Add an option to dynamically get the view sql

Author: mikicz

README.md

@@ -261,6 +261,30 @@ class PreferredCustomer(pg.View):
       managed = False
 ```
 
+### Dynamic View SQL
+
+If you need a dynamic view SQL (for example if it needs a value from settings in it), you can override the `run_sql`
+classmethod on the view to return the SQL. The method should return a namedtuple `ViewSQL`, which contains the query
+and potentially the params to `cursor.execute` call. Params should be either None or a list of parameters for the query.
+
+```python
+from django.conf import settings
+from django_pgviews import view as pg
+
+
+class PreferredCustomer(pg.View):
+    @classmethod
+    def get_sql(cls):
+        return pg.ViewSQL(
+            """SELECT * FROM myapp_customer WHERE is_preferred = TRUE and created_at >= %s;""",
+            [settings.MIN_PREFERRED_CUSTOMER_CREATED_AT]
+        )
+
+    class Meta:
+      db_table = 'preferredcustomer'
+      managed = False
+```
+
 ### Sync Listeners
 
 django-pgviews 0.5.0 adds the ability to listen to when a `post_sync` event has

django_pgviews/models.py

@@ -51,7 +51,7 @@ def run_backlog(self, models, force, update):
                 status = create_view(
                     connection,
                     view_cls._meta.db_table,
-                    view_cls.sql,
+                    view_cls.get_sql(),
                     update=update,
                     force=force,
                     materialized=isinstance(view_cls(), MaterializedView),

django_pgviews/view.py

@@ -18,6 +18,8 @@
 FIELD_SPEC_REGEX = r"^([A-Za-z_][A-Za-z0-9_]*)\." r"([A-Za-z_][A-Za-z0-9_]*)\." r"(\*|(?:[A-Za-z_][A-Za-z0-9_]*))$"
 FIELD_SPEC_RE = re.compile(FIELD_SPEC_REGEX)
 
+ViewSQL = collections.namedtuple("ViewSQL", "query,params")
+
 log = logging.getLogger("django_pgviews.view")
 
 
@@ -62,7 +64,7 @@ def realize_deferred_projections(sender, *args, **kwargs):
 
 
 @transaction.atomic()
-def create_view(connection, view_name, view_query, update=True, force=False, materialized=False, index=None):
+def create_view(connection, view_name, view_query: ViewSQL, update=True, force=False, materialized=False, index=None):
     """
     Create a named view on a connection.
 
@@ -98,27 +100,32 @@ def create_view(connection, view_name, view_query, update=True, force=False, mat
             cursor.execute("CREATE TEMPORARY VIEW check_conflict AS SELECT * FROM {0};".format(view_name))
             try:
                 with transaction.atomic():
-                    cursor.execute("CREATE OR REPLACE TEMPORARY VIEW check_conflict AS {0};".format(view_query))
+                    cursor.execute(
+                        "CREATE OR REPLACE TEMPORARY VIEW check_conflict AS {0};".format(view_query.query),
+                        view_query.params,
+                    )
             except psycopg2.ProgrammingError:
                 force_required = True
             finally:
                 cursor.execute("DROP VIEW IF EXISTS check_conflict;")
 
         if materialized:
             cursor.execute("DROP MATERIALIZED VIEW IF EXISTS {0} CASCADE;".format(view_name))
-            cursor.execute("CREATE MATERIALIZED VIEW {0} AS {1};".format(view_name, view_query))
+            cursor.execute(
+                "CREATE MATERIALIZED VIEW {0} AS {1};".format(view_name, view_query.query), view_query.params
+            )
             if index is not None:
                 index_sub_name = "_".join([s.strip() for s in index.split(",")])
                 cursor.execute(
                     "CREATE UNIQUE INDEX {0}_{1}_index ON {0} ({2})".format(view_name, index_sub_name, index)
                 )
             ret = view_exists and "UPDATED" or "CREATED"
         elif not force_required:
-            cursor.execute("CREATE OR REPLACE VIEW {0} AS {1};".format(view_name, view_query))
+            cursor.execute("CREATE OR REPLACE VIEW {0} AS {1};".format(view_name, view_query.query), view_query.params)
             ret = view_exists and "UPDATED" or "CREATED"
         elif force:
             cursor.execute("DROP VIEW IF EXISTS {0} CASCADE;".format(view_name))
-            cursor.execute("CREATE VIEW {0} AS {1};".format(view_name, view_query))
+            cursor.execute("CREATE VIEW {0} AS {1};".format(view_name, view_query.query), view_query.params)
