From 103260ddb476c5354b3201f92636c474f2a83c35 Mon Sep 17 00:00:00 2001
From: RobotScribe <quentinso@theodo.fr>
Date: Wed, 29 Apr 2020 15:22:59 -0400
Subject: Add with_for_update mysql new functionalities

Fixes: #4860

# Description
Add nowait, skip_lock, of arguments to for_update_clause for mysql

### Checklist

This pull request is:

- [ ] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [ ] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [x] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

**Have a nice day!**

Closes: #5290
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5290
Pull-request-sha: 490e822e73e92ffe63cf45df9c49f3b31af1954d

Change-Id: Ibd2acc47b538c601c69c8fb954776035ecab4c6c
---
 lib/sqlalchemy/dialects/mysql/base.py | 31 +++++++++++++++++++++++++++++--
 lib/sqlalchemy/engine/default.py      |  3 +++
 2 files changed, 32 insertions(+), 2 deletions(-)

(limited to 'lib/sqlalchemy')

diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py
index dca7b9a00..d009d656e 100644
--- a/lib/sqlalchemy/dialects/mysql/base.py
+++ b/lib/sqlalchemy/dialects/mysql/base.py
@@ -808,6 +808,7 @@ from ...sql import coercions
 from ...sql import compiler
 from ...sql import elements
 from ...sql import roles
+from ...sql import util as sql_util
 from ...types import BINARY
 from ...types import BLOB
 from ...types import BOOLEAN
@@ -1494,9 +1495,28 @@ class MySQLCompiler(compiler.SQLCompiler):
 
     def for_update_clause(self, select, **kw):
         if select._for_update_arg.read:
-            return " LOCK IN SHARE MODE"
+            tmp = " LOCK IN SHARE MODE"
         else:
-            return " FOR UPDATE"
+            tmp = " FOR UPDATE"
+
+        if select._for_update_arg.of and self.dialect.supports_for_update_of:
+
+            tables = util.OrderedSet()
+            for c in select._for_update_arg.of:
+                tables.update(sql_util.surface_selectables_only(c))
+
+            tmp += " OF " + ", ".join(
+                self.process(table, ashint=True, use_schema=False, **kw)
+                for table in tables
+            )
+
+        if select._for_update_arg.nowait:
+            tmp += " NOWAIT"
+
+        if select._for_update_arg.skip_locked and self.dialect._is_mysql:
+            tmp += " SKIP LOCKED"
+
+        return tmp
 
     def limit_clause(self, select, **kw):
         # MySQL supports:
@@ -2211,6 +2231,9 @@ class MySQLDialect(default.DefaultDialect):
 
     sequences_optional = True
 
+    supports_for_update_of = False  # default for MySQL ...
+    # ... may be updated to True for MySQL 8+ in initialize()
+
     supports_sane_rowcount = True
     supports_sane_multi_rowcount = False
     supports_multivalues_insert = True
@@ -2526,6 +2549,10 @@ class MySQLDialect(default.DefaultDialect):
             self._is_mariadb and self.server_version_info >= (10, 3)
         )
 
+        self.supports_for_update_of = (
+            self._is_mysql and self.server_version_info >= (8,)
+        )
+
         self._needs_correct_for_88718_96365 = (
             not self._is_mariadb and self.server_version_info >= (8,)
         )
diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 20f731116..b17549668 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -128,6 +128,9 @@ class DefaultDialect(interfaces.Dialect):
 
     supports_server_side_cursors = False
 
+    # extra record-level locking features (#4860)
+    supports_for_update_of = False
+
     server_version_info = None
 
     default_schema_name = None
-- 
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