XiangpengHao opened a new issue, #6094: URL: https://github.com/apache/arrow-rs/issues/6094
**Is your feature request related to a problem or challenge? Please describe what you are trying to do.** <!-- A clear and concise description of what the problem is. Ex. I'm always frustrated when [...] (This section helps Arrow developers understand the context and *why* for this feature, in addition to the *what*) --> Related to https://github.com/apache/datafusion/issues/10918 and https://github.com/apache/arrow-rs/issues/5374 Current default block size (i.e., buffer capacity) is 8KB, it is a reasonable initial value -- we only waste up to 8KB of data. However, it is not great for large `StringViewArray`s. With default 8KB block size , 4GB of strings will require half a million buffers, causing a significant slowdown even for APIs like [`get_array_memory_size`](https://github.com/apache/arrow-rs/blob/master/arrow-array/src/array/byte_view_array.rs#L397) We want to have a small number of buffers for the following reasons: (1) faster buffer lookup due to better `Vec<Buffer>` locality, and (2) faster concatenation. Query engines (e.g., DataFusion) often need to concatenate multiple batches, which needs to concatenate two `Vec<Buffer>` into a new one. Smaller `Vec<Buffer>`s has better concat performance. **Describe the solution you'd like** <!-- A clear and concise description of what you want to happen. --> (Simple) Change the default block size to 2MB. 2MB is the default size of huge page in many systems, and I believe 2MB is a reasonable choice. The drawback is that we may waste up to 2MB of memory for small arrays, which can be fixed using the method below. (Advanced) Exponential increase until we hit 2MB. `4KB -> 8KB -> 16KB -> .. -> 512 KB -> 1MB -> 2MB -> ... -> 2MB -> 2MB` **Describe alternatives you've considered** <!-- A clear and concise description of any alternative solutions or features you've considered. --> We currently allow user to provide a block size when building the string view array. However, the implication of this block size is not straightforward and can take quite a lot of efforts to understand, and the user don't even know the default size without looking at the source code. I can expect the users of `StringViewArray` easily run into performance issues because of this non-trivial reason (like what I had run into) **Additional context** <!-- Add any other context or screenshots about the feature request here. --> -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
