fix: Use boot_val for is_default check on lock_timeout

When pgwatch sets lock_timeout during collection, source becomes
'session', causing is_default to incorrectly report non-default.
Now we compare reset_val with boot_val to determine the true default
status for lock_timeout.

Author: claude

config/pgwatch-prometheus/metrics.yml

@@ -377,7 +377,8 @@ metrics:
           category as tag_category,
           vartype as tag_vartype,
           case when (case when name = 'lock_timeout' then reset_val else setting end) ~ '^-?[0-9]+$' then (case when name = 'lock_timeout' then reset_val else setting end)::bigint else null end as numeric_value,
-          case when source <> 'default' then 0 else 1 end as is_default,
+          -- For lock_timeout, compare reset_val with boot_val since source becomes 'session' during collection
+          case when name = 'lock_timeout' then (case when reset_val = boot_val then 1 else 0 end) else (case when source <> 'default' then 0 else 1 end) end as is_default,
           1 as configured
         from pg_settings
     gauges:

tests/settings/test_settings_metric.py

@@ -110,6 +110,27 @@ def test_settings_metric_numeric_value_uses_correct_source_for_lock_timeout(metr
         f"CASE expression for lock_timeout should appear at least twice (for tag_setting_value and numeric_value), found {occurrences}"
 
 
+@pytest.mark.unit
+def test_settings_metric_is_default_uses_boot_val_for_lock_timeout(metrics_config: dict) -> None:
+    """
+    Test that is_default compares reset_val with boot_val for lock_timeout.
+
+    When pgwatch sets lock_timeout during collection, the source becomes 'session',
+    which would incorrectly report is_default=0. Instead, we should compare
+    reset_val with boot_val to determine if the configured value is the default.
+
+    See: https://gitlab.com/postgres-ai/postgres_ai/-/issues/61
+    """
+    sql = metrics_config["metrics"]["settings"]["sqls"][11]
+
+    # Verify is_default uses boot_val comparison for lock_timeout
+    assert "boot_val" in sql, "SQL should reference boot_val column for is_default comparison"
+
+    # Check for the specific pattern that handles lock_timeout specially
+    assert "case when name = 'lock_timeout' then" in sql and "boot_val" in sql, \
+        "SQL should use special handling for lock_timeout in is_default calculation"
+
+
 @pytest.mark.integration
 @pytest.mark.requires_postgres
 def test_settings_metric_lock_timeout_returns_actual_value() -> None: