SQL Query Optimizer

Implemented a cost-based query optimizer using dynamic programming to find optimal execution plans from exponential search space. Built statistics collector with histograms for cardinality estimation and join order selection. Achieves 100x improvement on complex queries by optimizing join ordering and index selection, reducing query time from 5 seconds to 50 milliseconds.

The optimizer uses bottom-up dynamic programming to explore join orderings efficiently. By pruning suboptimal plans early, it finds near-optimal solutions in practical time. Cardinality estimation uses column statistics and histograms to predict intermediate result set sizes.