PostgreSQL performance optimization (#4457)

Performance-optimizing transactions to execute all non-result queries as a single operation.

Author: vitaly-t

src/Adapters/Storage/Postgres/PostgresStorageAdapter.js

@@ -809,7 +809,8 @@ export class PostgresStorageAdapter implements StorageAdapter {
           return list.concat(joinTablesForSchema(schema.schema));
         }, []);
         const classes = ['_SCHEMA', '_PushStatus', '_JobStatus', '_JobSchedule', '_Hooks', '_GlobalConfig', '_Audience', ...results.map(result => result.className), ...joins];
-        return this._client.tx(t=>t.batch(classes.map(className=>t.none('DROP TABLE IF EXISTS $<className:name>', {className}))));
+        const queries = classes.map(className => ({query: 'DROP TABLE IF EXISTS $<className:name>', values: {className}}));
+        return this._client.tx(t => t.none(this._pgp.helpers.concat(queries)));
       }, error => {
         if (error.code === PostgresRelationDoesNotExistError) {
           // No _SCHEMA collection. Don't delete anything.
@@ -1604,7 +1605,8 @@ export class PostgresStorageAdapter implements StorageAdapter {
   }
 
   dropIndexes(className: string, indexes: any, conn: any): Promise<void> {
-    return (conn || this._client).tx(t => t.batch(indexes.map(i => t.none('DROP INDEX $1:name', i))));
+    const queries = indexes.map(i => ({query: 'DROP INDEX $1:name', values: i}));
+    return (conn || this._client).tx(t => t.none(this._pgp.helpers.concat(queries)));
   }
 
   getIndexes(className: string) {