From: Joshua Morris <joshuajohnmorris@gmail.com>
Date: Sun, 4 Jun 2023 09:52:21 +0000 (+1000)
Subject: Add support for `string_agg` with MySQL backend
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=744e1be1b31e02dcb0caa1175d36d74c996f370c;p=thirdparty%2Fsqlalchemy%2Fsqlalchemy.git

Add support for `string_agg` with MySQL backend
---

diff --git a/lib/sqlalchemy/dialects/mysql/base.py b/lib/sqlalchemy/dialects/mysql/base.py
index 0a68b3779e..4712c9b402 100644
--- a/lib/sqlalchemy/dialects/mysql/base.py
+++ b/lib/sqlalchemy/dialects/mysql/base.py
@@ -1208,6 +1208,15 @@ class MySQLCompiler(compiler.SQLCompiler):
         )
         return f"{clause} WITH ROLLUP"
 
+    def visit_string_agg_func(self, fn, **kw):
+        if len(fn.clauses) > 1:
+            return "group_concat(%s SEPARATOR %s)" % (
+                fn.clauses[0]._compiler_dispatch(self, **kw),
+                fn.clauses[-1]._compiler_dispatch(self, **kw),
+            )
+        else:
+            return "group_concat%s" % self.function_argspec(fn)
+
     def visit_sequence(self, seq, **kw):
         return "nextval(%s)" % self.preparer.format_sequence(seq)
 
diff --git a/lib/sqlalchemy/sql/elements.py b/lib/sqlalchemy/sql/elements.py
index ba074db80c..ad5fcde1ae 100644
--- a/lib/sqlalchemy/sql/elements.py
+++ b/lib/sqlalchemy/sql/elements.py
@@ -2766,6 +2766,9 @@ class ClauseList(
         self._is_implicitly_boolean = False
         return self
 
+    def __getitem__(self, item) -> ColumnElement[Any]:
+        return self.clauses[item]
+
     def __iter__(self) -> Iterator[ColumnElement[Any]]:
         return iter(self.clauses)
 
diff --git a/test/sql/test_functions.py b/test/sql/test_functions.py
index 51ed638940..c15b763888 100644
--- a/test/sql/test_functions.py
+++ b/test/sql/test_functions.py
@@ -242,6 +242,14 @@ class CompileTest(fixtures.TestBase, AssertsCompiledSQL):
             literal_binds=True,
             render_postcompile=True,
         )
+        self.assert_compile(
+            stmt,
+            "SELECT group_concat(t.value SEPARATOR ',') "
+            "AS string_agg_1 FROM t",
+            dialect=mysql.dialect(),
+            literal_binds=True,
+            render_postcompile=True,
+        )
 
     def test_cube_operators(self):
         t = table(