fix: allow dispatching items to nested tables when specified parent_table_name equals resource.table_name

[joscha]

Description

I am trying to dispatch items from one resource to different tables, but connect them via a _dlt_parent_id reference.

Expected

Two tables.

my_table:

_dlt_id	id
xxx	1

other_table:

_dlt_id	_dlt_parent_id	id
yyy	xxx	10

however instead the test case in this PR yields an exception:

E           dlt.pipeline.exceptions.PipelineStepFailed: Pipeline execution failed at stage extract when processing package 1732801491.314115 with exception:
E
E           <class 'dlt.common.schema.exceptions.TablePropertiesConflictException'>
E           In schema: pipe_90aea10afd1f0c9f22f9154408b787ba: Cannot merge partial tables into table `my_other_table` due to property `resource` with different values: "my_table" != "my_table"

Where the error gets thrown, there is a comment:

dlt/dlt/common/schema/utils.py

Line 513 in eefe77b

# this should not really happen

:-D

And as you can see from the error message, the assertion is not quite right:

with different values: "my_table" != "my_table"

A few ideas:

1. Am I holding it wrong? If yes, how can we prevent other people from doing the same?
2. Should the error only be raised if the specified parent_table_name is ACTUALLY different from the table_name of the enclosing resource?

My feeling is 2., but I am not 100% sure. The test passes with my proposed change.

You can run the test via:

poetry run pytest -s tests/pipeline/test_pipeline.py -k test_mark_parent_table

There is a commented out chunk of code that does something similar actually and raises the same exception:

dlt/dlt/common/schema/utils.py

Lines 522 to 531 in eefe77b

	# def compare_tables(tab_a: TTableSchema, tab_b: TTableSchema) -> bool:
	# try:
	# table_name = tab_a["name"]
	# if table_name != tab_b["name"]:
	# raise TablePropertiesConflictException(table_name, "name", table_name, tab_b["name"])
	# diff_table = diff_tables(tab_a, tab_b, ignore_table_name=False)
	# # columns cannot differ
	# return len(diff_table["columns"]) == 0
	# except SchemaException:
	# return False

---

On a side note, I did just notice that there is no _dlt_parent_id in my_other_table with this test case, it looks like this:

 {'my_other_table': [{'id': 10, '_dlt_load_id': '1732802504.14759', '_dlt_id': 'IUDf2Ch1OievNg'}]}

unsure where to pass the hint to create the parent child relationship.

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[joscha]

@sh-rp or @burnash can I get your 👀 on this, please? I think it might potentially be a simple fix to accept. Tests are green, no changes to current behavior.