How does rehashing occur in Swiss Tables?

In Swiss Tables (used, for example, in hash table implementations in Go), the table expansion occurs by increasing the size of the bucket array and redistributing elements with new hashing.

A feature of Swiss Tables is storing metadata (such as hash checksums) alongside keys to speed up search and reduce collisions. During expansion:

1. The table size is increased, usually doubled.
2. All existing elements are rehashed into the new table considering the new size.
3. An optimized rehashing algorithm is used, minimizing operations and copying.

This allows maintaining high performance of insert and search operations even as the number of elements grows.

Here is a simplified pseudocode example of expansion:

func (t *SwissTable) resize() {
    newSize := t.size * 2
    newTable := make([]bucket, newSize)
    for _, bucket := range t.buckets {
        for _, entry := range bucket.entries {
            newIndex := hash(entry.key) % newSize
            newTable[newIndex].add(entry)
        }
    }
    t.buckets = newTable
    t.size = newSize
}