feat: add connector for CrateDB

docs/src/pages/docs/Connecting to Databases/crate.mdx

@@ -0,0 +1,25 @@
+---
+name: CrateDB
+menu: Connecting to Databases
+route: /docs/databases/cratedb
+index: 30
+version: 1
+---
+
+## CrateDB
+
+The recommended connector library for CrateDB is
+[crate](https://pypi.org/project/crate/).
+You need to install the extras as well for this library.
+We recommend adding something like the following
+text to your requirements file:
+
+```
+crate[sqlalchemy]==0.26.0
+```
+
+The expected connection string is formatted as follows:
+
+```
+crate://crate@127.0.0.1:4200
+```

setup.py

@@ -121,6 +121,7 @@ def get_git_sha():
         "clickhouse": ["clickhouse-sqlalchemy>= 0.1.4, <0.2"],
         "cockroachdb": ["cockroachdb>=0.3.5, <0.4"],
         "cors": ["flask-cors>=2.0.0"],
+        "crate": ["crate[sqlalchemy]>=0.26.0, <0.27"],
         "db2": ["ibm-db-sa>=0.3.5, <0.4"],
         "dremio": ["sqlalchemy-dremio>=1.1.5, <1.2"],
         "drill": ["sqlalchemy-drill==0.1.dev"],

superset/db_engine_specs/crate.py

@@ -0,0 +1,62 @@
+# 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 Optional, TYPE_CHECKING
+
+from superset.db_engine_specs.base import BaseEngineSpec
+from superset.utils import core as utils
+
+if TYPE_CHECKING:
+    from superset.connectors.sqla.models import TableColumn
+
+
+class CrateEngineSpec(BaseEngineSpec):
+
+    engine = "crate"
+    engine_name = "CrateDB"
+
+    _time_grain_expressions = {
+        None: "{col}",
+        "PT1S": "DATE_TRUNC('second', {col})",
+        "PT1M": "DATE_TRUNC('minute', {col})",
+        "PT1H": "DATE_TRUNC('hour', {col})",
+        "P1D": "DATE_TRUNC('day', {col})",
+        "P1W": "DATE_TRUNC('week', {col})",
+        "P1M": "DATE_TRUNC('month', {col})",
+        "P0.25Y": "DATE_TRUNC('quarter', {col})",
+        "P1Y": "DATE_TRUNC('year', {col})",
+    }
+
+    @classmethod
+    def epoch_to_dttm(cls) -> str:
+        return "{col} * 1000"
+
+    @classmethod
+    def epoch_ms_to_dttm(cls) -> str:
+        return "{col}"
+
+    @classmethod
+    def convert_dttm(cls, target_type: str, dttm: datetime) -> Optional[str]:
+        tt = target_type.upper()
+        if tt == utils.TemporalType.TIMESTAMP:
+            return f"{dttm.timestamp() * 1000}"
+        return None
+
+    @classmethod
+    def alter_new_orm_column(cls, orm_col: "TableColumn") -> None:
+        if orm_col.type == "TIMESTAMP":
+            orm_col.python_date_format = "epoch_ms"

tests/db_engine_specs/crate_tests.py

@@ -0,0 +1,51 @@
+# 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 superset.connectors.sqla.models import SqlaTable, TableColumn
+from superset.db_engine_specs.crate import CrateEngineSpec
+from superset.models.core import Database
+from tests.db_engine_specs.base_tests import TestDbEngineSpec
+
+
+class TestCrateDbEngineSpec(TestDbEngineSpec):
+    def test_convert_dttm(self):
+        """
+        DB Eng Specs (crate): Test conversion to date time
+        """
+        dttm = self.get_dttm()
+        assert CrateEngineSpec.convert_dttm("TIMESTAMP", dttm) == "1546398245678.9"
+
+    def test_epoch_to_dttm(self):
+        """
+        DB Eng Specs (crate): Test epoch to dttm
+        """
+        assert CrateEngineSpec.epoch_to_dttm() == "{col} * 1000"
+
+    def test_epoch_ms_to_dttm(self):
+        """
+        DB Eng Specs (crate): Test epoch ms to dttm
+        """
+        assert CrateEngineSpec.epoch_ms_to_dttm() == "{col}"
+
+    def test_alter_new_orm_column(self):
+        """
+        DB Eng Specs (crate): Test alter orm column
+        """
+        database = Database(database_name="crate", sqlalchemy_uri="crate://db")
+        tbl = SqlaTable(table_name="druid_tbl", database=database)
+        col = TableColumn(column_name="ts", type="TIMESTAMP", table=tbl)
+        CrateEngineSpec.alter_new_orm_column(col)
+        assert col.python_date_format == "epoch_ms"