From 6104ab4db4d776303d5e4c604f72e47887ef2c07 Mon Sep 17 00:00:00 2001
From: Benjamin Dauvergne <bdauvergne@entrouvert.com>
Date: Tue, 5 Oct 2021 22:18:08 +0200
Subject: [PATCH 1/3] sql: use a for loop to iterate on cursors

cursor.fetchone() disable prefetching by named cursors. It forces one
row at a time iterations and using a while loop is a bizarre idiom for
psycopg2 since cursor are perfectly iterable.
---
 wcs/sql.py | 36 ++++++++----------------------------
 1 file changed, 8 insertions(+), 28 deletions(-)

diff --git a/wcs/sql.py b/wcs/sql.py
index 684b17a1..57f9b16e 100644
--- a/wcs/sql.py
+++ b/wcs/sql.py
@@ -1227,10 +1227,7 @@ def drop_views(formdef, conn, cur):
             ('wcs\\_view\\_%',),
         )
     view_names = []
-    while True:
-        row = cur.fetchone()
-        if row is None:
-            break
+    for row in cur:
         view_names.append(row[0])
 
     for view_name in view_names:
@@ -1357,10 +1354,7 @@ def drop_global_views(conn, cur):
         ('wcs\\_category\\_%',),
     )
     view_names = []
-    while True:
-        row = cur.fetchone()
-        if row is None:
-            break
+    for row in cur:
         view_names.append(row[0])
 
     for view_name in view_names:
@@ -1382,10 +1376,7 @@ def do_global_views(conn, cur):
         ('wcs\\_view\\_%',),
     )
     existing_views = set()
-    while True:
-        row = cur.fetchone()
-        if row is None:
-            break
+    for row in cur:
         existing_views.add(row[0])
 
     view_names = existing_views.intersection(view_names)
@@ -1482,10 +1473,7 @@ class SqlMixin:
             parameters['offset'] = offset
         cur.execute(sql_statement, parameters)
         try:
-            while True:
-                row = cur.fetchone()
-                if row is None:
-                    break
+            for row in cur:
                 ob = cls._row2ob(row)
                 if ignore_errors and ob is None:
                     continue
@@ -1611,10 +1599,7 @@ class SqlMixin:
 
     @classmethod
     def get_objects_iterator(cls, cur, ignore_errors=False, extra_fields=None):
-        while True:
-            row = cur.fetchone()
-            if row is None:
-                break
+        for row in cur:
             yield cls._row2ob(row, extra_fields=extra_fields)
 
     @classmethod
@@ -1672,6 +1657,7 @@ class SqlMixin:
         if cls._iterate_on_server:
             conn = get_connection(isolate=True)
             cur = conn.cursor(name='select_iterator_%s' % uuid.uuid4())
+            cur.itersize = 1
         else:
             conn, cur = get_connection_and_cursor()
         cur.execute(sql_statement, parameters)
@@ -1922,10 +1908,7 @@ class SqlDataMixin(SqlMixin):
         )
         cur.execute(sql_statement, {'id': self.id})
         self._evolution = []
-        while True:
-            row = cur.fetchone()
-            if row is None:
-                break
+        for row in cur:
             self._evolution.append(self._row2evo(row, formdata=self))
         conn.commit()
         cur.close()
@@ -1973,10 +1956,7 @@ class SqlDataMixin(SqlMixin):
         for value in values:
             value._evolution = []
 
-        while True:
-            row = cur.fetchone()
-            if row is None:
-                break
+        for row in cur:
             formdata_id = tuple(row[:8])[7]
             formdata = object_dict.get(formdata_id)
             if not formdata:
-- 
2.33.0