Table Reader (Labs)

This node reads files that have been written using the Table Writer node (which uses an internal format). It retains all meta information such as domain, properties, colors, size.

Options

Source

Select a file location which stores the data you want to read. When clicking on the browse button, there are two default file system options to choose from:

• The current Hub space: Allows to select a file relative to the Hub space on which the workflow is run.
• URL: Allows to specify a URL (e.g. file://, http:// or knime:// protocol).

Skip first data rows

Use this option to skip the specified number of valid data rows. This has no effect on which row will be chosen as a column header. Skipping rows prevents parallel reading of individual files.

Limit number of rows

If enabled, only the specified number of data rows are read. The column header row (if selected) is not taken into account. Limiting rows prevents parallel reading of individual files.

Maximum number of rows

Defines the maximum number of rows that are read.

Use existing RowID

Check this box if the RowIDs from the input tables should be used for the output tables. If unchecked, a new RowID is generated. The generated RowID follows the schema "Row0", "Row1" and so on.

If schema changes

Specifies the node behavior if the content of the configured file/folder changes between executions, i.e., columns are added/removed to/from the file(s) or their types change. The following options are available:

• Fail: If set, the node fails if the column names in the file have changed. Changes in column types will not be detected.
• Use new schema: If set, the node will compute a new table specification for the current schema of the file at the time when the node is executed. Note that the node will not output a table specification before execution and that it will not apply transformations, therefore the transformation tab is disabled.
• Ignore (deprecated): If set, the node tries to ignore the changes and outputs a table with the old table specification. This option is deprecated and should never be selected for new workflows, as it may lead to invalid data in the resulting table. Use one of the other options instead.

How to combine columns

Specifies how to deal with reading multiple files in which not all column names are identical.

• Fail if different: The node will fail if multiple files are read and not all files have the same column names.
• Union: Any column that is part of any input file is considered. If a file is missing a column, it is filled up with missing values.
• Intersection: Only columns that appear in all files are considered for the output table.

Prepend table index to RowID

Only enabled if the existing RowIDs are used. If checked, a prefix is prepended to the RowIDs that indicates which table the row came from. The format of the prefix is “File_0_“, “File_1_” and so on.

Append file path column

Select this box if you want to add a column containing the path of the file from which the row is read. The node will fail if adding the column with the provided name causes a name collision with any of the columns in the read table.

File path column name

The name of the column containing the file path.

Enforce types

Controls how columns whose type changes are dealt with. If selected, the mapping to the KNIME type you configured is attempted. The node will fail if that is not possible. If unselected, the KNIME type corresponding to the new type is used.

Transformations

Use this option to modify the structure of the table. You can deselect each column to filter it out of the output table, use the arrows to reorder the columns, or change the column name or column type of each column. Note that the positions of columns are reset in the dialog if a new file or folder is selected. Whether and where to add unknown columns during execution is specified via the special row <any unknown new column>. It is also possible to select the type new columns should be converted to. Note that the node will fail if this conversion is not possible e.g. if the selected type is Integer but the new column is of type Double.

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