pathwaycom/pathway · error · ValueError

SchemaRegistrySettings requires at least one entry in 'urls'

Error message

SchemaRegistrySettings requires at least one entry in 'urls'; got an empty list.

What it means

The Delta table optimizer tracks compaction activity against a specific column (its engine rule), and Delta optimization can only act on partitioned data. Therefore the tracked column must appear in partition_columns, otherwise the optimizer would track nothing useful.

Source

Thrown at python/pathway/internals/_io_helpers.py:280

    """

    urls: list[str]
    token_authorization: str | None = None
    username: str | None = None
    password: str | None = None
    headers: list[SchemaRegistryHeader] | None = None
    proxy: str | None = None
    timeout: datetime.timedelta | None = None

    def __post_init__(self):
        if not isinstance(self.urls, (list, tuple)):
            raise TypeError(
                f"SchemaRegistrySettings.urls must be a list of strings, "
                f"got {type(self.urls).__name__}. Wrap a single URL in a "
                f"list: urls=['http://...']."
            )
        if not self.urls:
            raise ValueError(
                "SchemaRegistrySettings requires at least one entry in 'urls'; "
                "got an empty list."
            )
        for i, url in enumerate(self.urls):
            if not isinstance(url, str) or not url:
                raise ValueError(
                    f"SchemaRegistrySettings.urls[{i}] must be a non-empty "
                    f"string; got {url!r}."
                )
        for field_name in ("token_authorization", "username", "password", "proxy"):
            value = getattr(self, field_name)
            if value is not None and not isinstance(value, str):
                raise TypeError(
                    f"SchemaRegistrySettings.{field_name} must be a str, "
                    f"got {type(value).__name__}."
                )
        if self.password is not None and self.username is None:
            raise ValueError(

View on GitHub (pinned to fa2f74a464)

Solutions

1. Add the optimizer's tracked column to partition_columns, e.g. partition_columns=[t.event_time, ...].
2. If partitioning by that column is unacceptable (cardinality too high), configure the optimizer to track an existing partition column instead.
3. Drop table_optimizer if no partition-based optimization is intended.

Example fix

# before
pw.io.deltalake.write(t, uri, partition_columns=[t.tenant], table_optimizer=pw.io.deltalake.DeltalakeCompactionOptimizer(tracked_column=t.event_time))

# after
pw.io.deltalake.write(t, uri, partition_columns=[t.tenant, t.event_time], table_optimizer=pw.io.deltalake.DeltalakeCompactionOptimizer(tracked_column=t.event_time))

if table_optimizer is not None:
    tracked = table_optimizer.tracked_column.name
    names = [c._name for c in partition_columns or []]
    assert tracked in names, (
        f"optimizer tracks '{tracked}' but partition_columns={names}"
    )
pw.io.deltalake.write(t, uri, partition_columns=partition_columns,
                      table_optimizer=table_optimizer)

When it happens

Trigger: Calling pw.io.deltalake.write(table, uri, partition_columns=[t.a], table_optimizer=SomeOptimizer(tracked_column=t.b)) where the optimizer's tracked column is not among partition_columns (or partition_columns is None/empty).

Common situations: User enables an optimizer (e.g. one tracking a timestamp column) but partitions by a different business column, or forgets partitioning entirely while adding the optimizer to speed up reads.

Related errors

• SchemaRegistrySettings.urls must be a list of strings, got {
• Failed to install dependencies
• Column {pseudocolumn} has to contain integers only.
• Column {api.TIME_PSEUDOCOLUMN} cannot contain negative times
• parameters `schema` and `id_from` are mutually exclusive

AI-assisted analysis of pathwaycom/pathway@fa2f74a464 (2026-08-15). Data as JSON: /api/errors/d14058449325b2f5. Report an issue: GitHub.