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I have a stream with incremental sync configured p...
# replication-ask-ai
l
I have a stream with incremental sync configured pagination is also configured however, when the page comes "empty", airbyte errors because I'm trying to add a field but it seems to fail if there are no records in the stream_slice airbyte_cdk.sources.concurrent_source.stream_thread_exception.StreamThreadException: Exception while syncing stream posicao_carteira: 'NoneType' object does not support item assignment
k
The knowledge sources don’t describe this exact 
StreamThreadException
pattern, so I can’t give a connector‑specific fix, but they do show similar 
NoneType
issues and how they arise. From the error: > 
'NoneType' object does not support item assignment
this usually means your code is doing something like:
Copy code
python stream_slice["some_field"] = value
at a point where 
stream_slice
is 
None
(for example, when a slice produced no records or when the CDK passes 
stream_slice=None
). Similar issues appear when code assumes state/slice is always present and tries to use it without checking for 
None
. [[Passing stream results](https://discuss.airbyte.io/t/2701); [Outreach issue](https://github.com/airbytehq/airbyte/issues/55253)] Given the constraints of the docs, here’s what you can safely do: 1. Guard against 
None
stream_slice
 Wherever you mutate or read 
stream_slice
, first check it:
Copy code
python    def path(self, stream_state=None, stream_slice=None, next_page_token=None, **kwargs):        if not stream_slice:            # fall back to a default path that does not depend on slice            return "your/base/path"         # safe to use stream_slice now        stream_slice["some_field"] = "value"        ...
Or, if you only need to read from it:
Copy code
python    if stream_slice:        account_id = stream_slice.get("account_id")
This is the same pattern used to fix a 
NoneType
slice in a custom connector where 
path()
assumed 
stream_slice
was always a dict. [[Passing stream results](https://discuss.airbyte.io/t/2701)] 2. Avoid mutating 
None
when a page is empty If your pagination or incremental logic updates state/slice when a page is empty, ensure you handle the “no records” case without writing into `stream_slice`:
Copy code
python    if not records:  # empty page        # update internal state or next_page_token, but don't touch stream_slice        return
3. Check any custom state logic Similar 
NoneType
errors also occur when code assumes 
stream_state
is always a dict and does 
if self.cursor_field in stream_state:
while 
stream_state
is 
None
. [[Outreach issue](https://github.com/airbytehq/airbyte/issues/55253)] If you have custom request options or pagination that read from 
stream_state
, guard it:
Copy code
python    if stream_state and self.cursor_field in stream_state:        ...
Because the knowledge sources don’t include your connector’s code, I can’t point to the exact line, but the fix will be to: - Find where you assign into 
stream_slice[...]
(or any dict you expect from the CDK), and - Add a 
None
check so that when a slice/page is empty, you don’t try to mutate 
None
. If you can share the specific method (e.g., 
path
, 
request_params
, or 
stream_slices
) where you add that field, I can help you adapt this pattern more concretely within those constraints.
l
@kapa.ai its on airbyte's python cdk (i'm using the builder interface), so I have no option maybe the CDK should check for empty slices before trying to add the field
k
A message from kapa.ai
You’re right that in the Builder you don’t have direct control over the Python CDK code, so you can’t just add 
if stream_slice is None
guards yourself. From the available knowledge sources, there isn’t an explicit mention of this exact 
StreamThreadException
/ “empty page + incremental + pagination” bug in the declarative/Builder stack, but there is a very similar class of issue where the CDK assumes a non‑`None` state/slice and then crashes with a 
NoneType
error. [[Outreach issue](https://github.com/airbytehq/airbyte/issues/55253)] In that case, the fix was in the CDK/connector implementation, not something the user could change from the UI. Given that: - You’re using Builder (declarative connector, no Python edits). - The error is coming from CDK internals (
concurrent_source.stream_thread_exception
and a 
NoneType
item assignment). - Similar 
NoneType
issues have required CDK/connector fixes upstream. [[Outreach issue](https://github.com/airbytehq/airbyte/issues/55253)] the most realistic path is: 1. Treat this as a bug in the CDK / Builder runtime Your suggestion (“CDK should check for empty slices before trying to add the field”) is aligned with how a previous 
NoneType
bug was handled: the fix was made in the CDK’s request/state handling code. [[Outreach issue](https://github.com/airbytehq/airbyte/issues/55253)] 2. Open an issue with Airbyte Since you can’t patch the generated Python, you’ll need the Airbyte team to adjust the CDK/Builder behavior. When you open the issue, include: - That this is a Builder‑created source. - The full stack trace including the line in 
concurrent_source
where the error occurs. - A description of the setup: incremental sync + pagination, and that the failure happens when a page/slice has no records. - Your connector definition (export the Builder YAML) if possible. Similar issues have been tracked and fixed via GitHub before. [[Outreach issue](https://github.com/airbytehq/airbyte/issues/55253)] 3. Interim workaround ideas (within Builder) The docs and forum posts don’t show a guaranteed workaround for this specific pattern in Builder, so I can’t recommend a precise configuration change with confidence. There is general guidance about nested streams and caching, but nothing that clearly addresses “empty page + incremental + pagination” in Builder. [[Passing stream results](https://discuss.airbyte.io/t/2701)] Because of that, I can’t honestly say “set option X in Builder and it will fix it” based on the current knowledge sources. So in short: this does look like something the CDK/Builder should handle more defensively, and the right next step is to file it as a bug with logs and your Builder config so the team can add the kind of 
None
checks you’re describing inside the CDK.
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