SQL Datasources: Fix variable throwing error if query returns no data (#65937)

* Fix SQL query variable throwing error if query returns no data

* Tests to verify that metricFindQuery returns properly and doesn't throw error

* Fix all codepaths that might throw errors because of undefined backendSrv response

public/app/features/plugins/sql/datasource/SqlDatasource.ts

@@ -164,7 +164,7 @@ export abstract class SqlDatasource extends DataSourceWithBackend<SQLQuery, SQLO
         .pipe(
           map((res: FetchResponse<BackendDataSourceResponse>) => {
             const rsp = toDataQueryResponse(res, queries);
-            return rsp.data[0];
+            return rsp.data[0] ?? { fields: [] };
           })
         )
     );

public/app/plugins/datasource/mssql/datasource.test.ts

@@ -5,6 +5,7 @@ import {
   dataFrameToJSON,
   DataSourceInstanceSettings,
   dateTime,
+  FieldType,
   MetricFindValue,
   MutableDataFrame,
   TimeRange,
@@ -80,6 +81,133 @@ describe('MSSQLDatasource', () => {
     });
   });
 
+  describe('When runSql returns an empty dataframe', () => {
+    const response = {
+      results: {
+        tempvar: {
+          refId: 'tempvar',
+          frames: [],
+        },
+      },
+    };
+
+    beforeEach(async () => {
+      fetchMock.mockImplementation(() => of(createFetchResponse(response)));
+    });
+
+    it('should return an empty array when metricFindQuery is called', async () => {
+      const query = 'select * from atable';
+      const results = await ctx.ds.metricFindQuery(query);
+      expect(results.length).toBe(0);
+    });
+
+    it('should return an empty array when fetchDatasets is called', async () => {
+      const results = await ctx.ds.fetchDatasets();
+      expect(results.length).toBe(0);
+    });
+
+    it('should return an empty array when fetchTables is called', async () => {
+      const results = await ctx.ds.fetchTables();
+      expect(results.length).toBe(0);
+    });
+
+    it('should return an empty array when fetchFields is called', async () => {
+      const query: SQLQuery = {
+        refId: 'refId',
+        table: 'schema.table',
+        dataset: 'dataset',
+      };
+      const results = await ctx.ds.fetchFields(query);
+      expect(results.length).toBe(0);
+    });
+  });
+
+  describe('When runSql returns a populated dataframe', () => {
+    it('should return a list of datasets when fetchDatasets is called', async () => {
+      const fetchDatasetsResponse = {
+        results: {
+          datasets: {
+            refId: 'datasets',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [{ name: 'name', type: FieldType.string, values: ['test1', 'test2', 'test3'] }],
+                })
+              ),
+            ],
+          },
+        },
+      };
+      fetchMock.mockImplementation(() => of(createFetchResponse(fetchDatasetsResponse)));
+
+      const results = await ctx.ds.fetchDatasets();
+      expect(results.length).toBe(3);
+      expect(results).toEqual(['test1', 'test2', 'test3']);
+    });
+
+    it('should return a list of tables when fetchTables is called', async () => {
+      const fetchTableResponse = {
+        results: {
+          tables: {
+            refId: 'tables',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [{ name: 'schemaAndName', type: FieldType.string, values: ['test1', 'test2', 'test3'] }],
+                })
+              ),
+            ],
+          },
+        },
+      };
+
+      fetchMock.mockImplementation(() => of(createFetchResponse(fetchTableResponse)));
+
+      const results = await ctx.ds.fetchTables();
+      expect(results.length).toBe(3);
+      expect(results).toEqual(['test1', 'test2', 'test3']);
+    });
+
+    it('should return a list of fields when fetchFields is called', async () => {
+      const fetchFieldsResponse = {
+        results: {
+          columns: {
+            refId: 'columns',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [
+                    { name: 'column', type: FieldType.string, values: ['test1', 'test2', 'test3'] },
+                    { name: 'type', type: FieldType.string, values: ['int', 'char', 'bool'] },
+                  ],
+                })
+              ),
+            ],
+          },
+        },
+      };
+
+      fetchMock.mockImplementation(() => of(createFetchResponse(fetchFieldsResponse)));
+
+      const sqlQuery: SQLQuery = {
+        refId: 'fields',
+        table: 'table',
+        dataset: 'dataset',
+      };
+      const results = await ctx.ds.fetchFields(sqlQuery);
+      expect(results.length).toBe(3);
+      expect(results[0].label).toBe('test1');
+      expect(results[0].value).toBe('test1');
+      expect(results[0].type).toBe('int');
+      expect(results[1].label).toBe('test2');
+      expect(results[1].value).toBe('test2');
+      expect(results[1].type).toBe('char');
+      expect(results[2].label).toBe('test3');
+      expect(results[2].value).toBe('test3');
+      expect(results[2].type).toBe('bool');
+    });
+  });
+
   describe('When performing metricFindQuery with key, value columns', () => {
     let results: MetricFindValue[];
     const query = 'select * from atable';

