[FTS] Issues when using edge_ngram token_filter

Build : 4.7.0-971

Test : (not yet merged)
./testrunner -i resources/jenkins/fts.ini -t fts.stable_topology_fts.StableTopFTS.index_query_custom_mapping,items=1000,custom_map=True,num_custom_analyzers=1,multiple_filters=true,cm_id=0,num_queries=100,compare_es=True,GROUP=P0,cluster=D+F

Description : For the above test, there are 3 queries that return different hits in case of FTS vs ES in case the custom analyzer uses an edge_ngram token filter with back=true,min=3 and max=5 params. There are two cases here –

1) 2 queries using match_phrase. It seems that FTS does not correctly use edge_ngram with match_phrase type of queries. This looks like a bug to me in FTS.
2) 1 query which has should, must_not and must Boolean queries. I think FTS is correct here in not hitting a few documents.

Case 1 : Match Phrase with back_edge_ngram (min 3, max 5)

Query :

Doc not returned by FTS, but returned by ES :

{

  "salary": 60402.95,

  "name": "Antonia Gerónimo",

  "dept": "Info-tech",

  "is_manager": false,

  "mutated": 0,

  "join_date": "1971-02-11T06:57:00",

  "languages_known": [

    "Hindi",

    "Italian",

    "Spanish"

  ],

  "emp_id": "10000318",

  "type": "emp",

  "email": "antonia@mcdiabetes.com"

}

Case 2: Use of should, must_not and must Boolean queries.

Query :
{
"should":{"disjuncts": [

,

]},
"must_not": {"disjuncts": [

,

]},
"must": {"conjuncts": [

]}
}

Sample doc not returned by FTS, but returned by ES :

{

  "salary": 91984.77,

  "name": "Keelia Carter",

  "mutated": 0,

  "is_manager": true,

  "dept": "Support",

  "join_date": "1952-01-24T10:20:00",

  "manages": {

    "team_size": 6,

    "reports": [

      "Ciara Ann",

      "Kala Moore",

      "Severin Hall",

      "Deandra Aarón",

      "Mia Parker X",

      "Hedda Jr."

    ]

  },

  "languages_known": [

    "Arabic",

    "Vietnamese",

    "Portuguese"

  ],

  "emp_id": "10000120",

  "type": "emp",

  "email": "keelia@mcdiabetes.com"

}

Attaching the testrunner console output which has the index definition as well the query results.