Errors¶

Engine errors¶

The engine raises one of three exception types. They are ordinary exceptions, so except Exception catches them.

Type	Raised when
`ur.UrsaError`	The base class. Catch it to catch every engine error.
`ur.ColumnNotFoundError`	A query names a column that the frame does not have. A subclass of `UrsaError`.
`ur.ComputeError`	A computation fails: an invalid parameter, an unsupported operation, or a kernel error. A subclass of `UrsaError`.

try:
    result = nodes.with_columns(pr=ur.pagerank(edges)).collect()
except ur.ColumnNotFoundError as exc:
    print(exc)

The message names the column or the parameter, and says what is valid.

Type	Raised when
`NotImplementedError`	The plan has a step, or a combination of steps, that does not run yet. See Limits.
`ValueError`	An argument is invalid before the plan runs: an unknown `on_null` value, an edge tuple of the wrong length, a filter on a column the frame does not have, or two aggregations with one name.
`ModuleNotFoundError`	`to_polars()` is called without `polars` installed. The message names the `ursa-graph[polars]` extra.
`RuntimeError`	A dataset download fails. See Datasets.

on_null="drop" emits a UserWarning with the number of rows it removed. Use the warnings module to silence it or to turn it into an error.