public/app/plugins/datasource/mssql/datasource.ts

@@ -23,13 +23,13 @@ export class MssqlDatasource extends SqlDatasource {
 
   async fetchDatasets(): Promise<string[]> {
     const datasets = await this.runSql<{ name: string[] }>(showDatabases(), { refId: 'datasets' });
-    return datasets.fields.name.values.toArray().flat();
+    return datasets.fields.name?.values.toArray().flat() ?? [];
   }
 
   async fetchTables(dataset?: string): Promise<string[]> {
     // We get back the table name with the schema as well. like dbo.table
     const tables = await this.runSql<{ schemaAndName: string[] }>(getSchemaAndName(dataset), { refId: 'tables' });
-    return tables.fields.schemaAndName.values.toArray().flat();
+    return tables.fields.schemaAndName?.values.toArray().flat() ?? [];
   }
 
   async fetchFields(query: SQLQuery): Promise<SQLSelectableValue[]> {

public/app/plugins/datasource/mysql/specs/datasource.test.ts

@@ -5,6 +5,7 @@ import {
   DataQueryRequest,
   DataSourceInstanceSettings,
   dateTime,
+  FieldType,
   MutableDataFrame,
 } from '@grafana/data';
 import { FetchResponse, setBackendSrv } from '@grafana/runtime';
@@ -17,7 +18,7 @@ import { MySqlDatasource } from '../MySqlDatasource';
 import { MySQLOptions } from '../types';
 
 describe('MySQLDatasource', () => {
-  const setupTextContext = (response: unknown) => {
+  const setupTestContext = (response: unknown) => {
     jest.clearAllMocks();
     setBackendSrv(backendSrv);
     const fetchMock = jest.spyOn(backendSrv, 'fetch');
@@ -55,7 +56,7 @@ describe('MySQLDatasource', () => {
         ],
       } as unknown as DataQueryRequest<SQLQuery>;
 
-      const { ds, fetchMock } = setupTextContext({});
+      const { ds, fetchMock } = setupTestContext({});
 
       await expect(ds.query(options)).toEmitValuesWith((received) => {
         expect(received[0]).toEqual({ data: [] });
@@ -64,6 +65,132 @@ describe('MySQLDatasource', () => {
     });
   });
 
