Naive Hash Join

Naive Hash Join performs an in-memory hash table build and then join.

Prerequisite: Relation $R$ can fit into memory (that is, having $R\text{ being }\le B-2\text{ pages big}$). And this often not going to be possible, so solution is Grace Hash Join.

It’s basic idea is that we read all pages of relation $R$, building an in-memory hash table, and then read in each records of $S$ to look it up in $R^{\prime }s$ table.