Behavior: Get column info from information_schema Part I

CHANGELOG.md

@@ -11,6 +11,7 @@
   - custom aliases for source and target tables can be specified and used in condition clauses;
   - `matched` and `not matched` steps can now be skipped;
 - Allow for the use of custom constraints, using the `custom` constraint type with an `expression` as the constraint (thanks @roydobbe). ([792](https://github.com/databricks/dbt-databricks/pull/792))
+- Add "use_info_schema_for_columns" behavior flag to turn on use of information_schema to get column info where possible. This may have more latency but will not truncate complex data types the way that 'describe' can. ([808](https://github.com/databricks/dbt-databricks/pull/808))
 
 ### Under the Hood
 

dbt/adapters/databricks/behaviors/columns.py

@@ -0,0 +1,71 @@
+from abc import ABC, abstractmethod
+from typing import List
+from dbt.adapters.sql import SQLAdapter
+from dbt.adapters.databricks.column import DatabricksColumn
+from dbt.adapters.databricks.relation import DatabricksRelation
+from dbt.adapters.databricks.utils import handle_missing_objects
+from dbt_common.utils.dict import AttrDict
+
+GET_COLUMNS_COMMENTS_MACRO_NAME = "get_columns_comments"
+
+
+class GetColumnsBehavior(ABC):
+    @classmethod
+    @abstractmethod
+    def get_columns_in_relation(
+        cls, adapter: SQLAdapter, relation: DatabricksRelation
+    ) -> List[DatabricksColumn]:
+        pass
+
+    @staticmethod
+    def _get_columns_with_comments(
+        adapter: SQLAdapter, relation: DatabricksRelation, macro_name: str
+    ) -> List[AttrDict]:
+        return list(
+            handle_missing_objects(
+                lambda: adapter.execute_macro(macro_name, kwargs={"relation": relation}),
+                AttrDict(),
+            )
+        )
+
+
+class GetColumnsByDescribe(GetColumnsBehavior):
+    @classmethod
+    def get_columns_in_relation(
+        cls, adapter: SQLAdapter, relation: DatabricksRelation
+    ) -> List[DatabricksColumn]:
+        rows = cls._get_columns_with_comments(adapter, relation, "get_columns_comments")
+        return cls._parse_columns(rows)
+
+    @classmethod
+    def _parse_columns(cls, rows: List[AttrDict]) -> List[DatabricksColumn]:
+        columns = []
+
+        for row in rows:
+            if row["col_name"].startswith("#"):
+                break
+            columns.append(
+                DatabricksColumn(
+                    column=row["col_name"], dtype=row["data_type"], comment=row["comment"]
+                )
+            )
+
+        return columns
+
+
+class GetColumnsByInformationSchema(GetColumnsByDescribe):
+    @classmethod
+    def get_columns_in_relation(
+        cls, adapter: SQLAdapter, relation: DatabricksRelation
+    ) -> List[DatabricksColumn]:
+        if relation.is_hive_metastore() or relation.type == DatabricksRelation.View:
+            return super().get_columns_in_relation(adapter, relation)
+
+        rows = cls._get_columns_with_comments(
+            adapter, relation, "get_columns_comments_via_information_schema"
+        )
+        return cls._parse_columns(rows)
+
+    @classmethod
+    def _parse_columns(cls, rows: List[AttrDict]) -> List[DatabricksColumn]:
+        return [DatabricksColumn(column=row[0], dtype=row[1], comment=row[2]) for row in rows]

dbt/adapters/databricks/impl.py

@@ -1,3 +1,4 @@
+from multiprocessing.context import SpawnContext
 import os
 import re
 from abc import ABC
@@ -7,7 +8,6 @@
 from contextlib import contextmanager
 from dataclasses import dataclass
 from typing import Any
-from typing import Callable
 from typing import cast
 from typing import ClassVar
 from typing import Dict
@@ -21,7 +21,6 @@
 from typing import Tuple
 from typing import Type
 from typing import TYPE_CHECKING
-from typing import TypeVar
 from typing import Union
 
