On Sun, Feb 2, 2025 at 5:13 PM Dmitry Koterov <dmitry.kote...@gmail.com> wrote: > > Trying to monitor perf during the initial tablesync phase (COPY) right after > CREATE SUBSCRIPTION. I noticed that the size of 17/main/base/pgsql_tmp on the > destination node grows (tens of gigabytes) as the COPY command (running > internally on the publisher) progresses. Then in the end (when its "EXPLAIN > SELECT 1 FROM tbl" on the destination shows the approximate number of rows > equals to the number of rows on the source node) it hangs for several > minutes, and then 17/main/base/pgsql_tmp empties, and the subscription > progresses. > > It seems like if I increase work_mem to several GB, then the growth of > 17/main/base/pgsql_tmp becomes less significant. > > Questions: > > 1. Are there some diagnostics commands that would allow me to figure out what > is in those tmp files? Why does the subscriber create those tmp files and not > just write directly to the data files and WAL? (The table has 2 bytea > columns, i.e. it's TOASTed for sure.) >
We do write spill files (ending with '.spill') if the changes are large. Can you please share the name of tmp files to avoid any assumptions? -- With Regards, Amit Kapila.
