
"query": {
"query_string": {
"query": "mySearchText"
}
},
"fields": [
"_id"
],
"size": 100
}