Hi all,
Please see this graph of data points extracted from autovacuum logs:
https://imgur.com/a/OCRKoDn . It's from a 9.6 instance with default params for autovacuum with the exceptions of
autovacuum_work_mem=10000 and log_autovacuum_min_duration=100.
1. How should we interpret the # tuples remain reported by the autovac logs? The source code says it's the "estimated total # of tuples" which to me means # dead + # live. But that is invalidated by the pattern here where the orange points (# tuples remain) are dramatically higher than # dead not removable (blue points) + # dead removed (green points) + # live (which never exceeded 1M during this entire interval, per count query).
2. Beginning around the first 6/19 tick, what could be causing # tuples remain to drop steeply after periods of growth when # tuples removed is 0? I confirmed there was no truncation. And what could the # tuples remain recurrent asymptote at ~22M mean?
(further context for those curious: the discontinuity at 6/23 is due to an individual autovacuum run getting stuck. After manually killing that run, the next one succeeded and you see that reporting toward the right of the graph)
Thanks!
Gabe