Auto-wrap ratio metric denominators in NULLIF

datajunction-clients/python/tests/examples.py

@@ -1256,7 +1256,7 @@
     "JOINdefault_repair_ordert2ONt1.repair_order_id=t2.repair_order_idLEFTOUTERJOIN"
     "default_hard_hatt3ONt2.hard_hat_id=t3.hard_hat_idGROUPBYt3.state)SELECT"
     "repair_order_details_0.stateASstate,\tSUM(repair_order_details_0.price_sum_252381cf)"
-    "/SUM(repair_order_details_0.price_count_252381cf)ASavg_repair_priceFROM"
+    "/NULLIF(SUM(repair_order_details_0.price_count_252381cf),0)ASavg_repair_priceFROM"
     "repair_order_details_0GROUPBYrepair_order_details_0.state": QueryWithResults(
         **{
             "id": "bd98d6be-e2d2-413e-94c7-96d9411ddee2",
@@ -1399,7 +1399,7 @@
     "LEFTOUTERJOINdefault_repair_ordert2ONt1.repair_order_id=t2.repair_order_id"
     "LEFTOUTERJOINdefault_hard_hatt3ONt2.hard_hat_id=t3.hard_hat_idGROUPBYt3.city)"
     "SELECTCOALESCE(repair_order_details_0.city)AScity,\tSUM(repair_order_details_0."
-    "price_sum_252381cf)/SUM(repair_order_details_0.price_count_252381cf)AS"
+    "price_sum_252381cf)/NULLIF(SUM(repair_order_details_0.price_count_252381cf),0)AS"
     "avg_repair_priceFROMrepair_order_details_0GROUPBYrepair_order_details_0.city": QueryWithResults(
         id="v3-avg-repair-price-city",
         submitted_query="...",
@@ -1437,7 +1437,7 @@
     "LEFTOUTERJOINdefault_repair_ordert2ONt1.repair_order_id=t2.repair_order_id"
     "LEFTOUTERJOINdefault_hard_hatt3ONt2.hard_hat_id=t3.hard_hat_idGROUPBYt3.city)"
     "SELECTrepair_order_details_0.cityAScity,\tSUM(repair_order_details_0."
-    "price_sum_252381cf)/SUM(repair_order_details_0.price_count_252381cf)AS"
+    "price_sum_252381cf)/NULLIF(SUM(repair_order_details_0.price_count_252381cf),0)AS"
     "avg_repair_priceFROMrepair_order_details_0GROUPBYrepair_order_details_0.city": QueryWithResults(
         id="v3-avg-repair-price-city",
         submitted_query="...",
@@ -1465,7 +1465,7 @@
     "LEFTOUTERJOINdefault_repair_ordert2ONt1.repair_order_id=t2.repair_order_id"
     "LEFTOUTERJOINdefault_hard_hatt3ONt2.hard_hat_id=t3.hard_hat_idGROUPBYt3.state)"
     "SELECTCOALESCE(repair_order_details_0.state)ASstate,\tSUM(repair_order_details_0."
-    "price_sum_252381cf)/SUM(repair_order_details_0.price_count_252381cf)AS"
+    "price_sum_252381cf)/NULLIF(SUM(repair_order_details_0.price_count_252381cf),0)AS"
     "avg_repair_priceFROMrepair_order_details_0GROUPBYrepair_order_details_0.state": QueryWithResults(
         id="v3-avg-repair-price-state-no-data",
         submitted_query="...",
@@ -1481,7 +1481,7 @@
     "LEFTOUTERJOINdefault_repair_ordert2ONt1.repair_order_id=t2.repair_order_id"
     "LEFTOUTERJOINdefault_hard_hatt3ONt2.hard_hat_id=t3.hard_hat_idGROUPBYt3.state)"
     "SELECTrepair_order_details_0.stateASstate,\tSUM(repair_order_details_0."
-    "price_sum_252381cf)/SUM(repair_order_details_0.price_count_252381cf)AS"
+    "price_sum_252381cf)/NULLIF(SUM(repair_order_details_0.price_count_252381cf),0)AS"
     "avg_repair_priceFROMrepair_order_details_0GROUPBYrepair_order_details_0.state": QueryWithResults(
         id="v3-avg-repair-price-state-no-data-no-coalesce",
         submitted_query="...",
@@ -1498,7 +1498,7 @@
     "LEFTOUTERJOINdefault_repair_ordert2ONt1.repair_order_id=t2.repair_order_id"
     "LEFTOUTERJOINdefault_hard_hatt3ONt2.hard_hat_id=t3.hard_hat_idGROUPBYt3.city)"
     "SELECTrepair_order_details_0.cityAScity,\tSUM(repair_order_details_0."
-    "price_sum_252381cf)/SUM(repair_order_details_0.price_count_252381cf)AS"
+    "price_sum_252381cf)/NULLIF(SUM(repair_order_details_0.price_count_252381cf),0)AS"
     "avg_repair_priceFROMrepair_order_details_0GROUPBYrepair_order_details_0.city": QueryWithResults(
         id="v3-avg-repair-price-city-with-join-key",
         submitted_query="...",
@@ -1526,7 +1526,7 @@
     "LEFTOUTERJOINdefault_repair_ordert2ONt1.repair_order_id=t2.repair_order_id"
     "LEFTOUTERJOINdefault_hard_hatt3ONt2.hard_hat_id=t3.hard_hat_idGROUPBYt3.state)"
     "SELECTrepair_order_details_0.stateASstate,\tSUM(repair_order_details_0."
-    "price_sum_252381cf)/SUM(repair_order_details_0.price_count_252381cf)AS"
+    "price_sum_252381cf)/NULLIF(SUM(repair_order_details_0.price_count_252381cf),0)AS"
     "avg_repair_priceFROMrepair_order_details_0GROUPBYrepair_order_details_0.state": QueryWithResults(
         id="v3-avg-repair-price-state-no-data-with-join-key",
         submitted_query="...",

