Add SQL query for currency by date range

issue6944
review42851002

CHANGELOG

@@ -1,3 +1,4 @@
+* Add SQL query for currency by date range
 * Remove monetary formatting from currency
 
 Version 4.6.0 - 2017-10-30

currency.py

@@ -4,6 +4,9 @@ import datetime
 
 from decimal import Decimal, ROUND_HALF_EVEN
 
+from sql import Window
+from sql.functions import NthValue
+
 from trytond import backend
 from trytond.model import ModelView, ModelSQL, fields, Unique, Check
 from trytond.tools import datetime_strftime
@@ -175,6 +178,40 @@ class Currency(ModelSQL, ModelView):
         else:
             return amount * to_currency.rate / from_currency.rate
 
+    @classmethod
+    def currency_rate_sql(cls):
+        "Return a SQL query with currency, rate, start_date and end_date"
+        pool = Pool()
+        Rate = pool.get('currency.currency.rate')
+        transaction = Transaction()
+        database = transaction.database
+
+        rate = Rate.__table__()
+        if database.has_window_functions():
+            window = Window(
+                [rate.currency],
+                order_by=[rate.date.asc],
+                frame='ROWS', start=0, end=1)
+            # Use NthValue instead of LastValue to get NULL for the last row
+            end_date = NthValue(rate.date, 2, window=window)
+        else:
+            next_rate = Rate.__table__()
+            end_date = next_rate.select(
+                next_rate.date,
+                where=(next_rate.currency == rate.currency)
+                & (next_rate.date > rate.date),
+                order_by=[next_rate.date.asc],
+                limit=1)
+
+        query = (rate
+            .select(
+                rate.currency.as_('currency'),
+                rate.rate.as_('rate'),
+                rate.date.as_('start_date'),
+                end_date.as_('end_date'),
+                ))
+        return query
+
 
 class Rate(ModelSQL, ModelView):
     'Rate'

tests/test_currency.py

@@ -1,8 +1,10 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
+import datetime
 import unittest
 from decimal import Decimal
 import trytond.tests.test_tryton
+from trytond.transaction import Transaction
 from trytond.tests.test_tryton import ModuleTestCase, with_transaction
 from trytond.pool import Pool
 
@@ -17,12 +19,15 @@ def create_currency(name):
                 }])[0]
 
 
-def add_currency_rate(currency, rate):
+def add_currency_rate(currency, rate, date=None):
     pool = Pool()
     Rate = pool.get('currency.currency.rate')
+    if date is None:
+        date = Rate.default_date()
     return Rate.create([{
                 'currency': currency.id,
                 'rate': rate,
+                'date': date,
                 }])[0]
 
 
@@ -213,6 +218,40 @@ class CurrencyTestCase(ModuleTestCase):
                     )], 0, None, None)
         self.assertFalse(rates)
 
+    @with_transaction()
+    def test_currency_rate_sql(self):
+        "Test currency rate SQL"
+        pool = Pool()
+        Currency = pool.get('currency.currency')
+        transaction = Transaction()
+        cursor = transaction.connection.cursor()
+        date = datetime.date
+
+        cu1 = create_currency('cu1')
+        for date_, rate in [
+                (date(2017, 1, 1), Decimal(1)),
+                (date(2017, 2, 1), Decimal(2)),
+                (date(2017, 3, 1), Decimal(3))]:
+            add_currency_rate(cu1, rate, date_)
+        cu2 = create_currency('cu2')
+        for date_, rate in [
+                (date(2017, 2, 1), Decimal(2)),
+                (date(2017, 4, 1), Decimal(4))]:
+            add_currency_rate(cu2, rate, date_)
+
+        query = Currency.currency_rate_sql()
+        cursor.execute(*query)
+        data = set(cursor.fetchall())
+        result = {
+            (cu1.id, Decimal(1), date(2017, 1, 1), date(2017, 2, 1)),
+            (cu1.id, Decimal(2), date(2017, 2, 1), date(2017, 3, 1)),
+            (cu1.id, Decimal(3), date(2017, 3, 1), None),
+            (cu2.id, Decimal(2), date(2017, 2, 1), date(2017, 4, 1)),
+            (cu2.id, Decimal(4), date(2017, 4, 1), None),
+            }
+
+        self.assertSetEqual(data, result)
+
 
 def suite():
     suite = trytond.tests.test_tryton.suite()