From cf2c8cb29385db8bdee00dec384be7598bf3cf17 Mon Sep 17 00:00:00 2001
From: Benjamin Dauvergne <bdauvergne@entrouvert.com>
Date: Thu, 15 Sep 2022 12:25:15 +0200
Subject: [PATCH] sql: load Evolution.parts lazily from database (#69109)

---
 tests/test_sql.py | 30 ++++++++++++++++++++++
 wcs/sql.py        | 63 ++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 92 insertions(+), 1 deletion(-)

diff --git a/tests/test_sql.py b/tests/test_sql.py
index 925c65329..f80a82b6f 100644
--- a/tests/test_sql.py
+++ b/tests/test_sql.py
@@ -1,5 +1,6 @@
 import datetime
 import io
+import pickle
 import random
 import string
 import time
@@ -2248,3 +2249,32 @@ def test_sql_import_zip_create_tables(pub):
     assert table_exists(cur, formdef.table_name)
     conn.commit()
     cur.close()
+
+
+def test_lazyevolutionlist():
+    dump = pickle.dumps([1, 2])
+
+    lazy = sql.LazyEvolutionList(dump)
+    assert len(lazy) == 2
+
+    lazy = sql.LazyEvolutionList(dump)
+    assert str(lazy).startswith('[')
+
+    lazy = sql.LazyEvolutionList(dump)
+    lazy[0] = 'x'
+    assert lazy[0] == 'x'
+
+    lazy = sql.LazyEvolutionList(dump)
+    del lazy[0]
+    assert len(lazy) == 1
+
+    lazy = sql.LazyEvolutionList(dump)
+    lazy += [1]
+    assert len(lazy) == 3
+    assert lazy[2] == 1
+
+    lazy = sql.LazyEvolutionList(dump)
+    assert 1 in lazy
+
+    lazy = sql.LazyEvolutionList(dump)
+    assert list(pickle.loads(pickle.dumps(lazy))) == list(lazy)
diff --git a/wcs/sql.py b/wcs/sql.py
index ac9425d35..33269b16a 100644
--- a/wcs/sql.py
+++ b/wcs/sql.py
@@ -102,6 +102,67 @@ def like_escape(value):
     return value
 
 
+class LazyEvolutionList(list):
+    def __init__(self, dump):
+        self.dump = dump
+
+    def _load(self):
+        try:
+            dump = super().__getattribute__('dump')
+        except AttributeError:
+            pass
+        else:
+            super().__setitem__(slice(0), pickle.loads(dump))
+            del self.dump
+
+    def __getattribute__(self, name):
+        super().__getattribute__('_load')()
+        return super().__getattribute__(name)
+
+    def __bool__(self):
+        self._load()
+        return bool(len(self))
+
+    def __iter__(self):
+        self._load()
+        return super().__iter__()
+
+    def __len__(self):
+        self._load()
+        return super().__len__()
+
+    def __reversed__(self):
+        self._load()
+        return super().__reversed__()
+
+    def __str__(self):
+        self._load()
+        return super().__str__()
+
+    def __getitem__(self, index):
+        self._load()
+        return super().__getitem__(index)
+
+    def __setitem__(self, index, value):
+        self._load()
+        return super().__setitem__(index, value)
+
+    def __delitem__(self, index):
+        self._load()
+        return super().__delitem__(index)
+
+    def __iadd__(self, values):
+        self._load()
+        return super().__add__(values)
+
+    def __contains__(self, value):
+        self._load()
+        return super().__contains__(value)
+
+    def __reduce__(self):
+        return (list, (), None, iter(self))
+
+
 def pickle_loads(value):
     if hasattr(value, 'tobytes'):
         value = value.tobytes()
@@ -2576,7 +2637,7 @@ class SqlDataMixin(SqlMixin):
         if o.time:
             o.time = o.time.timetuple()
         if row[6]:
-            o.parts = pickle_loads(row[6])
+            o.parts = LazyEvolutionList(row[6])
         return o
 
     def set_evolution(self, value):
-- 
2.37.2