• 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

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.

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.

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

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

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

• 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

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

• https://dev.mysql.com/