datajunction-server/datajunction_server/construction/build_v3/cte.py

@@ -23,6 +23,7 @@
 from datajunction_server.construction.build_v3.utils import get_cte_name
 from datajunction_server.database.node import Node
 from datajunction_server.models.node_type import NodeType
+from datajunction_server.sql.decompose import wrap_divisions_in_nullif
 from datajunction_server.sql.parsing import ast
 from datajunction_server.utils import SEPARATOR
 
@@ -1593,4 +1594,8 @@ def process_metric_combiner_expression(
             partition_cte_alias=cte_alias,
         )
 
+    # Wrap denominators so user-authored ratio metrics don't blow up on
+    # zero (NaN/Infinity/error → NULL).  Idempotent.
+    wrap_divisions_in_nullif(expr_ast)
+
     return expr_ast

datajunction-server/datajunction_server/construction/build_v3/metrics.py

@@ -10,7 +10,7 @@
 import logging
 from copy import deepcopy
 from dataclasses import dataclass
-from typing import Any, Optional
+from typing import Any, Optional, cast
 
 from datajunction_server.construction.build_v3.cte import (
     build_alias_to_dimension_node,
@@ -50,6 +50,7 @@
 from datajunction_server.errors import DJInvalidInputException
 from datajunction_server.models.decompose import Aggregability
 from datajunction_server.models.node_type import NodeType
+from datajunction_server.sql.decompose import wrap_divisions_in_nullif
 from datajunction_server.sql.parsing import ast
 
 logger = logging.getLogger(__name__)
@@ -686,6 +687,10 @@ def build_intermediate_metric_expr(
                 # The dependency hasn't been built, so defer this metric
                 return None  # pragma: no cover
 
