MongoDB: Apply special treatment to certain items

Some should be stored as lists, some need to be ignored for now.

CHANGES.md

@@ -12,6 +12,7 @@
   This means relevant column definitions will not be included into the SQL DDL.
 - MongoDB: Make `ctk load table` use the `data OBJECT(DYNAMIC)` mapping strategy.
 - MongoDB: Sanitize lists of varying objects
+- MongoDB: Apply special treatment to items that should be stored as lists
 
 ## 2024/09/02 v0.0.21
 - DynamoDB: Add special decoding for varied lists.

cratedb_toolkit/io/mongodb/copy.py

@@ -99,20 +99,23 @@ def start(self):
             progress_bar = tqdm(total=records_in)
             records_out = 0
 
-            for document in self.mongodb_collection.find().limit(self.mongodb_limit):
+            for document in self.mongodb_collection.find().skip(0).limit(self.mongodb_limit):
                 try:
                     operation = self.translator.to_sql(document)
                     logger.debug("SQL operation: %s", operation)
                 except Exception as ex:
                     logger_on_error(f"Transforming query failed: {ex}")
-                    continue
+                    # TODO: Make configurable.
+                    # raise
                 try:
                     result = connection.execute(sa.text(operation.statement), operation.parameters)
                     result_size = result.rowcount
                     records_out += result_size
                     progress_bar.update(n=result_size)
                 except Exception as ex:
-                    logger_on_error(f"Executing query failed: {ex}")
+                    logger_on_error(f"Executing query failed: {ex}\nOperation:\n{operation}")
+                    # TODO: Make configurable.
+                    # raise
 
             progress_bar.close()
             connection.commit()

cratedb_toolkit/io/mongodb/export.py

@@ -59,6 +59,40 @@ def timestamp_converter(value):
     "undefined": lambda x: None,
 }
 
+# TODO: Make configurable, for example by using a Zyp transformation definition.
+# Ignored items include anomalies not resolved yet.
+special_treatment_ignore_items = [
+    # Lists
+    "carrier_orders",
+    "contacts",
+    "equipment",
+    "flex_attributes",
+    # Maps
+    "status",
+    "customer",
+    "customers",
+    "customer_orders",
+    "customer_orders[]",
+    "sharing_meta_data",
+    "ship_locations",
+    "sort_attributes",
+    "start_date",
+    "end_date",
+]
+# New
+
+# Those items are fine after applying `to_list()`.
+special_treatment_to_list = [
+    "external_ids",
+    "flags",
+    "groupName",
+    "lane",
+    "po_number",
+]
+special_treatment_to_string = [
+    "custom_id",
+]
+
 
 def extract_value(value, parent_type=None):
     """
@@ -68,6 +102,8 @@ def extract_value(value, parent_type=None):
     - https://www.mongodb.com/docs/manual/reference/mongodb-extended-json/
     """
     if isinstance(value, dict):
+        # Custom adjustments to compensate shape errors in source data.
+        apply_special_treatments(value)
         if len(value) == 1:
             if "$binary" in value and value["$binary"]["subType"] in ["03", "04"]:
                 decoded = str(UUID(bytes=base64.b64decode(value["$binary"]["base64"])))
@@ -89,6 +125,39 @@ def extract_value(value, parent_type=None):
     return value
 
 
+def apply_special_treatments(value):
+    """
+    Apply special treatments to value that can't be described otherwise up until now.
+
+    TODO: Needs an integration test feeding two records instead of just one.
+    """
+
+    # Ignore certain items including anomalies that are not resolved, yet.
+    for ignore_name in special_treatment_ignore_items:
+        if ignore_name in value:
+            del value[ignore_name]
+
+    # Converge certain items to `list` even when defined differently.
+    for to_list_name in special_treatment_to_list:
+        if to_list_name in value and not isinstance(value[to_list_name], list):
+            value[to_list_name] = [value[to_list_name]]
+
+    # Converge certain items to `str` even when defined differently.
+    for name in special_treatment_to_string:
+        if name in value and not isinstance(value[name], str):
+            value[name] = str(value[name])
+
+    # Manual treatment.
+    # Some nested objects have been defined as strings, probably in previous schema versions.
+    if "users" in value:
+        for user_item in value["users"]:
+            if "user" in user_item and not isinstance(user_item["user"], dict):
+                user_item["user"] = {"id": user_item["user"]}
+
+    if "createdBy" in value and not isinstance(value["createdBy"], dict):
+        value["createdBy"] = {"id": value["createdBy"]}
+
+
 @define
 class ListOfVaryingObjectsSanitizer:
     """