SearchAPI - OR query returns all documents

[scragraham]

Summary
When running a query with the OR operator, the search results return all documents instead of the two expected.

Steps to Reproduce
Input documents:

      json={"index": "index-1", "documents": [
        { 
          "id": "a",
          "text1": "hello world",
          "text2": "testing search api and world"
        },
        { 
          "id": "b",
          "anotherText": "There is also a corresponding asynchronous method, "
        },
        { 
          "id": "c",
          "text3": "This string also contains the word world and api"
        },
        { 
          "id": "firstdate",
          "date_entered": "2018-12-12",
          "text4": "This is a test of the national broadcasting system"
        },
        { 
          "id": "seconddate",
          "date_entered": "2019-04-04",
          "text5": "Who are the britons?"
        }
      ]}

Unittest:

  def test_search_query_OR(self):
    response = self.app.post(
      '/python/search/search',
      json={"index": "index-1", "query": "hello OR britons"})

    self.assertEquals(response.status_code, 200)
    self.assertIn('documents', response.json())
    documents = response.json()['documents']
    self.assertEquals(len(documents), 2)

Expected Results
2 documents: id: a, id: seconddate

Actual Results
all 5 documents.

Debug Logging from /var/log/appscale/search.log

2018-12-14 22:22:23,085 DEBUG solr_interface.py:333 Solr results: {'responseHeader': {'status': 0, 'QTime': 2, 'params': {'defType': 'edismax', 'rows': '20', 'q': '_gaeindex_name:hawkeyepython27__index-1 AND  AND (%22hello%22 OR%22britons%22)', 'start': '0', 'wt': 'json', 'pf': 'hawkeyepython27__index-1_anotherText hawkeyepython27__index-1_date_entered hawkeyepython27__index-1_text1 hawkeyepython27__index-1_text2 hawkeyepython27__index-1_text3 hawkeyepython27__index-1_text4 hawkeyepython27__index-1_text5', 'qf': 'hawkeyepython27__index-1_anotherText hawkeyepython27__index-1_date_entered hawkeyepython27__index-1_text1 hawkeyepython27__index-1_text2 hawkeyepython27__index-1_text3 hawkeyepython27__index-1_text4 hawkeyepython27__index-1_text5', 'fl': 'id _gaeindex_locale hawkeyepython27__index-1_anotherText hawkeyepython27__index-1_date_entered hawkeyepython27__index-1_text1 hawkeyepython27__index-1_text2 hawkeyepython27__index-1_text3 hawkeyepython27__index-1_text4 hawkeyepython27__index-1_text5'}}, 'response': {'start': 0, 'numFound': 5, 'docs': [{'_gaeindex_locale': ['en'], 'id': 'a', 'hawkeyepython27__index-1_text1': 'hello world', 'hawkeyepython27__index-1_text2': 'testing search api and world'}, {'_gaeindex_locale': ['en'], 'id': 'b', 'hawkeyepython27__index-1_anotherText': 'There is also a corresponding asynchronous method, '}, {'_gaeindex_locale': ['en'], 'hawkeyepython27__index-1_text3': 'This string also contains the word world and api', 'id': 'c'}, {'_gaeindex_locale': ['en'], 'hawkeyepython27__index-1_text4': 'This is a test of the national broadcasting system', 'id': 'firstdate', 'hawkeyepython27__index-1_date_entered': '2018-12-12'}, {'_gaeindex_locale': ['en'], 'hawkeyepython27__index-1_text5': 'Who are the britons?', 'id': 'seconddate', 'hawkeyepython27__index-1_date_entered': '2019-04-04'}]}}

Pretty printed:

{
    "response": {
        "docs": [
            {
                "_gaeindex_locale": [
                    "en"
                ],
                "hawkeyepython27__index-1_text1": "hello world",
                "hawkeyepython27__index-1_text2": "testing search api and world",
                "id": "a"
            },
            {
                "_gaeindex_locale": [
                    "en"
                ],
                "hawkeyepython27__index-1_anotherText": "There is also a corresponding asynchronous method, ",
                "id": "b"
            },
            {
                "_gaeindex_locale": [
                    "en"
                ],
                "hawkeyepython27__index-1_text3": "This string also contains the word world and api",
                "id": "c"
            },
            {
                "_gaeindex_locale": [
                    "en"
                ],
                "hawkeyepython27__index-1_date_entered": "2018-12-12",
                "hawkeyepython27__index-1_text4": "This is a test of the national broadcasting system",
                "id": "firstdate"
            },
            {
                "_gaeindex_locale": [
                    "en"
                ],
                "hawkeyepython27__index-1_date_entered": "2019-04-04",
                "hawkeyepython27__index-1_text5": "Who are the britons?",
                "id": "seconddate"
            }
        ],
        "numFound": 5,
        "start": 0
    },
    "responseHeader": {
        "QTime": 2,
        "params": {
            "defType": "edismax",
            "fl": "id _gaeindex_locale hawkeyepython27__index-1_anotherText hawkeyepython27__index-1_date_entered hawkeyepython27__index-1_text1 hawkeyepython27__index-1_text2 hawkeyepython27__index-1_text3 hawkeyepython27__index-1_text4 hawkeyepython27__index-1_text5",
            "pf": "hawkeyepython27__index-1_anotherText hawkeyepython27__index-1_date_entered hawkeyepython27__index-1_text1 hawkeyepython27__index-1_text2 hawkeyepython27__index-1_text3 hawkeyepython27__index-1_text4 hawkeyepython27__index-1_text5",
            "q": "_gaeindex_name:hawkeyepython27__index-1 AND  AND (%22hello%22 OR%22britons%22)",
            "qf": "hawkeyepython27__index-1_anotherText hawkeyepython27__index-1_date_entered hawkeyepython27__index-1_text1 hawkeyepython27__index-1_text2 hawkeyepython27__index-1_text3 hawkeyepython27__index-1_text4 hawkeyepython27__index-1_text5",
            "rows": "20",
            "start": "0",
            "wt": "json"
        },
        "status": 0
    }
}

The query to solr seems a bit off:

"q": "_gaeindex_name:hawkeyepython27__index-1 AND  AND (%22hello%22 OR%22britons%22)",