 from dbt.adapters.base import AdapterConfig
@@ -37,6 +36,11 @@
 from dbt.adapters.contracts.connection import Connection
 from dbt.adapters.contracts.relation import RelationConfig
 from dbt.adapters.contracts.relation import RelationType
+from dbt.adapters.databricks.behaviors.columns import (
+    GetColumnsBehavior,
+    GetColumnsByDescribe,
+    GetColumnsByInformationSchema,
+)
 from dbt.adapters.databricks.column import DatabricksColumn
 from dbt.adapters.databricks.connections import DatabricksConnectionManager
 from dbt.adapters.databricks.connections import DatabricksDBTConnection
@@ -63,7 +67,7 @@
     StreamingTableConfig,
 )
 from dbt.adapters.databricks.relation_configs.tblproperties import TblPropertiesConfig
-from dbt.adapters.databricks.utils import get_first_row
+from dbt.adapters.databricks.utils import get_first_row, handle_missing_objects
 from dbt.adapters.databricks.utils import redact_credentials
 from dbt.adapters.databricks.utils import undefined_proof
 from dbt.adapters.relation_configs import RelationResults
@@ -73,8 +77,7 @@
 from dbt.adapters.spark.impl import KEY_TABLE_STATISTICS
 from dbt.adapters.spark.impl import LIST_SCHEMAS_MACRO_NAME
 from dbt.adapters.spark.impl import SparkAdapter
-from dbt.adapters.spark.impl import TABLE_OR_VIEW_NOT_FOUND_MESSAGES
-from dbt_common.exceptions import DbtRuntimeError
+from dbt_common.behavior_flags import BehaviorFlag
 from dbt_common.utils import executor
 from dbt_common.utils.dict import AttrDict
 
@@ -90,6 +93,15 @@
 SHOW_VIEWS_MACRO_NAME = "show_views"
 GET_COLUMNS_COMMENTS_MACRO_NAME = "get_columns_comments"
 
+USE_INFO_SCHEMA_FOR_COLUMNS = BehaviorFlag(
+    name="use_info_schema_for_columns",
+    default=False,
+    description=(
+        "Use info schema to gather column information to ensure complex types are not truncated."
+        "  Incurs some overhead, so disabled by default."
+    ),
+)  # type: ignore[typeddict-item]
+
 
 @dataclass
 class DatabricksConfig(AdapterConfig):
@@ -116,26 +128,6 @@ class DatabricksConfig(AdapterConfig):
     merge_with_schema_evolution: Optional[bool] = None
 
 
-def check_not_found_error(errmsg: str) -> bool:
-    new_error = "[SCHEMA_NOT_FOUND]" in errmsg
-    old_error = re.match(r".*(Database).*(not found).*", errmsg, re.DOTALL)
-    found_msgs = (msg in errmsg for msg in TABLE_OR_VIEW_NOT_FOUND_MESSAGES)
-    return new_error or old_error is not None or any(found_msgs)
-
-
-T = TypeVar("T")
-
-
-def handle_missing_objects(exec: Callable[[], T], default: T) -> T:
-    try:
-        return exec()
-    except DbtRuntimeError as e:
-        errmsg = getattr(e, "msg", "")
-        if check_not_found_error(errmsg):
-            return default
-        raise e
-
-
 def get_identifier_list_string(table_names: Set[str]) -> str:
     """Returns `"|".join(table_names)` by default.
 
@@ -175,6 +167,19 @@ class DatabricksAdapter(SparkAdapter):
         }
     )
 
+    get_column_behavior: GetColumnsBehavior
+
+    def __init__(self, config: Any, mp_context: SpawnContext) -> None:
+        super().__init__(config, mp_context)
+        if self.behavior.use_info_schema_for_columns.no_warn:  # type: ignore[attr-defined]
+            self.get_column_behavior = GetColumnsByInformationSchema()
+        else:
+            self.get_column_behavior = GetColumnsByDescribe()
+
+    @property
+    def _behavior_flags(self) -> List[BehaviorFlag]:
+        return [USE_INFO_SCHEMA_FOR_COLUMNS]
+
     # override/overload
     def acquire_connection(
         self, name: Optional[str] = None, query_header_context: Any = None
@@ -388,26 +393,7 @@ def parse_describe_extended(  # type: ignore[override]
     def get_columns_in_relation(  # type: ignore[override]
         self, relation: DatabricksRelation
     ) -> List[DatabricksColumn]:
-        rows = list(
-            handle_missing_objects(
-                lambda: self.execute_macro(
-                    GET_COLUMNS_COMMENTS_MACRO_NAME, kwargs={"relation": relation}
-                ),
-                AttrDict(),
-            )
-        )
-
-        columns = []
-        for row in rows:
-            if row["col_name"].startswith("#"):
-                break
-            columns.append(
-                DatabricksColumn(
-                    column=row["col_name"], dtype=row["data_type"], comment=row["comment"]
-                )
-            )
-
-        return columns
+        return self.get_column_behavior.get_columns_in_relation(self, relation)
 
     def _get_updated_relation(
         self, relation: DatabricksRelation

dbt/adapters/databricks/utils.py

@@ -8,6 +8,8 @@
 from typing import TypeVar
 
 from dbt.adapters.base import BaseAdapter
+from dbt.adapters.spark.impl import TABLE_OR_VIEW_NOT_FOUND_MESSAGES
+from dbt_common.exceptions import DbtRuntimeError
 from jinja2 import Undefined
 
