pg_hdr_histogram is a PostgreSQL extension for exact-latency percentiles.

Most monitoring tools approximate percentiles from fixed buckets. pg_hdr_histogram stores a full HDR histogram as a first-class type, so p50 / p99 / p99.9 are measurements (~0.1% relative precision over 6 orders of magnitude), not estimates — and histograms merge losslessly across time windows and hosts.

  • Built on HdrHistogram_c.
  • Aggregates hdr_add and hdr_merge, parallel-safe, trusted = true.
  • Author: Vladimir Pavliv.

Source: https://github.com/vovcke/pg_hdr_histogram