Re: POC: make mxidoff 64 bits

I noticed one minor issue after I had already sent the

previous letter.

--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -1034,7 +1034,7 @@ GetNewMultiXactId(int nmembers, MultiXactOffset *offset)
    if (nextOffset + nmembers < nextOffset)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-                "MultiXact members would wrap around"));
+                errmsg("MultiXact members would wrap around")));
    *offset = nextOffset;

$ $PGBINOLD/pg_controldata -D pgdata
pg_control version number:            1800
Catalog version number:               202510221
...
Latest checkpoint's NextMultiXactId:  10000000
Latest checkpoint's NextMultiOffset:  999995050
Latest checkpoint's oldestXID:        748
...

I tried finding out how long it would take to convert a big number of
segments. Unfortunately, I only have access to a very old machine right
now. It took me 7 hours to generate this much data on my old
Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz with 16 Gb of RAM.

Here are my rough measurements:

HDD
$ sudo sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
$ time pg_upgrade
...
real    4m59.459s
user    0m19.974s
sys     0m13.640s

SSD
$ sudo sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
$ time pg_upgrade
...
real    4m52.958s
user    0m19.826s
sys     0m13.624s

I aim to get access to more modern stuff and check it all out there.