From b59090f44d39176a7f5b097d88278d1074080f50 Mon Sep 17 00:00:00 2001
From: clarkdave <me@clarkdave.net>
Date: Wed, 28 Nov 2018 10:17:03 +0000
Subject: [PATCH] add `lock` method to SelectQueryBuilder

https://github.com/typeorm/typeorm/issues/2037
---
 src/query-builder/QueryExpressionMap.ts |  6 ++++++
 src/query-builder/SelectQueryBuilder.ts | 22 +++++++++++++++-------
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/src/query-builder/QueryExpressionMap.ts b/src/query-builder/QueryExpressionMap.ts
index 42f1f61642..1972efaffb 100644
--- a/src/query-builder/QueryExpressionMap.ts
+++ b/src/query-builder/QueryExpressionMap.ts
@@ -163,6 +163,12 @@ export class QueryExpressionMap {
      */
     withDeleted: boolean = false;
 
+    /**
+     * Locking clause.
+     * 
+     */
+    lockClause?: string;
+
     /**
      * Parameters used to be escaped in final query.
      */
diff --git a/src/query-builder/SelectQueryBuilder.ts b/src/query-builder/SelectQueryBuilder.ts
index 4b8a8d71b2..5e9b2483a4 100644
--- a/src/query-builder/SelectQueryBuilder.ts
+++ b/src/query-builder/SelectQueryBuilder.ts
@@ -1019,6 +1019,16 @@ export class SelectQueryBuilder<Entity> extends QueryBuilder<Entity> implements
         return this;
     }
 
+    /**
+     * Set a lock clause, passed directly into the query.
+     * e.g. `FOR UPDATE NOWAIT`.
+     * If set, will override `lockMode`.
+     */
+    lock(clause: string): this {
+        this.expressionMap.lockClause = clause;
+        return this;
+    }
+
     /**
      * Gets first raw result returned by execution of generated query builder sql.
      */
@@ -1055,13 +1065,6 @@ export class SelectQueryBuilder<Entity> extends QueryBuilder<Entity> implements
 
         } catch (error) {
 
-            // rollback transaction if we started it
-            if (transactionStartedByUs) {
-                try {
-                    await queryRunner.rollbackTransaction();
-                } catch (rollbackError) { }
-            }
-            throw error;
 
         } finally {
             if (queryRunner !== this.queryRunner) { // means we created our own query runner
@@ -1690,6 +1693,11 @@ export class SelectQueryBuilder<Entity> extends QueryBuilder<Entity> implements
      */
     protected createLockExpression(): string {
         const driver = this.connection.driver;
+
+        if (this.expressionMap.lockClause) {
+            return ` ${this.expressionMap.lockClause}`;
+        }
+
         switch (this.expressionMap.lockMode) {
             case "pessimistic_read":
                 if (driver instanceof MysqlDriver || driver instanceof AuroraDataApiDriver) {