AttributeCompressor

Compresses and (optionally) encrypts the values of the specified attributes. The compressed and encrypted attribute values can be decompressed and decrypted using the AttributeDecompressor.

This transformer is particularly useful for compressing large blocks of XML, or geometry-storing attributes.

Jump to Configuration

Typical Uses

• Password-encrypt a value for storage in a database, for decryption with the AttributeDecompressor
• Compress large blocks of XML to optimize storage
• Compress large geometry for storage as blob fields to optimize storage

How does it work?

The AttributeCompressor lets you pick one, some, or all attributes to be compressed, and select the level of compression to apply. You can choose to encrypt the compressed attributes with a user-provided password, or leave them unencrypted. Features passing through the transformer are output with their attribute names unchanged, but the selected values compressed. The AttributeDecompressor can be used to read them, either elsewhere within the workspace or in a different workspace.

Example: Loading geometry to a database table as attributes

In this portion of a workspace, an input dataset with complex boundary polygons is to be loaded to a non-spatial database.

The first step is to extract the geometry and convert it to an attribute with the GeometryExtractor. Having selected WKT as the encoding type, the geometry is stored in the new attribute _geometry.

The features are then passed to the AttributeCompressor to optimize them for storage prior to writing to the database.

The features are then sent to the database writer, where the compressed attributes will be written as blobs and stored.

Example: Encrypting a value

In this portion of a workspace, a table of owners is written to a database.

Using the AttributeCompressor, the names and email addresses are password-encrypted for an added layer of personal information protection in the database.

In this example, the password is being created by a published user parameter that the user can assign as the workspace is run.

Usage Notes

• The AttributeCompressor uses the zlib library to provide basic compression, and the OpenSSL library to provide encryption.
• Different datasets have varying degrees of compressibility, and so results will vary.

Configuration

Input Ports

Input

Features with attributes.

Output Ports

Output

All attributes, compressed and uncompressed.

Parameters

Compression Parameters

Attributes to Compress	After connecting the transformer, click the browse button to select the attributes to be compressed and/or encrypted.
Compression Level	The value of this parameter controls the compression level which will be applied to the attributes. A value of 0 indicates that no compression should be used, while a value of 9 indicates that maximum compression should be used. The default value is 6.

Encryption Parameters

Encryption Type	Use this parameter to select an encryption type. Currently, only the AES-256 encryption algorithm is supported.
Password	If encryption is being used, the value of this parameter will be used to generate an encryption key. The same value may then be used to decrypt the attribute values in the AttributeDecompressor transformer.

Editing Transformer Parameters

Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.

Defining Values

There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.

How to Set Parameter Values

Using the Text Editor

The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.

Text Editor

Using the Arithmetic Editor

The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.

Arithmetic Editor

Conditional Values

Set values depending on one or more test conditions that either pass or fail.

Parameter Condition Definition Dialog

Content

Expressions and strings can include a number of functions, characters, parameters, and more - whether entered directly in a parameter or constructed using one of the editors.

Content Types

String Functions	These functions manipulate and format strings.
Special Characters	A set of control characters is available in the Text Editor.
Math Functions	Math functions are available in both editors.
Math Operators	These operators are available in the Arithmetic Editor.
FME Feature Functions	These return primarily feature-specific values.
FME Parameters	FME and workspace-specific parameters may be used.
Working with User Parameters	Create your own editable parameters.

Reference

Related Transformers

AttributeDecompressor

FME Knowledge Center

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Examples may contain information licensed under the Open Government Licence – Vancouver