[Java] Improving Arrow Vector Reading performance

[asfimport]

Currently the read interface of Java Arrow Vector is quite slow because the access operation has to go through validity bit check and boundary check before it can actually load the data. Such a safety check incurs unnecessary overhead in actually computation. 

The Arrow Vector and ArrowBuf should expose unsafe methods for advanced users to directly access underlying data without null check and boundary check.

Reporter: Yurui Zhou / @yuruiz

Subtasks:

• [Java] Add hasNull flag to Vectors
• [Java] Add unsafe access method to ArrowBuf

Related issues:

• [Java] Add accessor methods for data buffers that skip null checking (relates to)
• [Java] Provide light-weight arrow APIs (is related to)

PRs and other links:

• GitHub Pull Request apache/arrow#4199

_{Note: This issue was originally created as ARROW-5197. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
Possibly duplicate of ARROW-1833, I added a link to this JIRA

[asfimport]

Yurui Zhou / @yuruiz:
oh yeah, you are right. There may some overlap on the work. 

[asfimport]

Micah Kornfield / @emkornfield:
[~Yurui Zhou] I think all of these JIRAs can be resolved, since there is functionality in the code base to achieve them?

[asfimport]

Todd Farmer / @toddfarmer:
This issue was last updated over 90 days ago, which may be an indication it is no longer being actively worked. To better reflect the current state, the issue is being unassigned. Please feel free to re-take assignment of the issue if it is being actively worked, or if you plan to start that work soon.