fix: selectedFields on getRows not working correctly

src/bigquery.ts

@@ -376,12 +376,33 @@ export class BigQuery extends common.Service {
    *
    * @param {object} schema
    * @param {array} rows
+   * @param {array} selectedFields List of fields to return.
+   * If unspecified, all fields are returned.
    * @returns {array} Fields using their matching names from the table's schema.
    */
   static mergeSchemaWithRows_(
     schema: TableSchema | TableField,
-    rows: TableRow[]
+    rows: TableRow[],
+    selectedFields?: string[]
   ) {
+    if (selectedFields && selectedFields!.length > 0) {
+      const selectedFieldsArray = selectedFields!.map(c => {
+        return c.split('.');
+      });
+
+      const currentFields = selectedFieldsArray.map(c => c.shift());
+      //filter schema fields based on selected fields.
+      schema.fields = schema.fields?.filter(
+        field =>
+          currentFields
+            .map(c => c!.toLowerCase())
+            .indexOf(field.name!.toLowerCase()) >= 0
+      );
+      selectedFields = selectedFieldsArray
+        .filter(c => c.length > 0)
+        .map(c => c.join('.'));
+    }
+
     return arrify(rows)
       .map(mergeSchema)
       .map(flattenRows);
@@ -391,10 +412,10 @@ export class BigQuery extends common.Service {
         let value = field.v;
         if (schemaField.mode === 'REPEATED') {
           value = (value as TableRowField[]).map(val => {
-            return convert(schemaField, val.v);
+            return convert(schemaField, val.v, selectedFields);
           });
         } else {
-          value = convert(schemaField, value);
+          value = convert(schemaField, value, selectedFields);
         }
         // eslint-disable-next-line @typescript-eslint/no-explicit-any
         const fieldObject: any = {};
@@ -403,8 +424,12 @@ export class BigQuery extends common.Service {
       });
     }
 
-    // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    function convert(schemaField: TableField, value: any) {
+    function convert(
+      schemaField: TableField,
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
+      value: any,
+      selectedFields?: string[]
+    ) {
       if (is.null(value)) {
         return value;
       }
@@ -434,7 +459,11 @@ export class BigQuery extends common.Service {
           break;
         }
         case 'RECORD': {
-          value = BigQuery.mergeSchemaWithRows_(schemaField, value).pop();
+          value = BigQuery.mergeSchemaWithRows_(
+            schemaField,
+            value,
+            selectedFields
+          ).pop();
           break;
         }
         case 'DATE': {

src/table.ts

@@ -1678,7 +1678,11 @@ class Table extends common.ServiceObject {
         callback!(err, null, null, resp);
         return;
       }
-      rows = BigQuery.mergeSchemaWithRows_(this.metadata.schema, rows || []);
+      rows = BigQuery.mergeSchemaWithRows_(
+        this.metadata.schema,
+        rows || [],
+        options.selectedFields ? options.selectedFields!.split(',') : []
+      );
       callback!(null, rows, nextQuery, resp);
     };
 

test/table.ts

@@ -2025,6 +2025,112 @@ describe('BigQuery/Table', () => {
         done();
       });
     });
+
+    it('should return selected fields', done => {
+      const selectedFields = 'age';
+      const rows = [{f: [{v: 40}]}];
+      const schema = {
+        fields: [
+          {name: 'name', type: 'string'},
+          {name: 'age', type: 'INTEGER'},
+        ],
+      };
+      const result = [{age: 40}];
+
+      table.metadata = {schema};
+
+      sandbox.restore();
+
+      table.request = (reqOpts: DecorateRequestOptions, callback: Function) => {
+        callback(null, {rows});
+      };
+
+      table.getRows({selectedFields}, (err: Error, rows: {}) => {
+        assert.ifError(err);
+        assert.deepStrictEqual(rows, result);
+        done();
+      });
+    });
+
+    it('should return selected fields from nested objects', done => {
+      const selectedFields = 'objects.nested_object.nested_property_1';
+      const rows = [
+        {
+          f: [
+            {
+              v: [
+                {
+                  v: {
+                    f: [
+                      {
+                        v: {
+                          f: [
+                            {
+                              v: 'nested_property_1_value',
+                            },
+                          ],
+                        },
+                      },
+                    ],
+                  },
+                },
+              ],
+            },
+          ],
+        },
+      ];
+      const schema = {
+        fields: [
+          {name: 'name', type: 'string'},
+          {
+            name: 'objects',
+            type: 'RECORD',
+            mode: 'REPEATED',
+            fields: [
+              {
+                name: 'nested_object',
+                type: 'RECORD',
+                fields: [
+                  {
+                    name: 'nested_property',
+                    type: 'STRING',
+                  },
+                  {
+                    name: 'nested_property_1',
+                    type: 'STRING',
+                  },
+                ],
+              },
+            ],
+          },
+        ],
+      };
+      const result = [
+        {
+          objects: [
+            {
+              nested_object: {
+                nested_property_1: 'nested_property_1_value',
+              },
+            },
+          ],
+        },
+      ];
+
+      table.metadata = {schema};
+
+      sandbox.restore();
+
+      table.request = (reqOpts: DecorateRequestOptions, callback: Function) => {
+        callback(null, {rows});
+      };
+
+      table.getRows({selectedFields}, (err: Error, rows: {}) => {
+        assert.ifError(err);
+        assert.deepStrictEqual(rows, result);
+        done();
+      });
+    });
   });
 
   describe('insert', () => {