[GitHub] [superset] Ceridan commented on a change in pull request #17898: feat: Add support for Azure Data Explorer (Kusto) db engine spec

[GitBox <gi...@apache.org>]

Ceridan commented on a change in pull request #17898:
URL: https://github.com/apache/superset/pull/17898#discussion_r778010575



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File path: superset/db_engine_specs/kustokql.py
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@@ -0,0 +1,115 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+from datetime import datetime
+from typing import Any, Dict, List, Optional, Type
+
+from sqlalchemy.engine import Engine
+
+from superset.db_engine_specs.base import BaseEngineSpec, LimitMethod
+from superset.db_engine_specs.exceptions import (
+    SupersetDBAPIDatabaseError,
+    SupersetDBAPIOperationalError,
+    SupersetDBAPIProgrammingError,
+)
+from superset.models.core import Database
+from superset.sql_parse import ParsedQuery
+from superset.utils import core as utils
+
+
+class KustoKqlEngineSpec(BaseEngineSpec):  # pylint: disable=abstract-method
+    limit_method = LimitMethod.WRAP_SQL
+    engine = "kustokql"
+    engine_name = "KustoKQL"
+    time_groupby_inline = True
+    time_secondary_columns = True
+    allows_joins = True
+    allows_subqueries = True
+    allows_sql_comments = False
+    run_multiple_statements_as_one = True
+
+    _time_grain_expressions = {
+        None: "{col}",
+        "PT1S": "{col}/ time(1s)",
+        "PT1M": "{col}/ time(1min)",
+        "PT1H": "{col}/ time(1h)",
+        "P1D": "{col}/ time(1d)",
+        "P1M": "datetime_diff('month',CreateDate, datetime(0001-01-01 00:00:00))+1",
+        "P1Y": "datetime_diff('year',CreateDate, datetime(0001-01-01 00:00:00))+1",
+    }
+
+    type_code_map: Dict[int, str] = {}  # loaded from get_datatype only if needed
+
+    @classmethod
+    def get_dbapi_exception_mapping(cls) -> Dict[Type[Exception], Type[Exception]]:
+        # pylint: disable=import-outside-toplevel,import-error
+        import sqlalchemy_kusto.errors as kusto_exceptions
+
+        return {
+            kusto_exceptions.DatabaseError: SupersetDBAPIDatabaseError,
+            kusto_exceptions.OperationalError: SupersetDBAPIOperationalError,
+            kusto_exceptions.ProgrammingError: SupersetDBAPIProgrammingError,
+        }
+
+    @classmethod
+    def convert_dttm(
+        cls, target_type: str, dttm: datetime, db_extra: Optional[Dict[str, Any]] = None
+    ) -> Optional[str]:
+        if target_type.upper() == utils.TemporalType.DATETIME:
+            return f"""datetime({dttm.isoformat(timespec="seconds")})"""
+        return None
+
+    @classmethod
+    def is_readonly_query(cls, parsed_query: ParsedQuery) -> bool:
+        """Pessimistic readonly, 100% sure statement won't mutate anything"""
+        return not parsed_query.sql.startswith(".")
+
+    @classmethod
+    def select_star(  # pylint: disable=too-many-arguments
+        cls,
+        database: Database,
+        table_name: str,
+        engine: Engine,
+        schema: Optional[str] = None,
+        limit: int = 100,
+        show_cols: bool = False,
+        indent: bool = True,
+        latest_partition: bool = True,
+        cols: Optional[List[Dict[str, Any]]] = None,
+    ) -> str:
+        return super().select_star(
+            database,
+            table_name,
+            engine,
+            None,
+            limit,
+            show_cols,
+            indent,
+            latest_partition,
+            cols,
+        )
+
+    @classmethod
+    def is_select_query(cls, parsed_query: ParsedQuery) -> bool:
+        return not parsed_query.sql.startswith(".")

Review comment:
       You are right. Kusto differentiates control commands and queries (data ingestions are considered as control commands too). Here is a quote from the [docs](https://docs.microsoft.com/en-us/azure/data-explorer/kusto/management/), how to differentiate control commands from queries on the language level:
   
   > At the language level, the first character of the text of a request determines if the request is a control command or a query. Control commands must start with the dot (.) character, and no query may start by that character.
   
   We performed this simple check in the `is_select_query` method.




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