GOCBC-631: Add Metrics to QueryOptions

Motivation
----------
We now disable metrics by default so we need an option to
enable them.

Changes
-------
Add Metrics to QueryOptions. Make Metrics optional on the
metadata for query result.
Change-Id: I0c3cff36d3c254763122a5258b5009726064b4a9
Reviewed-on: http://review.couchbase.org/115659
Reviewed-by: Mike Goldsmith <goldsmith.mike@gmail.com>
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Charles Dixon <chvckd@gmail.com>

cluster_query.go

@@ -59,7 +59,7 @@ type QueryMetrics struct {
 type QueryMetadata struct {
 	requestID       string
 	clientContextID string
-	metrics         QueryMetrics
+	metrics         *QueryMetrics
 	signature       interface{}
 	warnings        []QueryWarning
 	sourceAddr      string
@@ -186,7 +186,7 @@ func (r *QueryMetadata) ClientContextID() string {
 }
 
 // Metrics returns metrics about execution of this result.
-func (r *QueryMetadata) Metrics() QueryMetrics {
+func (r *QueryMetadata) Metrics() *QueryMetrics {
 	return r.metrics
 }
 
@@ -233,7 +233,7 @@ func (r *QueryResult) readAttribute(decoder *json.Decoder, t json.Token) (bool,
 			logDebugf("Failed to parse execution time duration (%s)", err)
 		}
 
-		r.metadata.metrics = QueryMetrics{
+		r.metadata.metrics = &QueryMetrics{
 			ElapsedTime:   elapsedTime,
 			ExecutionTime: executionTime,
 			ResultCount:   metrics.ResultCount,

cluster_query_test.go

@@ -393,6 +393,7 @@ func TestBasicQuery(t *testing.T) {
 
 	queryOptions := &QueryOptions{
 		PositionalParameters: []interface{}{"brewery"},
+		Metrics:              true,
 	}
 
 	statement := "select `beer-sample`.* from `beer-sample` WHERE `type` = ? ORDER BY brewery_id, name"

queryoptions.go

@@ -51,6 +51,8 @@ type QueryOptions struct {
 	NamedParameters      map[string]interface{}
 	// Custom allows specifying custom query options.
 	Custom map[string]interface{}
+	// Metrics specifies whether or not to fetch metrics when executing the query.
+	Metrics bool
 
 	// JSONSerializer is used to deserialize each row in the result. This should be a JSON deserializer as results are JSON.
 	// NOTE: if not set then query will always default to DefaultJSONSerializer.
@@ -128,6 +130,10 @@ func (opts *QueryOptions) toMap(statement string) (map[string]interface{}, error
 		}
 	}
 
+	if !opts.Metrics {
+		execOpts["metrics"] = false
+	}
+
 	if opts.ClientContextID == "" {
 		execOpts["client_context_id"] = uuid.New()
 	} else {