pathwaycom/pathway · error · ValueError

Failed to find the column '{column._name}' in table {column.

Error message

Failed to find the column '{column._name}' in table {column._table}

What it means

ValueError raised when a ColumnReference used in a synchronization group has a name that is not found among the schema column names of its table. The code scans column._table._schema.column_names(); if the referenced column's name is absent, the reference cannot be mapped to a connector field index.

Source

Thrown at python/pathway/io/_synchronization.py:274

        else:
            column = synchronized_column.column
            priority = synchronized_column.priority
            idle_duration = synchronized_column.idle_duration
            if idle_duration is not None:
                idle_duration = datetime.timedelta(
                    seconds=as_duration_seconds(idle_duration, "idle_duration")
                )

        column_types.add(column._column.dtype)
        _check_column_type(column, max_difference)

        column_idx = None
        for index, field in enumerate(column._table._schema.column_names()):
            if field == column._name:
                column_idx = index
                break
        if column_idx is None:
            raise ValueError(
                f"Failed to find the column '{column._name}' in table {column._table}"
            )

        is_table_found = False
        for node in G._current_scope.nodes:
            if (
                not isinstance(node, InputOperator)
                or not isinstance(node.datasource, GenericDataSource)
                or node.outputs[0].value != column._table
            ):
                continue
            is_table_found = True
            group = api.ConnectorGroupDescriptor(
                name, column_idx, max_difference, priority, idle_duration
            )
            if node.datasource.data_source_options.synchronization_group is not None:
                raise ValueError(
                    "Only one column from a table can be used in a synchronization group"

View on GitHub (pinned to fa2f74a464)

Solutions

1. Use a column reference from the final table: sync(t_renamed.ts, other.time, ...) where t_renamed = t.rename_columns(ts='time')
2. Rebuild references after schema-changing transformations instead of reusing stale ones
3. Print table.schema to confirm the column names available on the table you pass

Example fix

// before
t2 = t.rename_columns(ts='time')
pw.io.synchronize(t.time, other.time, max_difference=600)  # t.time stale

// after
t2 = t.rename_columns(ts='time')
pw.io.synchronize(t2.time, other.time, max_difference=600)

def column_in_table_schema(col_ref, table) -> bool:
    return col_ref._name in list(table._schema.column_names())

When it happens

Trigger: Passing a column reference whose name was renamed (t.rename_columns(ts='time') then using the old reference), a column from a table whose schema was redefined, or a reference created before with_columns replaced the table. The loop over schema column_names finds no field == column._name.

Common situations: Renaming columns before calling the sync API; using a reference captured from the original table after with_columns/rename created a new table; typos in column names passed as references from helper functions.

Related errors

• can't generate Schema based on an empty CSV file
• columns do not match in the argument of Table.concat(). Miss
• Columns of the argument in Table.update_cells() not present
• Columns do not match between argument of Table.update_rows()
• Column {old_name} does not exist in a given table.

AI-assisted analysis of pathwaycom/pathway@fa2f74a464 (2026-08-15). Data as JSON: /api/errors/a1fef42a4b6c656d. Report an issue: GitHub.