fix(experiments): Hackily apply timestamp to ASOF LEFT JOIN (#26852)

posthog/hogql_queries/experiments/test/test_experiment_trends_query_runner.py

@@ -36,6 +36,7 @@
 from posthog.warehouse.models.credential import DataWarehouseCredential
 from posthog.warehouse.models.join import DataWarehouseJoin
 from posthog.warehouse.models.table import DataWarehouseTable
+from posthog.hogql.query import execute_hogql_query
 
 TEST_BUCKET = "test_storage_bucket-posthog.hogql.datawarehouse.trendquery" + XDIST_SUFFIX
 
@@ -693,6 +694,87 @@ def test_query_runner_with_data_warehouse_series_avg_amount(self):
             [0.0, 50.0, 125.0, 125.0, 125.0, 205.0, 205.0, 205.0, 205.0, 205.0],
         )
 
+    def test_query_runner_with_data_warehouse_series_expected_query(self):
+        table_name = self.create_data_warehouse_table_with_payments()
+
+        feature_flag = self.create_feature_flag()
+        experiment = self.create_experiment(
+            feature_flag=feature_flag,
+            start_date=datetime(2023, 1, 1),
+            end_date=datetime(2023, 1, 10),
+        )
+
+        feature_flag_property = f"$feature/{feature_flag.key}"
+
+        count_query = TrendsQuery(
+            series=[
+                DataWarehouseNode(
+                    id=table_name,
+                    distinct_id_field="dw_distinct_id",
+                    id_field="id",
+                    table_name=table_name,
+                    timestamp_field="dw_timestamp",
+                    math="total",
+                )
+            ]
+        )
+        exposure_query = TrendsQuery(series=[EventsNode(event="$feature_flag_called")])
+
+        experiment_query = ExperimentTrendsQuery(
+            experiment_id=experiment.id,
+            kind="ExperimentTrendsQuery",
+            count_query=count_query,
+            exposure_query=exposure_query,
+        )
+
+        experiment.metrics = [{"type": "primary", "query": experiment_query.model_dump()}]
+        experiment.save()
+
+        # Populate exposure events
+        for variant, count in [("control", 7), ("test", 9)]:
+            for i in range(count):
+                _create_event(
+                    team=self.team,
+                    event="$feature_flag_called",
+                    distinct_id=f"user_{variant}_{i}",
+                    properties={feature_flag_property: variant},
+                    timestamp=datetime(2023, 1, i + 1),
+                )
+
+        flush_persons_and_events()
+
+        query_runner = ExperimentTrendsQueryRunner(
+            query=ExperimentTrendsQuery(**experiment.metrics[0]["query"]), team=self.team
+        )
+        with freeze_time("2023-01-07"):
+            # Build and execute the query to get the ClickHouse SQL
+            queries = query_runner.count_query_runner.to_queries()
+            response = execute_hogql_query(
+                query_type="TrendsQuery",
+                query=queries[0],
+                team=query_runner.count_query_runner.team,
+                modifiers=query_runner.count_query_runner.modifiers,
+                limit_context=query_runner.count_query_runner.limit_context,
+            )
+
+            # Assert the expected join condition in the clickhouse SQL
+            expected_join_condition = f"and(equals(events.team_id, {query_runner.count_query_runner.team.id}), equals(event, %(hogql_val_7)s), greaterOrEquals(timestamp, assumeNotNull(parseDateTime64BestEffortOrNull(%(hogql_val_8)s, 6, %(hogql_val_9)s))), lessOrEquals(timestamp, assumeNotNull(parseDateTime64BestEffortOrNull(%(hogql_val_10)s, 6, %(hogql_val_11)s))))) AS e__events ON"
+            self.assertIn(expected_join_condition, str(response.clickhouse))
+
+            result = query_runner.calculate()
+
+        trend_result = cast(ExperimentTrendsQueryResponse, result)
+
+        self.assertEqual(len(result.variants), 2)
+
+        control_result = next(variant for variant in trend_result.variants if variant.key == "control")
+        test_result = next(variant for variant in trend_result.variants if variant.key == "test")
+
+        self.assertEqual(control_result.count, 1)
+        self.assertEqual(test_result.count, 3)
+        self.assertEqual(control_result.absolute_exposure, 7)
+        self.assertEqual(test_result.absolute_exposure, 9)
+
     def test_query_runner_with_invalid_data_warehouse_table_name(self):
         # parquet file isn't created, so we'll get an error
         table_name = "invalid_table_name"

posthog/warehouse/models/join.py

@@ -113,6 +113,26 @@ def _join_function_for_experiments(
             if not timestamp_key:
                 raise ResolutionError("experiments_timestamp_key is not set for this join")
 
+            whereExpr: list[ast.Expr] = [
+                ast.CompareOperation(
+                    op=ast.CompareOperationOp.Eq,
+                    left=ast.Field(chain=["event"]),
+                    right=ast.Constant(value="$feature_flag_called"),
+                )
+            ]
+            # :HACK: We need to pull the timestamp gt/lt values from node.where.exprs[0] because
+            # we can't reference the parent data warehouse table in the where clause.
+            if node.where and hasattr(node.where, "exprs"):
+                for expr in node.where.exprs:
+                    if isinstance(expr, ast.CompareOperation):
+                        if expr.op == ast.CompareOperationOp.GtEq or expr.op == ast.CompareOperationOp.LtEq:
+                            if isinstance(expr.left, ast.Alias) and expr.left.expr.to_hogql() == timestamp_key:
+                                whereExpr.append(
+                                    ast.CompareOperation(
+                                        op=expr.op, left=ast.Field(chain=["timestamp"]), right=expr.right
+                                    )
+                                )
+
             return ast.JoinExpr(
                 table=ast.SelectQuery(
                     select=[
@@ -128,11 +148,7 @@ def _join_function_for_experiments(
                         }.items()
                     ],
                     select_from=ast.JoinExpr(table=ast.Field(chain=["events"])),
-                    where=ast.CompareOperation(
-                        op=ast.CompareOperationOp.Eq,
-                        left=ast.Field(chain=["event"]),
-                        right=ast.Constant(value="$feature_flag_called"),
-                    ),
+                    where=ast.And(exprs=whereExpr),
                 ),
                 # ASOF JOIN finds the most recent matching event that occurred at or before each data warehouse timestamp.
                 #