[IMP] base: reduce new DB size by ordering columns

Postgres is aligning columns to 4 or 8 bytes, depending on their type.
So, consecutive fixed-length columns of differing size will be padded
with empty bytes due to the alignment requirements.

Before this patch, columns where created in their definition order. Now,
they are ordered based on their size, in order to minimize the padding.

As an example, before each row uses 36 bytes (+24b header):

       attname   |  typname  | typlen
    -------------+-----------+--------
     id          | int4      |      4
     create_uid  | int4      |      4
     create_date | timestamp |      8
     write_uid   | int4      |      4    -> 4 bytes padding
     write_date  | timestamp |      8
     active      | bool      |      1    -> 3 bytes padding

After each row uses 32 bytes (4 bytes saved per row):

       attname   |  typname  | typlen
    -------------+-----------+--------
     id          | int4      |      4
     create_uid  | int4      |      4
     write_uid   | int4      |      4
     active      | bool      |      1    -> 3 bytes padding
     create_date | timestamp |      8
     write_date  | timestamp |      8

This saving scheme applies to all rows in all tables. We save between 4
and 8 bytes per row just on the usual create_uid, create_date,
write_uid, write_date.

closes odoo/odoo#87896

Signed-off-by: Raphael Collet <rco@odoo.com>

odoo/addons/base/data/base_data.sql

@@ -14,14 +14,14 @@ CREATE TABLE ir_act_client (primary key(id)) INHERITS (ir_actions);
 
 CREATE TABLE res_users (
     id serial NOT NULL,
-    active boolean default True,
-    login varchar(64) NOT NULL UNIQUE,
-    password varchar default null,
     -- No FK references below, will be added later by ORM
     -- (when the destination rows exist)
     company_id integer, -- references res_company,
     partner_id integer, -- references res_partner,
+    active boolean default True,
     create_date timestamp without time zone,
+    login varchar(64) NOT NULL UNIQUE,
+    password varchar default null,
     primary key(id)
 );
 
@@ -86,11 +86,11 @@ CREATE TABLE ir_model_data (
     create_date timestamp without time zone DEFAULT (now() at time zone 'UTC'),
     write_date timestamp without time zone DEFAULT (now() at time zone 'UTC'),
     write_uid integer,
+    res_id integer,
     noupdate boolean DEFAULT False,
     name varchar NOT NULL,
     module varchar NOT NULL,
     model varchar NOT NULL,
-    res_id integer,
     primary key(id)
 );
 
@@ -113,9 +113,9 @@ CREATE TABLE res_company (
 
 CREATE TABLE res_partner (
     id serial,
-    name varchar,
     company_id integer,
     create_date timestamp without time zone,
+    name varchar,
     primary key(id)
 );
 

odoo/fields.py

@@ -21,7 +21,7 @@ import pytz
 from .tools import (
     float_repr, float_round, float_compare, float_is_zero, html_sanitize, human_size,
     pg_varchar, ustr, OrderedSet, pycompat, sql, date_utils, unique,
-    image_process, merge_sequences,
+    image_process, merge_sequences, SQL_ORDER_BY_TYPE,
 )
 from .tools import DEFAULT_SERVER_DATE_FORMAT as DATE_FORMAT
 from .tools import DEFAULT_SERVER_DATETIME_FORMAT as DATETIME_FORMAT
@@ -937,6 +937,11 @@ class Field(MetaField('DummyField', (object,), {})):
     # Update database schema
     #
 
+    @property
+    def column_order(self):
+        """ Prescribed column order in table. """
+        return 0 if self.column_type is None else SQL_ORDER_BY_TYPE[self.column_type[0]]
+
     def update_db(self, model, columns):
         """ Update the database schema to implement this field.
 

odoo/models.py

@@ -2850,9 +2850,9 @@ class BaseModel(metaclass=MetaModel):
                     return field.column_type[1] + (" NOT NULL" if field.required else "")
 
                 tools.create_model_table(cr, self._table, self._description, [
-                    (name, make_type(field), field.string)
-                    for name, field in self._fields.items()
-                    if name != 'id' and field.store and field.column_type
+                    (field.name, make_type(field), field.string)
+                    for field in sorted(self._fields.values(), key=lambda f: f.column_order)
+                    if field.name != 'id' and field.store and field.column_type
                 ])
 
             if self._parent_store:
@@ -2868,7 +2868,7 @@ class BaseModel(metaclass=MetaModel):
             columns = tools.table_columns(cr, self._table)
             fields_to_compute = []
 
-            for field in self._fields.values():
+            for field in sorted(self._fields.values(), key=lambda f: f.column_order):
                 if not field.store:
                     continue
                 if field.manual and not update_custom_fields:

odoo/tools/sql.py

@@ -6,6 +6,7 @@
 import logging
 import psycopg2
 import odoo.sql_db
+from collections import defaultdict
 from contextlib import closing
 
 _schema = logging.getLogger('odoo.schema')
@@ -50,6 +51,17 @@ def table_kind(cr, tablename):
     cr.execute(query, (tablename,))
     return cr.fetchone()[0] if cr.rowcount else None
 
+# prescribed column order by type size: 4 bytes, 1 byte, 8 bytes, variable size
+# (values have been chosen to minimize padding in rows; unknown column types
+# are considered variable size and put last)
+SQL_ORDER_BY_TYPE = defaultdict(lambda: 6, {
+    'int4': 1,        # 4 bytes
+    'date': 2,        # 4 bytes
+    'bool': 3,        # 1 byte
+    'float8': 4,      # 8 bytes
+    'timestamp': 5,   # 8 bytes
+})
+
 def create_model_table(cr, tablename, comment=None, columns=()):
     """ Create the table for a model. """
     colspecs = ['id SERIAL NOT NULL'] + [