pgrdf.stats() — operator observability

One UDF returns a JSONB snapshot of internal state: dictionary cache size and hit rate, prepared-plan cache size, last-run ingest stats, build metadata.

What it does

pgrdf.stats() → JSONB is the stable health surface for pgRDF. The returned shape is locked by regression test 82-stats-shape.sql, so downstream Prometheus exporters / pg_stat_statements pipelines / dashboards can rely on the key set staying stable across patch releases.

Why you'd use it

• Operators — a single SQL call surfaces internal state. Scrape it on an interval; build SLOs over the keys.
• Developers — quick sanity check during local development that the extension is wired correctly.

Example

SELECT pgrdf.stats();

{
  "version":              "0.4.0",
  "shmem_dict_cache": {
    "size_entries":   12480,
    "capacity":       65536,
    "lookups_total":  189342,
    "hits":           181004,
    "misses":         8338,
    "hit_rate":       0.9560
  },
  "plan_cache": {
    "size_entries":   24,
    "hits":           1842,
    "misses":         24
  },
  "ingest_last": {
    "triples":        48217,
    "elapsed_ms":     812.4
  }
}

Tests

• tests/regression/sql/82-stats-shape.sql — JSONB key contract.

See also

• Cache control.
• Prepared-plan cache.
• Shared-memory dictionary cache.