Add support of SAMPLE ClickHouse clause

pypika/dialects.py

@@ -781,6 +781,16 @@ def drop_view(self, view: str) -> "ClickHouseDropQueryBuilder":
 class ClickHouseQueryBuilder(QueryBuilder):
  QUERY_CLS = ClickHouseQuery
 
+ def __init__(self, **kwargs) -> None:
+ super().__init__(**kwargs)
+ self._sample = None
+ self._sample_offset = None
+
+ @builder
+ def sample(self, sample: int, offset: Optional[int] = None) -> "ClickHouseQueryBuilder":
+ self._sample = sample
+ self._sample_offset = offset
+
  @staticmethod
  def _delete_sql(**kwargs: Any) -> str:
  return 'ALTER TABLE'
@@ -792,7 +802,12 @@ def _from_sql(self, with_namespace: bool = False, **kwargs: Any) -> str:
  selectable = ",".join(clause.get_sql(subquery=True, with_alias=True, **kwargs) for clause in self._from)
  if self._delete_from:
  return " {selectable} DELETE".format(selectable=selectable)
- return " FROM {selectable}".format(selectable=selectable)
+ clauses = [selectable]
+ if self._sample is not None:
+ clauses.append(f"SAMPLE {self._sample}")
+ if self._sample_offset is not None:
+ clauses.append(f"OFFSET {self._sample_offset}")
+ return " FROM {clauses}".format(clauses=" ".join(clauses))
 
  def _set_sql(self, **kwargs: Any) -> str:
  return " UPDATE {set}".format(

pypika/tests/dialects/test_clickhouse.py

@@ -13,6 +13,16 @@ def test_use_AS_keyword_for_alias(self):
  query = ClickHouseQuery.from_(t).select(t.foo.as_('f1'), t.bar.as_('f2'))
  self.assertEqual(str(query), 'SELECT "foo" AS "f1","bar" AS "f2" FROM "abc"')
 
+ def test_use_SAMPLE_keyword(self):
+ t = Table('abc')
+ query = ClickHouseQuery.from_(t).select(t.foo).sample(10)
+ self.assertEqual(str(query), 'SELECT "foo" FROM "abc" SAMPLE 10')
+
+ def test_use_SAMPLE_with_offset_keyword(self):
+ t = Table('abc')
+ query = ClickHouseQuery.from_(t).select(t.foo).sample(10, 5)
+ self.assertEqual(str(query), 'SELECT "foo" FROM "abc" SAMPLE 10 OFFSET 5')
+
 
 class ClickHouseDeleteTests(TestCase):
  table_abc = Table("abc")