Firebird 2 has a SUBSTRING() builtin, expose it thru a function

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/sqlalchemy/databases/firebird.py b/lib/sqlalchemy/databases/firebird.py
index 11a88bf18..5e1dd72bb 100644
--- a/lib/sqlalchemy/databases/firebird.py
+++ b/lib/sqlalchemy/databases/firebird.py
@@ -547,6 +547,15 @@ class FBDialect(default.DefaultDialect):
         connection.commit(True)
 
 
+def _substring(s, start, length=None):
+    "Helper function to handle Firebird 2 SUBSTRING builtin"
+
+    if length is None:
+        return "SUBSTRING(%s FROM %s)" % (s, start)
+    else:
+        return "SUBSTRING(%s FROM %s FOR %s)" % (s, start, length)
+
+
 class FBCompiler(sql.compiler.DefaultCompiler):
     """Firebird specific idiosincrasies"""
 
@@ -564,6 +573,9 @@ class FBCompiler(sql.compiler.DefaultCompiler):
         else:
             return self.process(alias.original, **kwargs)
 
+    functions = sql.compiler.DefaultCompiler.functions.copy()
+    functions['substring'] = _substring
+
     def function_argspec(self, func):
         if func.clauses:
             return self.process(func.clause_expr)