[HBASE-23678] Literate builder API for version management in schema

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-1, 2.3.0, 1.7.0

Release Note

ColumnFamilyDescriptor new builder API:

    /**
     * Retain all versions for a given TTL(retentionInterval), and then only a specific number
     * of versions(versionAfterInterval) after that interval elapses.
     *
     * @param retentionInterval Retain all versions for this interval
     * @param versionAfterInterval Retain no of versions to retain after retentionInterval
     */
    public ModifyableColumnFamilyDescriptor setVersionsWithTimeToLive(
        final int retentionInterval, final int versionAfterInterval)

• Assignee: Viraj Jasani
• Reporter: Andrew Kyle Purtell
• Created: 10/Jan/20 19:21
• Updated: 14/Jul/20 18:36
• Resolved: 01/Apr/20 12:07

Description

Lars designed the combination of VERSIONS, TTL, MIN_VERSIONS, and KEEP_DELETED_CELLS with a maximum of flexibility. There is a lot of nuance regarding their usage. Almost all combinations of these four settings make sense for some use cases (exceptions are MIN_VERSIONS > 0 without TTL, and KEEP_DELETED_CELLS=TTL without TTL). There should be a way to make the behavior with TTL easier to conceive when creating the schema. This could take the form of a literate builder API for ColumnDescriptor or an extension to an existing one.

Let me give you a motivating example: We may want to retain all versions for a given TTL, and then only a specific number of versions after that interval elapses. This can be achieved with VERSIONS=INT_MAX, TTL=retention_interval, KEEP_DELETED_CELLS=TTL, MIN_VERSIONS=num_versions . This is not intuitive though because VERSIONS has been used to specify the number of versions to retain (num_versions in this example) since HBase version 0.1, so this is going to be a source of confusion - I've seen it in practice.

A literate builder API, by way of the way we design its method names, could let a user describe more or less in speaking language how they want version retention to work, and internally the builder API could set the low level schema attributes.

Issue Links

• links to: GitHub Pull Request #1381