Escaping the user's SQL in the explore view (#3186)

* Escaping the user's SQL in the explore view

When executing SQL from SQL Lab, we use a lower level API to the
database which doesn't require escaping the SQL. When going through
the explore view, the stack chain leading to the same method may need
escaping depending on how the DBAPI driver is written, and that is the
case for Presto (and perhaps other drivers).

* Using regex to avoid doubling doubles

superset/connectors/sqla/models.py

@@ -285,10 +285,12 @@ class SqlaTable(Model, BaseDatasource):
         """
         cols = {col.column_name: col for col in self.columns}
         target_col = cols[column_name]
+        tp = self.get_template_processor()
+        db_engine_spec = self.database.db_engine_spec
 
         qry = (
             select([target_col.sqla_col])
-            .select_from(self.get_from_clause())
+            .select_from(self.get_from_clause(tp, db_engine_spec))
             .distinct(column_name)
         )
         if limit:
@@ -322,7 +324,6 @@ class SqlaTable(Model, BaseDatasource):
         )
         logging.info(sql)
         sql = sqlparse.format(sql, reindent=True)
-        sql = self.database.db_engine_spec.sql_preprocessor(sql)
         return sql
 
     def get_sqla_table(self):
@@ -331,12 +332,14 @@ class SqlaTable(Model, BaseDatasource):
             tbl.schema = self.schema
         return tbl
 
-    def get_from_clause(self, template_processor=None):
+    def get_from_clause(self, template_processor=None, db_engine_spec=None):
         # Supporting arbitrary SQL statements in place of tables
         if self.sql:
             from_sql = self.sql
             if template_processor:
                 from_sql = template_processor.process_template(from_sql)
+            if db_engine_spec:
+                from_sql = db_engine_spec.escape_sql(from_sql)
             return TextAsFrom(sa.text(from_sql), []).alias('expr_qry')
         return self.get_sqla_table()
 
@@ -367,13 +370,14 @@ class SqlaTable(Model, BaseDatasource):
             'form_data': form_data,
         }
         template_processor = self.get_template_processor(**template_kwargs)
+        db_engine_spec = self.database.db_engine_spec
 
         # For backward compatibility
         if granularity not in self.dttm_cols:
             granularity = self.main_dttm_col
 
         # Database spec supports join-free timeslot grouping
-        time_groupby_inline = self.database.db_engine_spec.time_groupby_inline
+        time_groupby_inline = db_engine_spec.time_groupby_inline
 
         cols = {col.column_name: col for col in self.columns}
         metrics_dict = {m.metric_name: m for m in self.metrics}
@@ -428,7 +432,7 @@ class SqlaTable(Model, BaseDatasource):
                 groupby_exprs += [timestamp]
 
             # Use main dttm column to support index with secondary dttm columns
-            if self.database.db_engine_spec.time_secondary_columns and \
+            if db_engine_spec.time_secondary_columns and \
                     self.main_dttm_col in self.dttm_cols and \
                     self.main_dttm_col != dttm_col.column_name:
                 time_filters.append(cols[self.main_dttm_col].
@@ -438,7 +442,7 @@ class SqlaTable(Model, BaseDatasource):
         select_exprs += metrics_exprs
         qry = sa.select(select_exprs)
 
-        tbl = self.get_from_clause(template_processor)
+        tbl = self.get_from_clause(template_processor, db_engine_spec)
 
         if not columns:
             qry = qry.group_by(*groupby_exprs)

superset/db_engine_specs.py

@@ -73,6 +73,11 @@ class BaseEngineSpec(object):
         """Returns engine-specific table metadata"""
         return {}
 
+    @classmethod
+    def escape_sql(cls, sql):
+        """Escapes the raw SQL"""
+        return sql
+
     @classmethod
     def convert_dttm(cls, target_type, dttm):
         return "'{}'".format(dttm.strftime('%Y-%m-%d %H:%M:%S'))
@@ -139,14 +144,6 @@ class BaseEngineSpec(object):
         """
         return uri
 
-    @classmethod
-    def sql_preprocessor(cls, sql):
-        """If the SQL needs to be altered prior to running it
-
-        For example Presto needs to double `%` characters
-        """
-        return sql
-
     @classmethod
     def patch(cls):
         pass
@@ -399,6 +396,10 @@ class PrestoEngineSpec(BaseEngineSpec):
             uri.database = database
         return uri
 
+    @classmethod
+    def escape_sql(cls, sql):
+        return re.sub(r'%%|%', "%%", sql)
+
     @classmethod
     def convert_dttm(cls, target_type, dttm):
         tt = target_type.upper()

superset/sql_lab.py

@@ -154,7 +154,6 @@ def execute_sql(ctask, query_id, return_results=True, store_results=False):
         template_processor = get_template_processor(
             database=database, query=query)
         executed_sql = template_processor.process_template(executed_sql)
-        executed_sql = db_engine_spec.sql_preprocessor(executed_sql)
     except Exception as e:
         logging.exception(e)
         msg = "Template rendering failed: " + utils.error_msg_from_exception(e)