fix(discover): Fix has:measurements.* queries (#78627)

Fixes SENTRY-3DB9

We're seeing Snuba errors for comparisons of a numeric value to a
string. e.g.,

```sql
`measurements.frames_frozen_rate` != ''
```

Measurements are numeric, so this errors out. This comparison is created
for queries like `has:measurements.frozen_frame_rate`. That measurement
is "synthetic", it's a function that divides two other measurements. It
returns a numeric value, so comparison to string fails. The query
builder's current logic doesn't account for measurement _functions_
(i.e., plain measurements like `measurements.lcp` still work), and
creates the comparison incorrectly.

The fix is to check for measurements, and return early with a basic
check for null.

Author: gggritso

src/sentry/search/events/builder/base.py

@@ -1309,6 +1309,11 @@ def default_filter_converter(
         if search_filter.operator in ("=", "!=") and search_filter.value.value == "":
             if is_tag or is_attr or is_context or name in self.config.non_nullable_keys:
                 return Condition(lhs, Op(search_filter.operator), value)
+            elif is_measurement(name):
+                # Measurements can be a `Column` (e.g., `"lcp"`) or a `Function` (e.g., `"frames_frozen_rate"`). In either cause, since they are nullable, return a simple null check
+                return Condition(
+                    Function("isNull", [lhs]), Op.EQ, 1 if search_filter.operator == "=" else 0
+                )
             elif isinstance(lhs, Column):
                 # If not a tag, we can just check that the column is null.
                 return Condition(Function("isNull", [lhs]), Op(search_filter.operator), 1)

tests/sentry/search/events/builder/test_discover.py

@@ -475,6 +475,51 @@ def test_count_if_with_tags(self):
             ],
         )
 
+    def test_not_empty_measurement(self):
+        query = DiscoverQueryBuilder(
+            Dataset.Discover,
+            self.params,
+            query="has:measurements.lcp",
+        )
+
+        lcp = Column("measurements[lcp]")
+
+        self.assertCountEqual(
+            query.where,
+            [
+                Condition(Function("isNull", [lcp]), Op.EQ, 0),
+                *self.default_conditions,
+            ],
+        )
+
+    def test_not_empty_function_measurement(self):
+        query = DiscoverQueryBuilder(
+            Dataset.Discover,
+            self.params,
+            query="has:measurements.frames_frozen_rate",
+        )
+
+        frames_total = Column("measurements[frames_total]")
+        frames_frozen = Column("measurements[frames_frozen]")
+
+        frames_frozen_rate = Function(
+            "if",
+            [
+                Function("greater", [frames_total, 0]),
+                Function("divide", [frames_frozen, frames_total]),
+                None,
+            ],
+            alias="measurements.frames_frozen_rate",
+        )
+
+        self.assertCountEqual(
+            query.where,
+            [
+                Condition(Function("isNull", [frames_frozen_rate]), Op.EQ, 0),
+                *self.default_conditions,
+            ],
+        )
+
     def test_array_join(self):
         query = DiscoverQueryBuilder(
             Dataset.Discover,