Mention MySQL foreign key constraint limitations

1 files changed, 22 insertions, 0 deletions

diff --git a/doc/manual.xhtml b/doc/manual.xhtml
index 20bdf89..6c1c57c 100644
--- a/doc/manual.xhtml
+++ b/doc/manual.xhtml
@@ -535,6 +535,13 @@ for consistency.
           <tr><th>12.2</th><td><a href="#12.2">MySQL Database Class</a></td></tr>
           <tr><th>12.3</th><td><a href="#12.3">MySQL Connection and Connection Factory</a></td></tr>
 	  <tr><th>12.4</th><td><a href="#12.4">MySQL Exceptions</a></td></tr>
+	  <tr>
+            <th>12.5</th><td><a href="#12.5">MySQL Limitations</a>
+              <table class="toc">
+                <tr><th>12.5.1</th><td><a href="#12.5.1">Foreign Key Constraints</a></td></tr>
+              </table>
+            </td>
+          </tr>
         </table>
       </td>
     </tr>
@@ -10195,6 +10202,21 @@ namespace odb
      <code>what()</code> function returns a human-readable description
      of an error.</p>
 
+  <h2><a name="12.5">12.5 MySQL Limitations</a></h2>
+
+  <p>The following sections describe MySQL-specific limitations imposed
+     by the current MySQL and ODB runtime versions.</p>
+
+  <h3><a name="12.5.1">12.5.1 Foreign Key Constraints</a></h3>
+
+  <p>ODB relies on standard SQL behavior which requires that foreign
+     key constraints checking is deferred until the transaction is
+     committed. The only behaviors supported by MySQL are to either
+     check such constraints immediately (InnoDB engine) or to ignore
+     foreign key constraints altogether (all other engines). As a
+     result, schemas generated by the ODB compiler for MySQL have
+     foreign key definitions commented out. They are retained only
+     for documentation.</p>
 
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