Function gc_string_view_batch

fn gc_string_view_batch(batch: &RecordBatch) -> RecordBatch

Heuristically compact StringViewArrays to reduce memory usage, if needed

Decides when to consolidate the StringView into a new buffer to reduce memory usage and improve string locality for better performance.

This differs from StringViewArray::gc because:

1. It may not compact the array depending on a heuristic.
2. It uses a precise block size to reduce the number of buffers to track.

Heuristic

If the average size of each view is larger than 32 bytes, we compact the array.

StringViewArray include pointers to buffer that hold the underlying data. One of the great benefits of StringViewArray is that many operations (e.g., filter) can be done without copying the underlying data.

However, after a while (e.g., after FilterExec or HashJoinExec) the StringViewArray may only refer to a small portion of the buffer, significantly increasing memory usage.