fix(ingest/profiling): compute sample row count correctly (#10319)

metadata-ingestion/src/datahub/ingestion/source/ge_data_profiler.py

@@ -689,9 +689,28 @@ class _SingleDatasetProfiler(BasicDatasetProfilerBase):
         logger.debug(f"profiling {self.dataset_name}: flushing stage 1 queries")
         self.query_combiner.flush()
 
+        assert profile.rowCount is not None
+        full_row_count = profile.rowCount
+
         if self.config.use_sampling and not self.config.limit:
             self.update_dataset_batch_use_sampling(profile)
 
+        # Note that this row count may be different from the full_row_count if we are using sampling.
+        row_count: int = profile.rowCount
+        if profile.partitionSpec and "SAMPLE" in profile.partitionSpec.partition:
+            # Querying exact row count of sample using `_get_dataset_rows`.
+            # We are not using `self.config.sample_size` directly as the actual row count
+            # in the sample may be different than configured `sample_size`. For BigQuery,
+            # we've even seen 160k rows returned for a sample size of 10k.
+            logger.debug("Recomputing row count for the sample")
+
+            # Note that we can't just call `self._get_dataset_rows(profile)` here because
+            # there's some sort of caching happening that will return the full table row count
+            # instead of the sample row count.
+            row_count = self.dataset.get_row_count(str(self.dataset._table))
+
+            profile.partitionSpec.partition += f" (sample rows {row_count})"
+
         columns_profiling_queue: List[_SingleColumnSpec] = []
         if columns_to_profile:
             for column in all_columns:
@@ -708,16 +727,6 @@ class _SingleDatasetProfiler(BasicDatasetProfilerBase):
         logger.debug(f"profiling {self.dataset_name}: flushing stage 2 queries")
         self.query_combiner.flush()
 
-        assert profile.rowCount is not None
-        row_count: int  # used for null counts calculation
-        if profile.partitionSpec and "SAMPLE" in profile.partitionSpec.partition:
-            # Querying exact row count of sample using `_get_dataset_rows`.
-            # We are not using `self.config.sample_size` directly as actual row count
-            # in sample may be slightly different (more or less) than configured `sample_size`.
-            self._get_dataset_rows(profile)
-
-        row_count = profile.rowCount
-
         for column_spec in columns_profiling_queue:
             column = column_spec.column
             column_profile = column_spec.column_profile
@@ -825,6 +834,10 @@ class _SingleDatasetProfiler(BasicDatasetProfilerBase):
 
         logger.debug(f"profiling {self.dataset_name}: flushing stage 3 queries")
         self.query_combiner.flush()
+
+        # Reset the row count to the original value.
+        profile.rowCount = full_row_count
+
         return profile
 
     def init_profile(self):
@@ -1274,6 +1287,7 @@ def create_bigquery_temp_table(
     try:
         cursor: "BigQueryCursor" = cast("BigQueryCursor", raw_connection.cursor())
         try:
+            logger.debug(f"Creating temporary table for {table_pretty_name}: {bq_sql}")
             cursor.execute(bq_sql)
         except Exception as e:
             if not instance.config.catch_exceptions:

metadata-ingestion/src/datahub/ingestion/source/sql/sql_generic_profiler.py

@@ -159,7 +159,7 @@ class GenericProfiler:
             rows_count=table.rows_count,
         ):
             logger.debug(
-                f"Dataset {dataset_name} was not eliagable for profiling due to last_altered, size in bytes or count of rows limit"
+                f"Dataset {dataset_name} was not eligible for profiling due to last_altered, size in bytes or count of rows limit"
             )
             # Profile only table level if dataset is filtered from profiling
             # due to size limits alone