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Why not supported range scans?

See original GitHub issue

Range scans is not supported for HaloDB. If I want to support range scans function, what should I do?

Issue Analytics

State:
Created 5 years ago
Comments:5

Top GitHub Comments

1reaction

amannalycommented, Sep 27, 2018

@shuaijunlan range scans are currently not supported. The workload for which HaloDB was designed for only does point lookups.

I haven’t given this problem much thought yet, but a possible approach could be to use an ordered index in memory. We should ideally not order the data on disk as this would increase read and write amplification for HaloDB, or might force us to do random writes.

HaloDB currently has an in-memory index, which is an off-heap concurrent hash table. To support range scans we could use a ConcurrentSkipList as the index, but since HaloDB need to handle large data sets we need an implementation of the skip list which does memory allocation outside the heap. More research is needed to figure out how this will perform and the resources it will consume.

This is probably a big effort, and I don’t plan do this immediately.

0reactions

ShuaiJunlancommented, Sep 27, 2018

@amannaly Thank you for your guidance. Is there a more detailed document about HaloDB designing?

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