+    # Intermediate derived metrics like avg_order_value =
+    # total_revenue / order_count inline raw aggregations on both
+    # sides — wrap denominators to avoid NaN/Infinity/error on 0.
+    wrap_divisions_in_nullif(cast(ast.Expression, expr_ast))
     return expr_ast  # type: ignore
 
 

datajunction-server/datajunction_server/internal/materializations.py

@@ -428,8 +428,14 @@ def decompose_expression(
                     args=[ast.Column(name=numerator_measure_name)],
                 ),
                 right=ast.Function(
-                    ast.Name("count"),
-                    args=[ast.Column(name=denominator_measure_name)],
+                    ast.Name("NULLIF"),
+                    args=[
+                        ast.Function(
+                            ast.Name("count"),
+                            args=[ast.Column(name=denominator_measure_name)],
+                        ),
+                        ast.Number(value=0),
+                    ],
                 ),
                 op=ast.BinaryOpKind.Divide,
             )
@@ -455,6 +461,14 @@ def decompose_expression(
         if expr.op in acceptable_binary_ops:  # pragma: no cover
             measures_combiner_left, measures_left = decompose_expression(expr.left)
             measures_combiner_right, measures_right = decompose_expression(expr.right)
+            if expr.op == ast.BinaryOpKind.Divide and not (
+                isinstance(measures_combiner_right, ast.Function)
+                and measures_combiner_right.alias_or_name.name.lower() == "nullif"
+            ):
+                measures_combiner_right = ast.Function(
+                    ast.Name("NULLIF"),
+                    args=[measures_combiner_right, ast.Number(value=0)],
+                )
             combiner = ast.BinaryOp(
                 left=measures_combiner_left,
                 right=measures_combiner_right,

datajunction-server/datajunction_server/sql/decompose.py

@@ -34,6 +34,45 @@ def make_func(name: str, *args: ast.Expression | str) -> ast.Function:
     )
 
 
+def safe_denominator(expr: ast.Expression) -> ast.Expression:
+    """Wrap expr in NULLIF(expr, 0) to make it safe as a divisor.
+
+    Idempotent: if expr is already NULLIF(_, 0) or a numeric literal,
+    returns it unchanged.  Caller passes the RHS of a Divide.
+    """
+    # Numeric literals: x / 100 doesn't need wrapping.
+    if isinstance(expr, ast.Number):
+        return expr
+    # Already wrapped.
+    if (
+        isinstance(expr, ast.Function)
+        and expr.name.name.upper() == "NULLIF"
+        and len(expr.args) == 2
+        and isinstance(expr.args[1], ast.Number)
+        and expr.args[1].value == 0
+    ):
+        return expr
+    return ast.Function(
+        ast.Name("NULLIF"),
+        args=[expr, ast.Number(value=0)],
+    )
+
+
+def wrap_divisions_in_nullif(expr: ast.Expression) -> ast.Expression:
+    """Walk expr and wrap the RHS of every Divide BinaryOp in NULLIF(_, 0)
+    so division-by-zero produces NULL instead of NaN/Infinity/error.
+
+    Mutates and returns expr.  Idempotent via :func:`safe_denominator`.
+    """
+    for node in expr.find_all(ast.BinaryOp):
+        if node.op != ast.BinaryOpKind.Divide:
+            continue
+        wrapped = safe_denominator(node.right)
+        if wrapped is not node.right:
+            node.right = wrapped
+    return expr
+
+
 # =============================================================================
 # Decomposition Framework
 # =============================================================================
@@ -999,6 +1038,15 @@ def _extract_base(
                             components_tracker.add(comp.name)
                             components.append(comp)
 
