[ADD] pg.query_ids: query large numbers of ids memory-safely

This is mainly the code that has been recently added to `orm.recompute_fields`,
here we're making it re-usasble.

Author: cawo-odoo

src/util/pg.py

@@ -1932,3 +1932,49 @@ def bulk_update_table(cr, table, columns, mapping, key_col="id"):
         key_col=key_col,
     )
     cr.execute(query, [Json(mapping)])
+
+
+class query_ids(object):
+    def __init__(self, cr, query, itersize=None):
+        self._cr = cr
+        self._tmp_tbl = "_upgrade_query_ids_{}".format(uuid.uuid4().hex)
+        cr.execute(
+            format_query(
+                cr,
+                "CREATE UNLOGGED TABLE {}(id) AS (WITH query AS ({}) SELECT * FROM query)",
+                self._tmp_tbl,
+                SQLStr(query),
+            )
+        )
+        self._len = cr.rowcount
+        cr.execute(
+            format_query(
+                cr, "ALTER TABLE {} ADD CONSTRAINT {} PRIMARY KEY (id)", self._tmp_tbl, "pk_{}_id".format(self._tmp_tbl)
+            )
+        )
+        self._ncr = named_cursor(cr, itersize)
+        self._ncr.execute(format_query(cr, "SELECT id FROM {} ORDER BY id", self._tmp_tbl))
+
+    def _drop_tmp_tbl(self):
+        if self._cr:
+            self._cr.execute(format_query(self._cr, "DROP TABLE IF EXISTS {}", self._tmp_tbl))
+            self._cr = None
+
+    def __len__(self):
+        return self._len
+
+    def __iter__(self):
+        return (id_ for (id_,) in self._ncr)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self._ncr.__exit__(exc_type, exc_value, traceback)
+        self._drop_tmp_tbl()
+        return False
+
+    def __del__(self):
+        self._ncr.close()
+        del self._ncr
+        self._drop_tmp_tbl()