chore: add exec_seconds attribute to ExecutionMetrics (#1104)

* chore: score query count assertion fix.

* chore: add exec_seconds attribute to ExecutionMetrics

* update naming

* update logic.

* update logic.

* update logic.

* update logic.

Author: Genesis929

bigframes/session/metrics.py

@@ -29,48 +29,47 @@ class ExecutionMetrics:
     execution_count: int = 0
     slot_millis: int = 0
     bytes_processed: int = 0
+    execution_secs: float = 0
 
     def count_job_stats(self, query_job: bq_job.QueryJob):
         stats = get_performance_stats(query_job)
         if stats is not None:
-            bytes_processed, slot_millis, exec_seconds = stats
+            bytes_processed, slot_millis, execution_secs = stats
             self.execution_count += 1
             self.bytes_processed += bytes_processed
             self.slot_millis += slot_millis
+            self.execution_secs += execution_secs
             if LOGGING_NAME_ENV_VAR in os.environ:
                 # when running notebooks via pytest nbmake
-                write_stats_to_disk(bytes_processed, slot_millis, exec_seconds)
+                write_stats_to_disk(bytes_processed, slot_millis, execution_secs)
 
 
 def get_performance_stats(
     query_job: bigquery.QueryJob,
-) -> Optional[Tuple[int, int, Optional[float]]]:
+) -> Optional[Tuple[int, int, float]]:
     """Parse the query job for performance stats.
 
     Return None if the stats do not reflect real work done in bigquery.
     """
+
+    if (
+        query_job.configuration.dry_run
+        or query_job.created is None
+        or query_job.ended is None
+    ):
+        return None
+
     bytes_processed = query_job.total_bytes_processed
     if not isinstance(bytes_processed, int):
         return None  # filter out mocks
-    if query_job.configuration.dry_run:
-        # dry run stats are just predictions of the real run
-        bytes_processed = 0
 
     slot_millis = query_job.slot_millis
     if not isinstance(slot_millis, int):
         return None  # filter out mocks
 
-    if query_job.configuration.dry_run:
-        # dry run stats are just predictions of the real run
-        slot_millis = 0
-
-    exec_seconds = (
-        (query_job.ended - query_job.created).total_seconds()
-        if query_job.created is not None and query_job.ended is not None
-        else None
-    )
+    execution_secs = (query_job.ended - query_job.created).total_seconds()
 
-    return bytes_processed, slot_millis, exec_seconds
+    return bytes_processed, slot_millis, execution_secs
 
 
 def write_stats_to_disk(