             ret = "FORCED"
         else:
             ret = "FORCE_REQUIRED"
@@ -197,10 +204,15 @@ class BaseManagerMeta:
 
 
 class View(models.Model, metaclass=ViewMeta):
-    """Helper for exposing Postgres views as Django models.
+    """ Helper for exposing Postgres views as Django models.
     """
 
     _deferred = False
+    sql = None
+
+    @classmethod
+    def get_sql(cls):
+        return ViewSQL(cls.sql, None)
 
     class Meta:
         abstract = True

tests/test_project/test_project/viewtest/models.py

@@ -1,4 +1,7 @@
+from datetime import timedelta
+
 from django.db import models
+from django.utils import timezone
 
 from django_pgviews import view
 
@@ -15,6 +18,17 @@ class Superusers(view.View):
     sql = """SELECT * FROM auth_user WHERE is_superuser = TRUE;"""
 
 
+class LatestSuperusers(view.View):  # concept doesn't make much sense, but it will get the job done
+    projection = ["auth.User.*"]
+
+    @classmethod
+    def get_sql(cls):
+        return view.ViewSQL(
+            """SELECT * FROM auth_user WHERE is_superuser = TRUE and date_joined >= %s;""",
+            [timezone.now() - timedelta(days=5)],
+        )
+
+
 class SimpleUser(view.View):
     projection = ["auth.User.username", "auth.User.password"]
     # The row_number() window function is needed so that Django sees some kind

tests/test_project/test_project/viewtest/tests.py

@@ -1,16 +1,21 @@
 """Test Django PGViews.
 """
 from contextlib import closing
+from datetime import timedelta
 
 from django.contrib import auth
+from django.contrib.auth.models import User
 from django.core.management import call_command
 from django.db import connection
 from django.db.models import signals
 from django.dispatch import receiver
 from django.test import TestCase
+from django.utils import timezone
+
 from django_pgviews.signals import view_synced, all_views_synced
 
 from . import models
+from .models import LatestSuperusers
 
 
 @receiver(signals.post_migrate)
@@ -31,7 +36,7 @@ def test_views_have_been_created(self):
             cur.execute("""SELECT COUNT(*) FROM pg_views WHERE viewname LIKE 'viewtest_%';""")
 
             (count,) = cur.fetchone()
-            self.assertEqual(count, 4)
+            self.assertEqual(count, 5)
 
             cur.execute("""SELECT COUNT(*) FROM pg_matviews WHERE matviewname LIKE 'viewtest_%';""")
 
@@ -140,10 +145,18 @@ def on_all_views_synced(sender, **kwargs):
         call_command("sync_pgviews", update=False)
 
         # All views went through syncing
-        self.assertEqual(len(synced_views), 8)
+        self.assertEqual(len(synced_views), 9)
         self.assertEqual(all_views_were_synced[0], True)
         self.assertFalse(expected)
 
+    def test_get_sql(self):
+        User.objects.create(username="old", is_superuser=True, date_joined=timezone.now() - timedelta(days=10))
+        User.objects.create(username="new", is_superuser=True, date_joined=timezone.now() - timedelta(days=1))
+
+        call_command("sync_pgviews", update=False)
+
+        self.assertEqual(LatestSuperusers.objects.count(), 1)
+
 
 class DependantViewTestCase(TestCase):
     def test_sync_depending_views(self):
@@ -171,7 +184,7 @@ def test_sync_depending_views(self):
             cur.execute("""SELECT COUNT(*) FROM pg_views WHERE viewname LIKE 'viewtest_%';""")
 
             (count,) = cur.fetchone()
-            self.assertEqual(count, 4)
+            self.assertEqual(count, 5)
 
             with self.assertRaises(Exception):
                 cur.execute("""SELECT name from viewtest_relatedview;""")
@@ -203,13 +216,10 @@ def test_sync_depending_materialized_views(self):
         call_command("sync_pgviews", "--force")
 
         with closing(connection.cursor()) as cur:
-            cur.execute(
-                """SELECT COUNT(*) FROM pg_views
-                        WHERE viewname LIKE 'viewtest_%';"""
-            )
+            cur.execute("""SELECT COUNT(*) FROM pg_views WHERE viewname LIKE 'viewtest_%';""")
 
             (count,) = cur.fetchone()
-            self.assertEqual(count, 4)
+            self.assertEqual(count, 5)
 
             with self.assertRaises(Exception):
                 cur.execute("""SELECT name from viewtest_dependantmaterializedview;""")