Labs

Why `LIKE '%word%'` cannot use a B-tree, and what an inverted index does instead

A million Zipfian documents in PostgreSQL: LIKE '%word%' with a B-tree, then a GIN full-text index for a rare and for the most common word.

Block-max skipping on a toy engine

Postings for 50,000 documents and 5 Zipfian terms: exhaustive top-10 scoring against block-max skipping, postings read, and where skipping stops being safe.

The memory-bound arithmetic of brute-force vector search

400,000 random 768-dimensional vectors: one brute-force query as float32, float16 and int8, effective bandwidth, and float32 scaled to 10 million vectors.

Measure recall against brute-force truth, and see the filtered-search collapse

An HNSW index over 200,000 random vectors: recall@10 and queries per second for efSearch 10 to 200; then a 0.5% filter, post-filtered and pre-filtered.

Three self-joins versus a frontier expansion

A power-law graph of a million vertices: 1- to 4-hop chained self-joins in PostgreSQL against a CSR breadth-first search, from a median vertex and from the top hub.

Supersteps and the straggler tax

10 PageRank supersteps over a power-law graph split across 8 workers by vertex and by edge, with and without a combiner; then PageRank iterations against connected components.

Filter and refine, and the fill ratio

100,000 circles and buffered diagonal lines: bounding-box false positives by fill ratio, STRtree filter-and-refine against brute force, and the raw-degree distance trap.

Cardinality wall and Gorilla encoding

Series counts with and without a user_id label; delta-of-delta and XOR encoding of a million points, regular and noisy; minute rollups of an hour's p99.