+            # Wrap user-authored divisions in the outer expression too.
+            # _decompose only wraps the small combiners it builds for AVG /
+            # variance / stddev / covariance; the user's top-level
+            # expression (e.g. CAST(SUM(...)) / COUNT(*)) is unchanged
+            # after sub-aggregation replacements and would otherwise emit
+            # bare divisions.
+            for proj in query_ast.select.projection:
+                wrap_divisions_in_nullif(cast(ast.Expression, proj))
+
         return components, query_ast
 
     def _substitute_metric_references(
@@ -1080,6 +1128,11 @@ def _decompose(
             )
         else:
             combiner_ast = decomposition.combine(components)
+            # Decomposed AVG / variance / stddev / covariance all build
+            # SUM(...) / SUM(count)-style combiners where the denominator
+            # can legitimately be 0.  Wrap to produce NULL rather than
+            # NaN/Infinity/error.
+            combiner_ast = wrap_divisions_in_nullif(combiner_ast)
 
         return DecompositionResult(components, combiner_ast)
 

datajunction-server/tests/api/cubes_test.py

@@ -947,9 +947,9 @@ async def test_create_cube(
   COALESCE(repair_order_details_0.company_name, repair_orders_fact_0.company_name) AS company_name,
   COALESCE(repair_order_details_0.local_region, repair_orders_fact_0.local_region) AS local_region,
   COALESCE(repair_order_details_0.hire_date, repair_orders_fact_0.hire_date) AS hire_date,
-  CAST(SUM(repair_orders_fact_0.discount_sum_30b84e6c) AS DOUBLE) / SUM(repair_orders_fact_0.count_c8e42e74) AS discounted_orders_rate,
+  CAST(SUM(repair_orders_fact_0.discount_sum_30b84e6c) AS DOUBLE) / NULLIF(SUM(repair_orders_fact_0.count_c8e42e74), 0) AS discounted_orders_rate,
   SUM(repair_orders_fact_0.repair_order_id_count_bd241964) AS num_repair_orders,
-  SUM(repair_orders_fact_0.price_sum_935e7117) / SUM(repair_orders_fact_0.price_count_935e7117) AS avg_repair_price,
+  SUM(repair_orders_fact_0.price_sum_935e7117) / NULLIF(SUM(repair_orders_fact_0.price_count_935e7117), 0) AS avg_repair_price,
   SUM(repair_orders_fact_0.total_repair_cost_sum_67874507) AS total_repair_cost,
   SUM(repair_orders_fact_0.price_discount_sum_e4ba5456) AS total_repair_order_discounts,
   SUM(repair_order_details_0.price_sum_252381cf) + SUM(repair_order_details_0.price_sum_252381cf) AS double_total_repair_cost
@@ -1082,9 +1082,9 @@ async def test_cube_filters_merged_with_request_filters(
           COALESCE(repair_order_details_0.company_name, repair_orders_fact_0.company_name) AS company_name,
           COALESCE(repair_order_details_0.local_region, repair_orders_fact_0.local_region) AS local_region,
           COALESCE(repair_order_details_0.hire_date, repair_orders_fact_0.hire_date) AS hire_date,
-          CAST(SUM(repair_orders_fact_0.discount_sum_30b84e6c) AS DOUBLE) / SUM(repair_orders_fact_0.count_c8e42e74) AS discounted_orders_rate,
+          CAST(SUM(repair_orders_fact_0.discount_sum_30b84e6c) AS DOUBLE) / NULLIF(SUM(repair_orders_fact_0.count_c8e42e74), 0) AS discounted_orders_rate,
           SUM(repair_orders_fact_0.repair_order_id_count_bd241964) AS num_repair_orders,
-          SUM(repair_orders_fact_0.price_sum_935e7117) / SUM(repair_orders_fact_0.price_count_935e7117) AS avg_repair_price,
+          SUM(repair_orders_fact_0.price_sum_935e7117) / NULLIF(SUM(repair_orders_fact_0.price_count_935e7117), 0) AS avg_repair_price,
           SUM(repair_orders_fact_0.total_repair_cost_sum_67874507) AS total_repair_cost,
           SUM(repair_orders_fact_0.price_discount_sum_e4ba5456) AS total_repair_order_discounts,
           SUM(repair_order_details_0.price_sum_252381cf) + SUM(repair_order_details_0.price_sum_252381cf) AS double_total_repair_cost
@@ -1163,7 +1163,7 @@ async def test_cube_filters_applied_in_v3_sql_via_cube_param(
         SELECT repair_orders_fact_0.state AS state,
           repair_orders_fact_0.company_name AS company_name,
           SUM(repair_orders_fact_0.repair_order_id_count_bd241964) AS num_repair_orders,
-          SUM(repair_orders_fact_0.price_sum_935e7117) / SUM(repair_orders_fact_0.price_count_935e7117) AS avg_repair_price,
+          SUM(repair_orders_fact_0.price_sum_935e7117) / NULLIF(SUM(repair_orders_fact_0.price_count_935e7117), 0) AS avg_repair_price,
           SUM(repair_orders_fact_0.total_repair_cost_sum_67874507) AS total_repair_cost
