BRIN is 1/4570th the size of a B-tree, until 5% of rows are updated
Summary
A DeepSQL blog post analyzing BRIN (zonemap) versus B-tree indexes in PostgreSQL. It presents benchmark data showing BRIN's extreme size advantage on fresh data, then documents how modest updates ( churn ) cause BRIN pruning to collapse dramatically, causing large increases in I/O and execution time. The article includes a reproducible harness, explains why correlation metrics can be misleading, and discusses a fix (CLUSTER followed by ANALYZE) with associated costs.