add row counts feature for readabledataset

dlt/common/destination/reference.py

@@ -580,6 +580,10 @@ def __getitem__(self, table: str) -> SupportsReadableRelation: ...
 
     def __getattr__(self, table: str) -> SupportsReadableRelation: ...
 
+    def row_counts(
+        self, *, data_tables: bool = True, dlt_tables: bool = False, table_names: List[str] = None
+    ) -> SupportsReadableRelation: ...
+
 
 class JobClientBase(ABC):
     def __init__(

dlt/destinations/dataset.py

@@ -1,4 +1,4 @@
-from typing import Any, Generator, Optional, Sequence, Union, List
+from typing import Any, Generator, Optional, Sequence, Union, List, Dict
 from dlt.common.json import json
 from copy import deepcopy
 
@@ -300,6 +300,32 @@ def __getattr__(self, table_name: str) -> SupportsReadableRelation:
         """access of table via property notation"""
         return self.table(table_name)
 
+    def row_counts(
+        self, *, data_tables: bool = True, dlt_tables: bool = False, table_names: List[str] = None
+    ) -> SupportsReadableRelation:
+        """Returns a dictionary of table names and their row counts, returns counts of all data tables by default"""
+        """If table_names is provided, only the tables in the list are returned regardless of the data_tables and dlt_tables flags"""
+
+        selected_tables = table_names or []
+        if not selected_tables:
+            if data_tables:
+                selected_tables += self.schema.data_table_names(seen_data_only=True)
+            if dlt_tables:
+                selected_tables += self.schema.dlt_table_names()
+
+        # Build UNION ALL query to get row counts for all selected tables
+        queries = []
+        for table in selected_tables:
+            queries.append(
+                f"SELECT '{table}' as table_name, COUNT(*) as row_count FROM"
+                f" {self.sql_client.make_qualified_table_name(table)}"
+            )
+
+        query = " UNION ALL ".join(queries)
+
+        # Execute query and build result dict
+        return self(query)
+
 
 def dataset(
     destination: TDestinationReferenceArg,

tests/load/test_read_interfaces.py

@@ -203,7 +203,6 @@ def test_dataframe_access(populated_pipeline: Pipeline) -> None:
     if not skip_df_chunk_size_check:
         assert len(df.index) == chunk_size
 
-    # lowercase results for the snowflake case
     assert set(df.columns.values) == set(EXPECTED_COLUMNS)
 
     # iterate all dataframes
@@ -292,6 +291,90 @@ def test_loads_table_access(populated_pipeline: Pipeline) -> None:
     assert len(loads_table.fetchall()) == 1
 
 
+@pytest.mark.no_load
+@pytest.mark.essential
+@pytest.mark.parametrize(
+    "populated_pipeline",
+    configs,
+    indirect=True,
+    ids=lambda x: x.name,
+)
+def test_row_counts(populated_pipeline: Pipeline) -> None:
+    total_records = _total_records(populated_pipeline)
+
+    dataset = populated_pipeline._dataset()
+    # default is all data tables
+    assert set(dataset.row_counts().df().itertuples(index=False, name=None)) == {
+        (
+            "items",
+            total_records,
+        ),
+        (
+            "double_items",
+            total_records,
+        ),
+        (
+            "items__children",
+            total_records * 2,
+        ),
+    }
+    # get only one data table
+    assert set(
+        dataset.row_counts(table_names=["items"]).df().itertuples(index=False, name=None)
+    ) == {
+        (
+            "items",
+            total_records,
+        ),
+    }
+    # get all dlt tables
+    assert set(
+        dataset.row_counts(dlt_tables=True, data_tables=False)
+        .df()
+        .itertuples(index=False, name=None)
+    ) == {
+        (
+            "_dlt_version",
+            1,
+        ),
+        (
+            "_dlt_loads",
+            1,
+        ),
+        (
+            "_dlt_pipeline_state",
+            1,
+        ),
+    }
+    # get them all
+    assert set(dataset.row_counts(dlt_tables=True).df().itertuples(index=False, name=None)) == {
+        (
+            "_dlt_version",
+            1,
+        ),
+        (
+            "_dlt_loads",
+            1,
+        ),
+        (
+            "_dlt_pipeline_state",
+            1,
+        ),
+        (
+            "items",
+            total_records,
+        ),
+        (
+            "double_items",
+            total_records,
+        ),
+        (
+            "items__children",
+            total_records * 2,
+        ),
+    }
+
+
 @pytest.mark.no_load
 @pytest.mark.essential
 @pytest.mark.parametrize(