+  describe('When runSql returns an empty dataframe', () => {
+    let ds: MySqlDatasource;
+    const response = {
+      results: {
+        tempvar: {
+          refId: 'tempvar',
+          frames: [],
+        },
+      },
+    };
+
+    beforeEach(async () => {
+      ds = setupTestContext(response).ds;
+    });
+
+    it('should return an empty array when metricFindQuery is called', async () => {
+      const query = 'select * from atable';
+      const results = await ds.metricFindQuery(query);
+      expect(results.length).toBe(0);
+    });
+
+    it('should return an empty array when fetchDatasets is called', async () => {
+      const results = await ds.fetchDatasets();
+      expect(results.length).toBe(0);
+    });
+
+    it('should return an empty array when fetchTables is called', async () => {
+      const results = await ds.fetchTables();
+      expect(results.length).toBe(0);
+    });
+
+    it('should return an empty array when fetchFields is called', async () => {
+      const query: SQLQuery = {
+        refId: 'refId',
+        table: 'schema.table',
+        dataset: 'dataset',
+      };
+      const results = await ds.fetchFields(query);
+      expect(results.length).toBe(0);
+    });
+  });
+
+  describe('When runSql returns a populated dataframe', () => {
+    it('should return a list of datasets when fetchDatasets is called', async () => {
+      const fetchDatasetsResponse = {
+        results: {
+          datasets: {
+            refId: 'datasets',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [{ name: 'name', type: FieldType.string, values: ['test1', 'test2', 'test3'] }],
+                })
+              ),
+            ],
+          },
+        },
+      };
+      const { ds } = setupTestContext(fetchDatasetsResponse);
+
+      const results = await ds.fetchDatasets();
+      expect(results.length).toBe(3);
+      expect(results).toEqual(['test1', 'test2', 'test3']);
+    });
+
+    it('should return a list of tables when fetchTables is called', async () => {
+      const fetchTableResponse = {
+        results: {
+          tables: {
+            refId: 'tables',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [{ name: 'table_name', type: FieldType.string, values: ['test1', 'test2', 'test3'] }],
+                })
+              ),
+            ],
+          },
+        },
+      };
+      const { ds } = setupTestContext(fetchTableResponse);
+
+      const results = await ds.fetchTables();
+      expect(results.length).toBe(3);
+      expect(results).toEqual(['test1', 'test2', 'test3']);
+    });
+
+    it('should return a list of fields when fetchFields is called', async () => {
+      const fetchFieldsResponse = {
+        results: {
+          fields: {
+            refId: 'fields',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [
+                    { name: 'column_name', type: FieldType.string, values: ['test1', 'test2', 'test3'] },
+                    { name: 'data_type', type: FieldType.string, values: ['int', 'char', 'bool'] },
+                  ],
+                })
+              ),
+            ],
+          },
+        },
+      };
+      const { ds } = setupTestContext(fetchFieldsResponse);
+
+      const sqlQuery: SQLQuery = {
+        refId: 'fields',
+        table: 'table',
+        dataset: 'dataset',
+      };
+      const results = await ds.fetchFields(sqlQuery);
+      expect(results.length).toBe(3);
+      expect(results[0].label).toBe('test1');
+      expect(results[0].value).toBe('test1');
+      expect(results[0].type).toBe('int');
+      expect(results[1].label).toBe('test2');
+      expect(results[1].value).toBe('test2');
+      expect(results[1].type).toBe('char');
+      expect(results[2].label).toBe('test3');
+      expect(results[2].value).toBe('test3');
+      expect(results[2].type).toBe('bool');
+    });
+  });
+
   describe('When performing metricFindQuery that returns multiple string fields', () => {
     const query = 'select * from atable';
     const response = {
@@ -88,7 +215,7 @@ describe('MySQLDatasource', () => {
     };
 
     it('should return list of all string field values', async () => {
-      const { ds } = setupTextContext(response);
+      const { ds } = setupTestContext(response);
       const results = await ds.metricFindQuery(query, {});
 
       expect(results.length).toBe(6);
@@ -121,7 +248,7 @@ describe('MySQLDatasource', () => {
     };
 
     it('should return list of all column values', async () => {
-      const { ds, fetchMock } = setupTextContext(response);
+      const { ds, fetchMock } = setupTestContext(response);
       const results = await ds.metricFindQuery(query, { searchFilter: 'aTit' });
 
       expect(fetchMock).toBeCalledTimes(1);
@@ -156,7 +283,7 @@ describe('MySQLDatasource', () => {
     };
 
     it('should return list of all column values', async () => {
-      const { ds, fetchMock } = setupTextContext(response);
+      const { ds, fetchMock } = setupTestContext(response);
       const results = await ds.metricFindQuery(query, {});
 
       expect(fetchMock).toBeCalledTimes(1);
@@ -189,7 +316,7 @@ describe('MySQLDatasource', () => {
     };
 
     it('should return list of as text, value', async () => {
-      const { ds } = setupTextContext(response);
+      const { ds } = setupTestContext(response);
       const results = await ds.metricFindQuery(query, {});
 
       expect(results.length).toBe(3);
@@ -224,7 +351,7 @@ describe('MySQLDatasource', () => {
     };
 
     it('should return list of all field values as text', async () => {
-      const { ds } = setupTextContext(response);
+      const { ds } = setupTestContext(response);
       const results = await ds.metricFindQuery(query, {});
 
       expect(results).toEqual([
@@ -262,7 +389,7 @@ describe('MySQLDatasource', () => {
     };
 
     it('should return list of unique keys', async () => {
-      const { ds } = setupTextContext(response);
+      const { ds } = setupTestContext(response);
       const results = await ds.metricFindQuery(query, {});
 
