Some code-level docs for r3916

diff --git a/lib/sqlalchemy/databases/mysql.py b/lib/sqlalchemy/databases/mysql.py
index ba0ad5e0af520ed9556916d5d0b087616a21e13e..122c24bff51499fdbefc12fee55de9245342b94c 100644 (file)
--- a/lib/sqlalchemy/databases/mysql.py
+++ b/lib/sqlalchemy/databases/mysql.py
@@ -1882,6 +1882,11 @@ class MySQLCompiler(compiler.DefaultCompiler):
             return ""
 
     def visit_join(self, join, asfrom=False, **kwargs):
+        # 'JOIN ... ON ...' for inner joins isn't available until 4.0.
+        # Apparently < 3.23.17 requires theta joins for inner joins
+        # (but not outer).  Not generating these currently, but
+        # support can be added, preferably after dialects are
+        # refactored to be version-sensitive.
         return ''.join(
             (self.process(join.left, asfrom=True),
              (join.isouter and " LEFT OUTER JOIN " or " INNER JOIN "),