[MAHOUT-162] Added support for mapping String to long IDs in CF code

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.2
• Fix Version/s: 0.2
• Assignee: Sean R. Owen
• Reporter: Sean R. Owen
• Due: 21/Aug/09
• Created: 11/Aug/09 12:58
• Updated: 31/Jan/24 22:11
• Resolved: 17/Aug/09 16:53

Description

Since the framework now only allows long (64-bit integer) IDs, and no longer Strings, we need to provide some support for translating between the two. The basic proposal is this:

• Define a one-way mapping from Strings to longs that is repeatable and easy to implement in many contexts. In particular I propose using the bottom 64 bits of the MD5 hash of a string.
• Define support for storing the reverse mapping (longs to Strings) in various ways, in an efficient way, that handles gracefully the very rare possibility of collision

Issue Links

• depends upon: MAHOUT-158 Replace all ID values with long