         FROM repair_orders_fact_0
         WHERE repair_orders_fact_0.state = 'AZ'
@@ -1247,7 +1247,7 @@ async def test_cube_filters_applied_in_v3_sql_via_cube_param(
         SELECT repair_orders_fact_0.state AS state,
           repair_orders_fact_0.company_name AS company_name,
           SUM(repair_orders_fact_0.repair_order_id_count_bd241964) AS num_repair_orders,
-          SUM(repair_orders_fact_0.price_sum_935e7117) / SUM(repair_orders_fact_0.price_count_935e7117) AS avg_repair_price,
+          SUM(repair_orders_fact_0.price_sum_935e7117) / NULLIF(SUM(repair_orders_fact_0.price_count_935e7117), 0) AS avg_repair_price,
           SUM(repair_orders_fact_0.total_repair_cost_sum_67874507) AS total_repair_cost
         FROM repair_orders_fact_0
         GROUP BY repair_orders_fact_0.state, repair_orders_fact_0.company_name
@@ -1296,7 +1296,7 @@ async def test_cube_filters_applied_in_v3_sql_via_cube_param(
         SELECT repair_orders_fact_0.state AS state,
           repair_orders_fact_0.company_name AS company_name,
           SUM(repair_orders_fact_0.repair_order_id_count_bd241964) AS num_repair_orders,
-          SUM(repair_orders_fact_0.price_sum_935e7117) / SUM(repair_orders_fact_0.price_count_935e7117) AS avg_repair_price,
+          SUM(repair_orders_fact_0.price_sum_935e7117) / NULLIF(SUM(repair_orders_fact_0.price_count_935e7117), 0) AS avg_repair_price,
           SUM(repair_orders_fact_0.total_repair_cost_sum_67874507) AS total_repair_cost
         FROM repair_orders_fact_0
         WHERE repair_orders_fact_0.state = 'AZ' AND repair_orders_fact_0.company_name = 'Potts LLC'
@@ -1398,9 +1398,9 @@ async def test_cube_only_no_metrics_no_dims(client_with_repairs_cube: AsyncClien
           COALESCE(repair_order_details_0.company_name, repair_orders_fact_0.company_name) AS company_name,
           COALESCE(repair_order_details_0.local_region, repair_orders_fact_0.local_region) AS local_region,
           COALESCE(repair_order_details_0.hire_date, repair_orders_fact_0.hire_date) AS hire_date,
-          CAST(SUM(repair_orders_fact_0.discount_sum_30b84e6c) AS DOUBLE) / SUM(repair_orders_fact_0.count_c8e42e74) AS discounted_orders_rate,
+          CAST(SUM(repair_orders_fact_0.discount_sum_30b84e6c) AS DOUBLE) / NULLIF(SUM(repair_orders_fact_0.count_c8e42e74), 0) AS discounted_orders_rate,
           SUM(repair_orders_fact_0.repair_order_id_count_bd241964) AS num_repair_orders,
-          SUM(repair_orders_fact_0.price_sum_935e7117) / SUM(repair_orders_fact_0.price_count_935e7117) AS avg_repair_price,
+          SUM(repair_orders_fact_0.price_sum_935e7117) / NULLIF(SUM(repair_orders_fact_0.price_count_935e7117), 0) AS avg_repair_price,
           SUM(repair_orders_fact_0.total_repair_cost_sum_67874507) AS total_repair_cost,
           SUM(repair_orders_fact_0.price_discount_sum_e4ba5456) AS total_repair_order_discounts,
           SUM(repair_order_details_0.price_sum_252381cf) + SUM(repair_order_details_0.price_sum_252381cf) AS double_total_repair_cost
@@ -3000,10 +3000,10 @@ async def test_cube_materialization_metadata(
     assert results["metrics"] == [
         {
             "derived_expression": "SELECT CAST(SUM(discount_sum_30b84e6c) AS DOUBLE) / "
-            "SUM(count_c8e42e74) AS default_DOT_discounted_orders_rate FROM "
+            "NULLIF(SUM(count_c8e42e74), 0) AS default_DOT_discounted_orders_rate FROM "
             "default.repair_orders_fact",
             "metric_expression": "CAST(SUM(discount_sum_30b84e6c) AS DOUBLE) / "
-            "SUM(count_c8e42e74)",
+            "NULLIF(SUM(count_c8e42e74), 0)",
             "metric": {
                 "name": "default.discounted_orders_rate",
                 "version": mock.ANY,
@@ -3049,9 +3049,9 @@ async def test_cube_materialization_metadata(
             ],
         },
         {
-            "derived_expression": "SELECT SUM(price_sum_935e7117) / SUM(price_count_935e7117) FROM "
+            "derived_expression": "SELECT SUM(price_sum_935e7117) / NULLIF(SUM(price_count_935e7117), 0) FROM "
             "default.repair_orders_fact",
-            "metric_expression": "SUM(price_sum_935e7117) / SUM(price_count_935e7117)",
+            "metric_expression": "SUM(price_sum_935e7117) / NULLIF(SUM(price_count_935e7117), 0)",
             "metric": {
                 "name": "default.avg_repair_price",
                 "version": mock.ANY,

