Joins
Index Nested Loops Join
The join algorithms we've examined so far don't assume any indexes.
If a table has an index on the join columns:
- It can greatly speed up the inner loop.
- Instead of scanning the entire table for qualifying rows, use the index to find them.
If S has an index on the join columns:
for each row r in R:
for each row s in index_scan(join columns(r)):
output join(r, s)
|