       expect(results.length).toBe(1);
@@ -274,28 +401,28 @@ describe('MySQLDatasource', () => {
   describe('When interpolating variables', () => {
     describe('and value is a string', () => {
       it('should return an unquoted value', () => {
-        const { ds, variable } = setupTextContext({});
+        const { ds, variable } = setupTestContext({});
         expect(ds.interpolateVariable('abc', variable)).toEqual('abc');
       });
     });
 
     describe('and value is a number', () => {
       it('should return an unquoted value', () => {
-        const { ds, variable } = setupTextContext({});
+        const { ds, variable } = setupTestContext({});
         expect(ds.interpolateVariable(1000, variable)).toEqual(1000);
       });
     });
 
     describe('and value is an array of strings', () => {
       it('should return comma separated quoted values', () => {
-        const { ds, variable } = setupTextContext({});
+        const { ds, variable } = setupTestContext({});
         expect(ds.interpolateVariable(['a', 'b', 'c'], variable)).toEqual("'a','b','c'");
       });
     });
 
     describe('and variable allows multi-value and value is a string', () => {
       it('should return a quoted value', () => {
-        const { ds, variable } = setupTextContext({});
+        const { ds, variable } = setupTestContext({});
         variable.multi = true;
         expect(ds.interpolateVariable('abc', variable)).toEqual("'abc'");
       });
@@ -303,7 +430,7 @@ describe('MySQLDatasource', () => {
 
     describe('and variable contains single quote', () => {
       it('should return a quoted value', () => {
-        const { ds, variable } = setupTextContext({});
+        const { ds, variable } = setupTestContext({});
         variable.multi = true;
         expect(ds.interpolateVariable("a'bc", variable)).toEqual("'a''bc'");
       });
@@ -311,7 +438,7 @@ describe('MySQLDatasource', () => {
 
     describe('and variable allows all and value is a string', () => {
       it('should return a quoted value', () => {
-        const { ds, variable } = setupTextContext({});
+        const { ds, variable } = setupTestContext({});
         variable.includeAll = true;
         expect(ds.interpolateVariable('abc', variable)).toEqual("'abc'");
       });
@@ -320,7 +447,7 @@ describe('MySQLDatasource', () => {
 
   describe('targetContainsTemplate', () => {
     it('given query that contains template variable it should return true', () => {
-      const { ds, templateSrv } = setupTextContext({});
+      const { ds, templateSrv } = setupTestContext({});
       const rawSql = `SELECT
       $__timeGroup(createdAt,'$summarize') as time_sec,
       avg(value) as value,
@@ -347,7 +474,7 @@ describe('MySQLDatasource', () => {
     });
 
     it('given query that only contains global template variable it should return false', () => {
-      const { ds, templateSrv } = setupTextContext({});
+      const { ds, templateSrv } = setupTestContext({});
       const rawSql = `SELECT
       $__timeGroup(createdAt,'$__interval') as time_sec,
       avg(value) as value,

public/app/plugins/datasource/postgres/datasource.test.ts

@@ -7,6 +7,7 @@ import {
   DataQueryResponse,
   DataSourceInstanceSettings,
   dateTime,
+  FieldType,
   LoadingState,
   MutableDataFrame,
 } from '@grafana/data';
@@ -303,6 +304,161 @@ describe('PostgreSQLDatasource', () => {
     });
   });
 