datajunction-server/tests/api/deployments_test.py

@@ -1064,8 +1064,8 @@ def default_regional_repair_efficiency():
                 "Total Repair Amount in Region" is the total amount spent on repairs in a given region.
                 "Total Repair Amount Nationwide" is the total amount spent on all repairs nationwide.""",
         query="""SELECT
-    (SUM(rm.completed_repairs) * 1.0 / SUM(rm.total_repairs_dispatched)) *
-    (SUM(rm.total_amount_in_region) * 1.0 / SUM(na.total_amount_nationwide)) * 100
+    (SUM(rm.completed_repairs) * 1.0 / NULLIF(SUM(rm.total_repairs_dispatched), 0)) *
+    (SUM(rm.total_amount_in_region) * 1.0 / NULLIF(SUM(na.total_amount_nationwide), 0)) * 100
 FROM
     ${prefix}default.regional_level_agg rm
 CROSS JOIN

datajunction-server/tests/api/djql_test.py

@@ -483,7 +483,7 @@ async def test_get_djsql_with_orderby_and_limit(
         )
         SELECT
             repair_orders_fact_0.country AS country,
-            SUM(repair_orders_fact_0.price_sum_HASH) / SUM(repair_orders_fact_0.price_count_HASH) AS avg_repair_price
+            SUM(repair_orders_fact_0.price_sum_HASH) / NULLIF(SUM(repair_orders_fact_0.price_count_HASH), 0) AS avg_repair_price
         FROM repair_orders_fact_0
         GROUP BY repair_orders_fact_0.country
         ORDER BY country DESC