Hello pgsql-hackers, Submitting a patch that would enable gathering of per-statement WAL generation statistics, similar to how it is done for buffer usage. Collected is the number of records added to WAL and number of WAL bytes written.
The data collected was found valuable to analyze update-heavy load, with WAL generation being the bottleneck. The usage data is collected at low level, after compression is done on WAL record. Data is then exposed via pg_stat_statements, could also be used in EXPLAIN ANALYZE if needed. Instrumentation is alike to the one used for buffer stats. I didn't dare to unify both usage metric sets into single struct, nor rework the way both are passed to parallel workers. Performance impact is (supposed to be) very low, essentially adding two int operations and memory access on WAL record insert. Additional efforts to allocate shmem chunk for parallel workers. Parallel workers shmem usage is increased to fir in a struct of two longs. Patch is separated in two parts: core changes and pg_stat_statements additions. Essentially the extension has its schema updated to allow two more fields, docs updated to reflect the change. Patch is prepared against master branch. Please provide your comments and/or code findings.
wal_stats.ext.patch
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wal_stats.core.patch
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