MySQL Data Redistribution

Publication

Bohyun Lee, Mijin An, Sangwon Lee, "A Case for Space Compaction of B-Tree Nodes on Flash Storage", IEEE Access Vol. 10 2022, April 2023
Publication Link

Motivation

While B-Tree is a ubiquitous index structure used in managing data, it is well known for its low space utilization in nodes. Such space under-utilization is detrimental to flash storage in terms of cost and performance. In particular, the logical space waste in B-tree will amplify physical writes inside flash storage, worsening the transaction throughput.

Contribution

Our evaluation results from running OLTP benchmarks(TPC-C) using the data redistribution MySQL clearly show that those optimizations improve transaction throughput (i.e., more than 50%) with less space and cost (i.e., less than 40%) in flash storage. Also the overall index space utilization is improved.

Prerequisites & Installation Guide

Install prerequisites of mysql-5.6.26. Follow the instructions in the site.
Clone this repository.

$ git clone https://github.com/FlashSQL/MySQL-Data-Redistribution.git

Run mysqld server to run MySQL.
Compare with Vanilla MySQL and see how table size changes

Implementation Details about Data Redistritbution

reserved free space are applied according to the record sizes and update pattern
added a new function in btr0btr.cc: btr_page_redistribute_before_split()
returns the inserted record
btr_page_redistribute_before_split() is called during btr_page_split_and_insert()(btr0btr.cc) before split is performed
modifications in srv0srv and fil0fil are for adding table id and table name

Future Work

We are planning to create additonal branches (MySQL-5.7, MySQL-5.8) for porting.

References

https://dev.mysql.com/

License

LeeBohyun/MySQL-Data-Redistribution

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