On Thu, 2025-12-18 at 13:48 -0500, Matthew Planchard wrote: > In a table with high insert frequency (~1.5k rows/s) and high query > frequency (~1k queries/s), partitioned by record creation time, we have > observed the following behavior: > > * When the current time crosses a partition boundary, all new records > are written to the new partition, which was previously empty, as > expected > > * Because the planner's latest knowledge of the partition was based on > its state prior to the cutover, it assumes the partition is empty and > creates plans that use sequential scans > > * The table accumulates tens to hundreds of thousands of rows, and the > sequentail scans start to use nearly 100% of available database CPU > > * Eventually the planner updates thee stats and all is well, but the > cycle repeats the next time the partitions cut over. > > We have tried setting up a cron job that runs ANALYZE on the most recent > partition of the table every 15 seconds at the start of the hour, and > while this does help in reducing the magnitude and duration of the > problem, it is insufficient to fully resolve it (our engineers are still > getting daily pages for high DB CPU utilization). > > We have considered maintaining a separate connection pool with > connections that have `enable_seqscan` set to `off`, and updating the > application to use that pool for these queries, but I was hoping the > community might have some better suggestions.
I would try to tune autovacuum to check more often: autovacuum_naptime = 5s # perhaps even less Then hopefully the new partitions get analyzed early enough. Yours, Laurenz Albe
