From fa427f15b71ce13fc91cc39b852a9c70c1c6da7e Mon Sep 17 00:00:00 2001
From: Raphael Collet <rco@openerp.com>
Date: Fri, 4 Sep 2015 16:09:56 +0200
Subject: [PATCH] =?UTF-8?q?[FIX]=20models:=20performance=20of=20`mapped`?=
 =?UTF-8?q?=20is=20now=20in=20O(n)=20instead=20of=20O(n=C2=B2)?=
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---
 openerp/models.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/openerp/models.py b/openerp/models.py
index fe901078e62..38d4423f3e7 100644
--- a/openerp/models.py
+++ b/openerp/models.py
@@ -5363,7 +5363,11 @@ class BaseModel(object):
         """
         if self:
             vals = [func(rec) for rec in self]
-            return reduce(operator.or_, vals) if isinstance(vals[0], BaseModel) else vals
+            if isinstance(vals[0], BaseModel):
+                # return the union of all recordsets in O(n)
+                ids = set(itertools.chain(*[rec._ids for rec in vals]))
+                return vals[0].browse(ids)
+            return vals
         else:
             vals = func(self)
             return vals if isinstance(vals, BaseModel) else []