MySQL, Postgres, MSSQL: Fix validating query with template variables in alert (#19237)

Adds support for validating query in alert for mysql, 
postgres and mssql.

Fixes #13155

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

@@ -160,4 +160,19 @@ export class PostgresDatasource {
         }
       });
   }
+
+  targetContainsTemplate(target: any) {
+    let rawSql = '';
+
+    if (target.rawQuery) {
+      rawSql = target.rawSql;
+    } else {
+      const query = new PostgresQuery(target);
+      rawSql = query.buildQuery();
+    }
+
+    rawSql = rawSql.replace('$__', '');
+
+    return this.templateSrv.variableExists(rawSql);
+  }
 }

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

@@ -3,14 +3,13 @@ import { CustomVariable } from 'app/features/templating/custom_variable';
 import { toUtc, dateTime } from '@grafana/data';
 import { BackendSrv } from 'app/core/services/backend_srv';
 import { IQService } from 'angular';
+import { TemplateSrv } from 'app/features/templating/template_srv';
 
 describe('PostgreSQLDatasource', () => {
   const instanceSettings = { name: 'postgresql' };
 
   const backendSrv = {};
-  const templateSrv: any = {
-    replace: jest.fn(text => text),
-  };
+  const templateSrv: TemplateSrv = new TemplateSrv();
   const raw = {
     from: toUtc('2018-04-25 10:00'),
     to: toUtc('2018-04-25 11:00'),
@@ -249,4 +248,53 @@ describe('PostgreSQLDatasource', () => {
       });
     });
   });
+
+  describe('targetContainsTemplate', () => {
+    it('given query that contains template variable it should return true', () => {
+      const rawSql = `SELECT
+      $__timeGroup("createdAt",'$summarize'),
+      avg(value) as "value",
+      hostname as "metric"
+    FROM
+      grafana_metric
+    WHERE
+      $__timeFilter("createdAt") AND
+      measurement = 'logins.count' AND
+      hostname IN($host)
+    GROUP BY time, metric
+    ORDER BY time`;
+      const query = {
+        rawSql,
+        rawQuery: true,
+      };
+      templateSrv.init([
+        { type: 'query', name: 'summarize', current: { value: '1m' } },
+        { type: 'query', name: 'host', current: { value: 'a' } },
+      ]);
+      expect(ctx.ds.targetContainsTemplate(query)).toBeTruthy();
+    });
+
+    it('given query that only contains global template variable it should return false', () => {
+      const rawSql = `SELECT
+      $__timeGroup("createdAt",'$__interval'),
+      avg(value) as "value",
+      hostname as "metric"
+    FROM
+      grafana_metric
+    WHERE
+      $__timeFilter("createdAt") AND
+      measurement = 'logins.count'
+    GROUP BY time, metric
+    ORDER BY time`;
+      const query = {
+        rawSql,
+        rawQuery: true,
+      };
+      templateSrv.init([
+        { type: 'query', name: 'summarize', current: { value: '1m' } },
+        { type: 'query', name: 'host', current: { value: 'a' } },
+      ]);
+      expect(ctx.ds.targetContainsTemplate(query)).toBeFalsy();
+    });
+  });
 });