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Insert Metadata

Metadata is data about your data. In some use cases, you may need to insert data about your data into your dataset for downstream consumption.

For example, you might decide that one or more of the following types of information about your dataset should be tracked:

  • Source system(s)

  • Source filepath and filename (for non-uploaded files)

  • Source creation date

  • Date of import

  • Date of wrangling

  • Name of person who performed the wrangling

This section provides some methods for how to insert metadata into your dataset.

Insert filepath

For file-based data sources that were loaded from a dedicated storage layer, you can insert the path to the source file in your dataset using the $filepath reference.

提示

Filepath information can be lost when multi-dataset operations, such as unions and joins, are performed on your dataset. These steps should be added very early in your recipe.

In your recipe, insert the following transformation:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

$filepath

Parameter: New column name

sourceDatasetPath

Insert source row number

You can insert the row number in the source file from which rows in your dataset are sourced, using the $sourcerownumber reference.

提示

Source row number information can be lost when multi-dataset operations, such as unions and joins, are performed on your dataset. These steps should be added very early in your recipe.

In your recipe, insert the following transformation:

Transformation Name

New formula

Parameter: Formula type

Single row formula

Parameter: Formula

$sourcerownumber

Parameter: New column name

sourceRowNumber

提示

Tip: Use the ROWNUMBER function to derive the current row number in your dataset.

Insert a single metadata column

The following example describes how to insert a single column of metadata. In this case, the full path to the source is inserted as a new column in the dataset.

Steps:

  1. In the Dataset page, locate the imported dataset that is the source for your recipe. Click the Imported filter to show only the imported datasets.

  2. For the imported dataset, click Details.

  3. In the Dataset Details page, select the entire value for the Location, which is the storage location of the source.

    提示

    If the full path of the dataset is too long for screen display, be sure to include the ellipsis (...) at the end of the Location value.

  4. Copy the value. Paste the value into a text editor. You should see the full path, like the following:

    <root_dir>/uploads/1/2580298d-3477-4907-bfa7-f71978eace04/SF Restaurants - businesses.csv

  5. Load the dataset in the Transformer page.

  6. Specify the following transformation:

    Transformation Name

    New formula

    Parameter: Formula type

    Single row formula

    Parameter: Formula

    '<root_dir>\/uploads\/1\/2580298d-3477-4907-bfa7-f71978eace04\/SF Restaurants - businesses.csv'

    Parameter: New column name

    datasetPath

Insert multiple columns of metadata

You might need to track more fields of dataset information. While you might be able to perform these kinds of individual inserts, it might be easier to build this information from a separate file.

注意

This method uses the FILL function, which should be limited to smaller datasets when applied with a single key. Otherwise, there might be performance impacts when running the job against the full dataset.

提示

You can perform a similar merging of datasets using the Join datasets transformation. See Join Data.

For example, you want to track the following fields as metadata:

  • source_system

  • source_author

  • source_date_create

You could create a CSV file that looks like the following:

source_system,source_author,source_date_create
Excel,Joe Guy,12/9/15

In this case, the column headers are in the first line, and the values for each column are in the second line.

Steps:

  1. Use your CSV file as the source for a new dataset within the flow containing the associated dataset.

  2. In the data grid, make sure that the first line of data is treated as the header. If not, add a header transform to your recipe.

  3. Open the other (source) dataset in the Transformer page.

  4. In the recipe panel of the Transformer page, add a new step. In the Transformation textbox, enter union.

  5. Create a union using the Union transformation:

    1. Include all columns from both datasets.

    2. Configure the step to perform the union by name, instead of by position.

  6. Add this step to your recipe.

  7. You should see one row in the union recipe that contains the new data.

  8. Sort your data by a key value (e.g. business_id).

  9. Determine an appropriate grouping parameter. This step is necessary to simplify the filling process when the job runs at scale. Ideally, you should choose a grouping column that contains a relative few number of values in it (e.g. region).

  10. Fill values in the data rows with metadata column values. For each metadata column, add the following transformation, done here for the source_system column of metadata.

    Transformation Name

    Window

    Parameter: Formula

    FILL(source_system)

    Parameter: Group by

    region

    Parameter: Order by

    business_id

  11. Repeat the above step for each metadata column you want to insert.

  12. Delete the source metadata columns.

  13. Rename the window columns to use a more appropriate name.

  14. Delete the row containing the original metadata values.

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