feat(bigquery): expose query id on row iterator if available

bigquery/iterator.go

@@ -91,6 +91,14 @@
 	}
 }
 
+// QueryId returns a query ID if available, or an empty string.
+func (ri *RowIterator) QueryId() string {
+	if ri.src == nil {
+		return ""
+	}
+	return ri.src.queryId
+}
+
 // We declare a function signature for fetching results.  The primary reason
 // for this is to enable us to swap out the fetch function with alternate
 // implementations (e.g. to enable testing).
@@ -210,8 +218,9 @@
 //     want to retain the data unnecessarily, and we expect that the backend
 //     can always provide them if needed.
 type rowSource struct {
-	j *Job
-	t *Table
+	j       *Job
+	t       *Table
+	queryId string
 
 	cachedRows      []*bq.TableRow
 	cachedSchema    *bq.TableSchema

bigquery/iterator_test.go

@@ -510,3 +510,36 @@ func TestIteratorSourceJob(t *testing.T) {
 		}
 	}
 }
+
+func TestIteratorQueryId(t *testing.T) {
+	testcases := []struct {
+		description string
+		src         *rowSource
+		want        string
+	}{
+		{
+			description: "nil source",
+			src:         nil,
+			want:        "",
+		},
+		{
+			description: "empty source",
+			src:         &rowSource{},
+			want:        "",
+		},
+		{
+			description: "populated id",
+			src:         &rowSource{queryId: "foo"},
+			want:        "foo",
+		},
+	}
+
+	for _, tc := range testcases {
+		// Don't pass a page func, we're not reading from the iterator.
+		it := newRowIterator(context.Background(), tc.src, nil)
+		got := it.QueryId()
+		if got != tc.want {
+			t.Errorf("%s: mismatch queryid, got %q want %q", tc.description, got, tc.want)
+		}
+	}
+}

bigquery/query.go

@@ -412,7 +412,8 @@ func (q *Query) Read(ctx context.Context) (it *RowIterator, err error) {
 			}
 		}
 		rowSource := &rowSource{
-			j: minimalJob,
+			j:       minimalJob,
+			queryId: resp.QueryId,
 			// RowIterator can precache results from the iterator to save a lookup.
 			cachedRows:      resp.Rows,
 			cachedSchema:    resp.Schema,