Queries with aliased where predicate > and < , use primary scans instead of expected index scan

1. load 13M data on sabre-default bucket
2. create indexes on default - all successful

3. Most of the expected queries were taking longer to run, so I ran the explain stmts to check - looks like each query was using the primary scan inplace of expected Index scan.
cbq> select * from system:indexes where keyspace_id="default";
{
"requestID": "85f1adb5-4b8d-489a-a4a3-4cbe4b61aa6b",
"signature":

{ "*": "*" }

,
"results": [
{
"indexes":

{ "datastore_id": "http://127.0.0.1:8091", "id": "cc9643d53917d052", "index_key": [ "`SequenceNumber`" ], "keyspace_id": "default", "name": "seq_num", "namespace_id": "default", "state": "online", "using": "gsi" }

},
{
"indexes":

{ "datastore_id": "http://127.0.0.1:8091", "id": "ba277bd5832cc61", "index_key": [], "is_primary": true, "keyspace_id": "default", "name": "px_default", "namespace_id": "default", "state": "online", "using": "gsi" }

},
{
"indexes":

{ "datastore_id": "http://127.0.0.1:8091", "id": "fb6582da11ef61ca", "index_key": [ "((`AirItinerary`.`OriginDestinationOptions`).`OriginDestinationOption`)" ], "keyspace_id": "default", "name": "airportcode", "namespace_id": "default", "state": "pending", "using": "gsi" }

},
{
"indexes":

{ "datastore_id": "http://127.0.0.1:8091", "id": "f2e31e0f3021497e", "index_key": [ "(((((`AirItineraryPricingInfo`.`PTC_FareBreakdowns`).`PTC_FareBreakdown`).`PassengerFare`).`TotalFare`).`Amount`)" ], "keyspace_id": "default", "name": "amt", "namespace_id": "default", "state": "online", "using": "gsi" }

}
],
"status": "success",
"metrics":

{ "elapsedTime": "1.555576513s", "executionTime": "1.555072793s", "resultCount": 4, "resultSize": 1831 }

}

cbq> explain select AirItineraryPricingInfo.PTC_FareBreakdowns.PTC_FareBreakdown.PassengerFare.TotalFare.Amount as a123 from default where a123}
{
"requestID": "e28feb99-47d0-4c57-a0bf-ea698d44cbec",
"signature": "json",
"results": [
{
"#operator": "Sequence",
"~children": [
{
"#operator": "Sequence",
"~children": [

{ "#operator": "PrimaryScan", "index": "px_default", "keyspace": "default", "namespace": "default", "using": "gsi" }

,
{
"#operator": "Parallel",
"~child": {
"#operator": "Sequence",
"~children": [

{ "#operator": "Fetch", "keyspace": "default", "namespace": "default" }

,

{ "#operator": "Filter", "condition": "((250 \u003c (`default`.`a123`)) and ((`default`.`a123`) \u003c 450))" }

,
{
"#operator": "InitialProject",
"result_terms": [

{ "as": "a123", "expr": "((((((`default`.`AirItineraryPricingInfo`).`PTC_FareBreakdowns`).`PTC_FareBreakdown`).`PassengerFare`).`TotalFare`).`Amount`)" }

]
},

{ "#operator": "FinalProject" }

]
}
}
]
},

{ "#operator": "Limit", "expr": "2" }

]
}
],
"status": "success",
"metrics":

{ "elapsedTime": "2.312823047s", "executionTime": "2.197771563s", "resultCount": 1, "resultSize": 2217 }

}

4. The above uses indexscan when I use full field reference instead of the alias
cbq>

{.PTC_FareBreakdowns.PTC_FareBreakdown.PassengerFare.TotalFare.Amount>250 and AirItineraryPricingInfo.PTC_FareBreakdowns.PTC_FareBreakdown}

{
"requestID": "5483c80b-f471-4616-808b-c1a86cd46554",
"signature": "json",
"results": [
{
"#operator": "Sequence",
"~children": [
{
"#operator": "Sequence",
"~children": [
{
"#operator": "IndexScan",
"index": "amt",
"keyspace": "default",
"limit": 9.223372036854776e+18,
"namespace": "default",
"spans": [
{
"Range":

{ "High": [ "450" ], "Inclusion": 0, "Low": [ "250" ] }

,
"Seek": null
}
],
"using": "gsi"
},
{
"#operator": "Parallel",
"~child": {
"#operator": "Sequence",
"~children": [

{ "#operator": "Fetch", "keyspace": "default", "namespace": "default" }

,

{ "#operator": "Filter", "condition": "((250 \u003c ((((((`default`.`AirItineraryPricingInfo`).`PTC_FareBreakdowns`).`PTC_FareBreakdown`).`PassengerFare`).`TotalFare`).`Amount`)) and (((((((`default`.`AirItineraryPricingInfo`).`PTC_FareBreakdowns`).`PTC_FareBreakdown`).`PassengerFare`).`TotalFare`).`Amount`) \u003c 450))" }

,
{
"#operator": "InitialProject",
"result_terms": [

{ "as": "a123", "expr": "((((((`default`.`AirItineraryPricingInfo`).`PTC_FareBreakdowns`).`PTC_FareBreakdown`).`PassengerFare`).`TotalFare`).`Amount`)" }

]
},

{ "#operator": "FinalProject" }

]
}
}
]
},

{ "#operator": "Limit", "expr": "2" }

]
}
],
"status": "success",
"metrics":

{ "elapsedTime": "7.540619ms", "executionTime": "7.310345ms", "resultCount": 1, "resultSize": 3095 }

}