[FIX] recompute_fields: get ids in batches

If no ids are given to recompute, the util will fetch
all ids in the target table and then recompute in chunks.
Fetching all the ids itself can cause a memory error
if the table is too large.
Using a named cursor with a limit of 1M records to fetch
can eliminate this possibility.

closes #303

Signed-off-by: Christophe Simonis (chs) <chs@odoo.com>

Author: jjmaksoud

src/util/orm.py

@@ -14,7 +14,6 @@
 from contextlib import contextmanager
 from functools import wraps
 from itertools import chain
-from operator import itemgetter
 from textwrap import dedent
 
 try:
@@ -43,7 +42,7 @@
 from .exceptions import MigrationError
 from .helpers import table_of_model
 from .misc import chunks, log_progress, version_between, version_gte
-from .pg import column_exists, get_columns
+from .pg import column_exists, format_query, get_columns, named_cursor
 
 # python3 shims
 try:
@@ -281,18 +280,31 @@ def recompute_fields(cr, model, fields, ids=None, logger=_logger, chunk_size=256
     assert strategy in {"flush", "commit", "auto"}
     Model = env(cr)[model] if isinstance(model, basestring) else model
     model = Model._name
+
+    def get_ids():
+        if ids is not None:
+            for id_ in ids:
+                yield id_
+        else:
+            with named_cursor(cr, itersize=2**20) as ncr:
+                ncr.execute(format_query(cr, "SELECT id FROM {t} ORDER BY id", t=table_of_model(cr, model)))
+                for (id_,) in ncr:
+                    yield id_
+
     if ids is None:
-        cr.execute('SELECT id FROM "%s"' % table_of_model(cr, model))
-        ids = tuple(map(itemgetter(0), cr.fetchall()))
+        cr.execute(format_query(cr, "SELECT COUNT(id) FROM {t}", t=table_of_model(cr, model)))
+        (count,) = cr.fetchone()
+    else:
+        count = len(ids)
 
     if strategy == "auto":
-        big_table = len(ids) > BIG_TABLE_THRESHOLD
+        big_table = count > BIG_TABLE_THRESHOLD
         any_tracked_field = any(getattr(Model._fields[f], _TRACKING_ATTR, False) for f in fields)
         strategy = "commit" if big_table and any_tracked_field else "flush"
 
-    size = (len(ids) + chunk_size - 1) / chunk_size
+    size = (count + chunk_size - 1) / chunk_size
     qual = "%s %d-bucket" % (model, chunk_size) if chunk_size != 1 else model
-    for subids in log_progress(chunks(ids, chunk_size, list), logger, qualifier=qual, size=size):
+    for subids in log_progress(chunks(get_ids(), chunk_size, list), logger, qualifier=qual, size=size):
         records = Model.browse(subids)
         for field_name in fields:
             field = records._fields[field_name]