[db-engine-spec] Aligning Hive/Presto partition logic (apache#7007)

superset/db_engine_specs.py

@@ -986,16 +986,16 @@ def where_latest_partition(
  except Exception:
  # table is not partitioned
  return False
- for c in columns:
- if c.get('name') == col_name:
- return qry.where(Column(col_name) == value)
+ if value is not None:
+ for c in columns:
+ if c.get('name') == col_name:
+ return qry.where(Column(col_name) == value)
  return False
 
  @classmethod
  def _latest_partition_from_df(cls, df):
- recs = df.to_records(index=False)
- if recs:
- return recs[0][0]
+ if not df.empty:
+ return df.to_records(index=False)[0][0]
 
  @classmethod
  def latest_partition(cls, table_name, schema, database, show_first=False):
@@ -1012,7 +1012,7 @@ def latest_partition(cls, table_name, schema, database, show_first=False):
  :type show_first: bool
 
  >>> latest_partition('foo_table')
- '2018-01-01'
+ ('ds', '2018-01-01')
  """
  indexes = database.get_indexes(table_name, schema)
  if len(indexes[0]['column_names']) < 1:
@@ -1330,9 +1330,10 @@ def where_latest_partition(
  except Exception:
  # table is not partitioned
  return False
- for c in columns:
- if c.get('name') == col_name:
- return qry.where(Column(col_name) == value)
+ if value is not None:
+ for c in columns:
+ if c.get('name') == col_name:
+ return qry.where(Column(col_name) == value)
  return False
 
  @classmethod
@@ -1343,7 +1344,8 @@ def latest_sub_partition(cls, table_name, schema, database, **kwargs):
  @classmethod
  def _latest_partition_from_df(cls, df):
  """Hive partitions look like ds={partition name}"""
- return df.ix[:, 0].max().split('=')[1]
+ if not df.empty:
+ return df.ix[:, 0].max().split('=')[1]
 
  @classmethod
  def _partition_query(