Been following YouTube to study about Database Hash Join. https://www.youtube.com/watch?v=J0nbgXIarhc * HASH TABLE* *Design Decision* * #1: Hash Function *→ How to map a large key space into a smaller domain. → Trade-off between being fast vs. collision rate. Design Decision *#2: Hashing Scheme* → How to handle key collisions after hashing. → Trade-off between allocating a large hash table vs. additional instructions to find/insert keys.
Now I have some idea about the Hash function, but the math part I have no idea. Hash Scheme is for handling collisions. Collision means that different input keys will have some output hash bits. The following part is about the *Chain Hashing. * > Maintain a linked list of buckets for each slot in the hash table. > Resolve collisions by placing all elements with the same hash key into the > same bucket. > → To determine whether an element is present, hash to its bucket and scan > for it. > → Insertions and deletions are generalizations of lookups. I still don't get it. Stackoverflow seems don't have good answers yet. So I come here, asking....
