[dagster-fivetran] Support fetch_column_metadata in FivetranWorkspace…

….sync_and_poll

python_modules/libraries/dagster-fivetran/dagster_fivetran/resources.py

@@ -2,6 +2,7 @@
 import logging
 import os
 import time
+from concurrent.futures import ThreadPoolExecutor
 from datetime import datetime, timedelta
 from functools import partial
 from typing import Any, Callable, Iterator, Mapping, Optional, Sequence, Tuple, Union
@@ -26,7 +27,10 @@
 from dagster._config.pythonic_config import ConfigurableResource
 from dagster._core.definitions.asset_spec import AssetSpec
 from dagster._core.definitions.definitions_load_context import StateBackedDefinitionsLoader
+from dagster._core.definitions.metadata.metadata_set import TableMetadataSet
+from dagster._core.definitions.metadata.table import TableColumn, TableSchema
 from dagster._core.definitions.resource_definition import dagster_maintained_resource
+from dagster._core.utils import imap
 from dagster._record import as_dict, record
 from dagster._utils.cached_method import cached_method
 from dagster._vendored.dateutil import parser
@@ -59,6 +63,9 @@
 FIVETRAN_API_VERSION_PATH = f"{FIVETRAN_API_VERSION}/"
 FIVETRAN_CONNECTOR_PATH = f"{FIVETRAN_CONNECTOR_ENDPOINT}/"
 
+DAGSTER_FIVETRAN_FETCH_COLUMN_METADATA_KEY = "dagster-fivetran/fetch_column_metadata"
+DEFAULT_MAX_THREADPOOL_WORKERS = 10
+
 # default polling interval (in seconds)
 DEFAULT_POLL_INTERVAL = 10
 
@@ -1029,6 +1036,9 @@ def sync_and_poll(
         assets_def = context.assets_def
         dagster_fivetran_translator = get_translator_from_fivetran_assets(assets_def)
 
+        # TODO: Add op tags to fivetran_assets decorator and build_fivetran_assets_definitions factory
+        fetch_column_metadata = context.op.tags.get(DAGSTER_FIVETRAN_FETCH_COLUMN_METADATA_KEY)
+
         connector_id = next(
             check.not_none(FivetranMetadataSet.extract(spec.metadata).connector_id)
             for spec in assets_def.specs
@@ -1040,26 +1050,81 @@ def sync_and_poll(
         )
 
         materialized_asset_keys = set()
-        for materialization in self._generate_materialization(
-            fivetran_output=fivetran_output, dagster_fivetran_translator=dagster_fivetran_translator
-        ):
-            # Scan through all tables actually created, if it was expected then emit a MaterializeResult.
-            # Otherwise, emit a runtime AssetMaterialization.
-            if materialization.asset_key in context.selected_asset_keys:
-                yield MaterializeResult(
-                    asset_key=materialization.asset_key, metadata=materialization.metadata
-                )
-                materialized_asset_keys.add(materialization.asset_key)
-            else:
-                context.log.warning(
-                    f"An unexpected asset was materialized: {materialization.asset_key}. "
-                    f"Yielding a materialization event."
-                )
-                yield materialization
 
-        unmaterialized_asset_keys = context.selected_asset_keys - materialized_asset_keys
-        if unmaterialized_asset_keys:
-            context.log.warning(f"Assets were not materialized: {unmaterialized_asset_keys}")
+        _map_fn: Callable[[AssetMaterialization], AssetMaterialization] = (
+            lambda materialization: self._fetch_and_attach_col_metadata(
+                connector_id, materialization
+            )
+            if fetch_column_metadata
+            else materialization
+        )
+        with ThreadPoolExecutor(
+            max_workers=DEFAULT_MAX_THREADPOOL_WORKERS,
+            thread_name_prefix=f"fivetran_{connector_id}",
+        ) as executor:
+            for materialization in imap(
+                executor=executor,
+                iterable=self._generate_materialization(
+                    fivetran_output=fivetran_output, dagster_fivetran_translator=dagster_fivetran_translator
+                ),
+                func=_map_fn,
+            ):
+                # Scan through all tables actually created, if it was expected then emit a MaterializeResult.
+                # Otherwise, emit a runtime AssetMaterialization.
+                if materialization.asset_key in context.selected_asset_keys:
+                    yield MaterializeResult(
+                        asset_key=materialization.asset_key,
+                        metadata=materialization.metadata
+                    )
+                    materialized_asset_keys.add(materialization.asset_key)
+                else:
+                    context.log.warning(
+                        f"An unexpected asset was materialized: {materialization.asset_key}."
+                        f"Yielding a materialization event."
+                    )
+                    yield materialization
+
+            unmaterialized_asset_keys = context.selected_asset_keys - materialized_asset_keys
+            if unmaterialized_asset_keys:
+                context.log.warning(f"Assets were not materialized: {unmaterialized_asset_keys}")
+
+    def _fetch_and_attach_col_metadata(
+        self, connector_id: str, materialization: AssetMaterialization
+    ) -> AssetMaterialization:
+        """Subroutine to fetch column metadata for a given table from the Fivetran API and attach it to the
+        materialization.
+        """
+        try:
+            schema_source_name = materialization.metadata["schema_source_name"].value
+            table_source_name = materialization.metadata["table_source_name"].value
+
+            table_conn_data = self.get_client().get_columns_for_table(
+                connector_id=connector_id,
+                schema_name=schema_source_name,
+                table_name=table_source_name,
+            )
+            columns = check.dict_elem(table_conn_data, "columns")
+            table_columns = sorted(
+                [
+                    TableColumn(name=col["name_in_destination"], type="")
+                    for col in columns.values()
+                    if "name_in_destination" in col and col.get("enabled")
+                ],
+                key=lambda col: col.name,
+            )
+            return materialization.with_metadata(
+                {
+                    **materialization.metadata,
+                    **TableMetadataSet(column_schema=TableSchema(table_columns)),
+                }
+            )
+        except Exception as e:
+            self._log.warning(
+                "An error occurred while fetching column metadata for table %s",
+                f"Exception: {e}",
+                exc_info=True,
+            )
+            return materialization
 
 
 @experimental