 if TYPE_CHECKING:
@@ -92,3 +94,23 @@ def get_first_row(results: "Table") -> "Row":
 
         return Row(values=set())
     return results.rows[0]
+
+
+def check_not_found_error(errmsg: str) -> bool:
+    new_error = "[SCHEMA_NOT_FOUND]" in errmsg
+    old_error = re.match(r".*(Database).*(not found).*", errmsg, re.DOTALL)
+    found_msgs = (msg in errmsg for msg in TABLE_OR_VIEW_NOT_FOUND_MESSAGES)
+    return new_error or old_error is not None or any(found_msgs)
+
+
+T = TypeVar("T")
+
+
+def handle_missing_objects(exec: Callable[[], T], default: T) -> T:
+    try:
+        return exec()
+    except DbtRuntimeError as e:
+        errmsg = getattr(e, "msg", "")
+        if check_not_found_error(errmsg):
+            return default
+        raise e

dbt/include/databricks/macros/adapters/persist_docs.sql

@@ -28,6 +28,25 @@
   {% do return(load_result('get_columns_comments').table) %}
 {% endmacro %}
 
+{% macro get_columns_comments_via_information_schema(relation) -%}
+  {% call statement('repair_table', fetch_result=False) -%}
+    REPAIR TABLE {{ relation|lower }} SYNC METADATA
+  {% endcall %}
+  {% call statement('get_columns_comments_via_information_schema', fetch_result=True) -%}
+    select
+      column_name,
+      full_data_type,
+      comment
+    from `system`.`information_schema`.`columns`
+    where
+      table_catalog = '{{ relation.database|lower }}' and
+      table_schema = '{{ relation.schema|lower }}' and 
+      table_name = '{{ relation.identifier|lower }}'
+  {% endcall %}
+
+  {% do return(load_result('get_columns_comments_via_information_schema').table) %}
+{% endmacro %}
+
 {% macro databricks__persist_docs(relation, model, for_relation, for_columns) -%}
   {%- if for_relation and config.persist_relation_docs() and model.description %}
     {% do alter_table_comment(relation, model) %}

dev-requirements.txt

@@ -15,4 +15,4 @@ types-requests
 types-mock
 pre-commit
 
-dbt-tests-adapter~=1.8.0
+dbt-tests-adapter>=1.8.0, <2.0

requirements.txt

@@ -1,7 +1,8 @@
 databricks-sql-connector>=3.4.0, <3.5.0
 dbt-spark~=1.8.0
-dbt-core>=1.8.0, <2.0
-dbt-adapters>=1.3.0, <2.0
+dbt-core>=1.8.7, <2.0
+dbt-common>=1.10.0, <2.0
+dbt-adapters>=1.7.0, <2.0
 databricks-sdk==0.17.0
 keyring>=23.13.0
 protobuf<5.0.0

setup.py

@@ -55,9 +55,10 @@ def _get_plugin_version() -> str:
     include_package_data=True,
     install_requires=[
         "dbt-spark>=1.8.0, <2.0",
-        "dbt-core>=1.8.0, <2.0",
-        "dbt-adapters>=1.3.0, <2.0",
-        "databricks-sql-connector>=3.2.0, <3.3.0",
+        "dbt-core>=1.8.7, <2.0",
+        "dbt-adapters>=1.7.0, <2.0",
+        "dbt-common>=1.10.0, <2.0",
+        "databricks-sql-connector>=3.4.0, <3.5.0",
         "databricks-sdk==0.17.0",
         "keyring>=23.13.0",
         "pandas<2.2.0",

tests/conftest.py

@@ -7,7 +7,7 @@
 
 
 def pytest_addoption(parser):
-    parser.addoption("--profile", action="store", default="databricks_uc_sql_endpoint", type=str)
+    parser.addoption("--profile", action="store", default="databricks_uc_cluster", type=str)
 
 
 # Using @pytest.mark.skip_profile('databricks_cluster') uses the 'skip_by_adapter_type'

tests/functional/adapter/columns/fixtures.py

@@ -0,0 +1,25 @@
+base_model = """
+select struct('a', 1, 'b', 'b', 'c', ARRAY(1,2,3)) as struct_col, 'hello' as str_col
+"""
+
+schema = """
+version: 2
+models:
+  - name: base_model
+    config:
+        materialized: table
+    columns:
+      - name: struct_col
+      - name: str_col
+"""
+
+view_schema = """
+version: 2
+models:
+  - name: base_model
+    config:
+        materialized: view
+    columns:
+      - name: struct_col
+      - name: str_col
+"""