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This new counter, called "wal_fpi_bytes", tracks the total amount in bytes of full page images (FPIs) generated in WAL. This data becomes available globally via pg_stat_wal, and for backend statistics via pg_stat_get_backend_wal(). Previously, this information could only be retrieved with pg_waldump or pg_walinspect, which may not be available depending on the environment, and are expensive to execute. It offers hints about how much FPIs impact the WAL generated, which could be a large percentage for some workloads, as well as the effects of wal_compression or page holes. Bump catalog version. Bump PGSTAT_FILE_FORMAT_ID, due to the addition of wal_fpi_bytes in PgStat_WalCounters. Author: Shinya Kato <shinya11.kato@gmail.com> Reviewed-by: Michael Paquier <michael@paquier.xyz> Discussion: https://postgr.es/m/CAOzEurQtZEAfg6P0kU3Wa-f9BWQOi0RzJEMPN56wNTOmJLmfaQ@mail.gmail.com