Transcoder Interface

The Transcoder interface may be used to provide custom value and key formats. Among the uses of the transcoder class, one may:

  • Implement compatibility with other client libraries

    The format option in the operations correspond to a flag value which is stored in the server as meta data along with the key. These flags are utilized by client libraries to determine how to interpret the value on the server (which is just a set of bytes) into a more complex and user-friendly type in the native client language. Some clients may have different ideas about which flags mean which value format, and some clients may use formats which are specific to that platform (for example, FMT_PICKLE which is typically only native to Python objects). One may implement a custom transcoder class which understands a wider variety of types and flags

  • Implement Compression

    If storing large values, it may be handy to compress them before storing them on the server. This provides for lower network overhead and storage space on the server, at the expense of the computational overhead of compressing and decompressing objects. One may add extra flags to indicate a value has been compressed, and with which format.

  • Automatic conversion of different value types into custom classes

    The built-in transcoder only uses native Python types. One may wish to interpret values as belong to user-defined classes.

The Transcoder class is implemented in C for efficiency, but a pure-python implementation is available as the TranscoderPP class in couchbase/

Typically one would subclass the Transcoder class, and implement the needed methods, allowing for high efficient built-in methods to perform the un-needed operations.

Note that the Client does not use a Transcoder object by default (however it internally uses the same routines that the C-implemented Transcoder does). Thus, if no custom transcoding is needed, it is more efficient to set the transcoder to None, which is the default.

class couchbase_core.transcoder.Transcoder