+  describe('When runSql returns an empty dataframe', () => {
+    let ds: PostgresDatasource;
+    const response = {
+      results: {
+        tempvar: {
+          refId: 'tempvar',
+          frames: [],
+        },
+      },
+    };
+
+    beforeEach(async () => {
+      ds = setupTestContext(response).ds;
+    });
+
+    it('should return an empty array when metricFindQuery is called', async () => {
+      const query = 'select * from atable';
+      const results = await ds.metricFindQuery(query);
+      expect(results.length).toBe(0);
+    });
+
+    it('should return an empty array when fetchTables is called', async () => {
+      const results = await ds.fetchTables();
+      expect(results.length).toBe(0);
+    });
+
+    it('should return empty string when getVersion is called', async () => {
+      const results = await ds.getVersion();
+      expect(results).toBe('');
+    });
+
+    it('should return undefined when getTimescaleDBVersion is called', async () => {
+      const results = await ds.getTimescaleDBVersion();
+      expect(results).toBe(undefined);
+    });
+
+    it('should return an empty array when fetchFields is called', async () => {
+      const query: SQLQuery = {
+        refId: 'refId',
+        table: 'schema.table',
+        dataset: 'dataset',
+      };
+      const results = await ds.fetchFields(query);
+      expect(results.length).toBe(0);
+    });
+  });
+
+  describe('When runSql returns a populated dataframe', () => {
+    it('should return a list of tables when fetchTables is called', async () => {
+      const fetchTableResponse = {
+        results: {
+          tables: {
+            refId: 'tables',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [{ name: 'table', type: FieldType.string, values: ['test1', 'test2', 'test3'] }],
+                })
+              ),
+            ],
+          },
+        },
+      };
+
+      const { ds } = setupTestContext(fetchTableResponse);
+
+      const results = await ds.fetchTables();
+      expect(results.length).toBe(3);
+      expect(results).toEqual(['test1', 'test2', 'test3']);
+    });
+
+    it('should return a version string when getVersion is called', async () => {
+      const fetchVersionResponse = {
+        results: {
+          meta: {
+            refId: 'meta',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [{ name: 'version', type: FieldType.string, values: ['test1'] }],
+                })
+              ),
+            ],
+          },
+        },
+      };
+
+      const { ds } = setupTestContext(fetchVersionResponse);
+
+      const version = await ds.getVersion();
+      expect(version).toBe('test1');
+    });
+
+    it('should return a version string when getTimescaleDBVersion is called', async () => {
+      const fetchVersionResponse = {
+        results: {
+          meta: {
+            refId: 'meta',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [{ name: 'extversion', type: FieldType.string, values: ['test1'] }],
+                })
+              ),
+            ],
+          },
+        },
+      };
+
+      const { ds } = setupTestContext(fetchVersionResponse);
+
+      const version = await ds.getTimescaleDBVersion();
+      expect(version).toBe('test1');
+    });
+
+    it('should return a list of fields when fetchFields is called', async () => {
+      const fetchFieldsResponse = {
+        results: {
+          columns: {
+            refId: 'columns',
+            frames: [
+              dataFrameToJSON(
+                new MutableDataFrame({
+                  fields: [
+                    { name: 'column', type: FieldType.string, values: ['test1', 'test2', 'test3'] },
+                    { name: 'type', type: FieldType.string, values: ['int', 'char', 'bool'] },
+                  ],
+                })
+              ),
+            ],
+          },
+        },
+      };
+
+      const { ds } = setupTestContext(fetchFieldsResponse);
+
+      const sqlQuery: SQLQuery = {
+        refId: 'fields',
+        table: 'table',
+        dataset: 'dataset',
+      };
+      const results = await ds.fetchFields(sqlQuery);
+      expect(results.length).toBe(3);
+      expect(results[0].label).toBe('test1');
+      expect(results[0].value).toBe('test1');
+      expect(results[0].type).toBe('int');
+      expect(results[1].label).toBe('test2');
+      expect(results[1].value).toBe('test2');
+      expect(results[1].type).toBe('char');
+      expect(results[2].label).toBe('test3');
+      expect(results[2].value).toBe('test3');
+      expect(results[2].type).toBe('bool');
+    });
+  });
+
   describe('When performing metricFindQuery that returns multiple string fields', () => {
     it('should return list of all string field values', async () => {
       const query = 'select * from atable';

public/app/plugins/datasource/postgres/datasource.ts

@@ -24,19 +24,29 @@ export class PostgresDatasource extends SqlDatasource {
 
   async getVersion(): Promise<string> {
     const value = await this.runSql<{ version: number }>(getVersion());
-    const results = value.fields.version.values.toArray();
+    const results = value.fields.version?.values.toArray();
+
+    if (!results) {
+      return '';
+    }
+
     return results[0].toString();
   }
 
   async getTimescaleDBVersion(): Promise<string | undefined> {
     const value = await this.runSql<{ extversion: string }>(getTimescaleDBVersion());
-    const results = value.fields.extversion.values.toArray();
+    const results = value.fields.extversion?.values.toArray();
+
+    if (!results) {
+      return undefined;
+    }
+
     return results[0];
   }
 
   async fetchTables(): Promise<string[]> {
     const tables = await this.runSql<{ table: string[] }>(showTables(), { refId: 'tables' });
-    return tables.fields.table.values.toArray().flat();
+    return tables.fields.table?.values.toArray().flat() ?? [];
   }
 
   getSqlLanguageDefinition(db: DB): LanguageDefinition {