Log cql query on error (#1250)

Signed-off-by: Prithvi Raj <p.r@uber.com>

Author: vprithvi

plugin/storage/cassandra/spanstore/reader.go

@@ -410,7 +410,8 @@ func (s *SpanReader) executeQuery(span opentracing.Span, query cassandra.Query,
 	tableMetrics.Emit(err, time.Since(start))
 	if err != nil {
 		logErrorToSpan(span, err)
-		s.logger.Error("Failed to exec query", zap.Error(err))
+		span.LogFields(otlog.String("query", query.String()))
+		s.logger.Error("Failed to exec query", zap.Error(err), zap.String("query", query.String()))
 		return nil, err
 	}
 	return retMe, nil

plugin/storage/cassandra/spanstore/reader_test.go

@@ -305,6 +305,7 @@ func TestSpanReaderFindTraces(t *testing.T) {
 					query.On("Consistency", cassandra.One).Return(query)
 					query.On("PageSize", 0).Return(query)
 					query.On("Iter").Return(iter)
+					query.On("String").Return("queryString")
 
 					return query
 				}