Out of memory error when dumping Attachments table

I’ve asked this question on the mysql-users list, but there wasn’t any
more information than what I’ve seen on google.

The problem is that I get an error when trying to use mysqldump to get a
backup of our Attachments table (all other tables will process fine)

/usr/local/bin/mysqldump: Error 5: Out of memory (Needed 14154840 bytes)
when dumping table Attachments at row: 24285

mysql Ver 12.22 Distrib 4.0.24, for portbld-freebsd5.3 (i386)
mysqldump Ver 10.9 Distrib 4.1.12, for portbld-freebsd5.3 (i386)
and
mysqldump Ver 9.11 Distrib 4.0.24, for portbld-freebsd5.3 (i386)

There are pages in the mysql online docs about setting variables in
/boot/loader.conf to avoid the 512MB per-process limit in FreeBSD:

seisei# more /boot/loader.conf
set console=comconsole
kern.maxdsiz=“1G”

kern.dfldsiz=“751619277” # 750 MB

kern.maxssiz=“134217728” # 128MB

No change after reboot.

FreeBSD seisei.cs.myharris.net 5.3-RELEASE-p9 FreeBSD 5.3-RELEASE-p9 #0:
Wed Apr 20 13:14:54 EDT 2005
root@atarashii.inscriber.local:/usr/obj/usr/src/sys/GENERIC i386

vm.vmtotal:
System wide totals computed every five seconds: (values in kilobytes)
Processes: (RUNQ: 1 Disk Wait: 0 Page Wait: 0 Sleep: 58)
Virtual Memory: (Total: 1823K, Active 1132540K)
Real Memory: (Total: 1009492K Active 708436K)
Shared Virtual Memory: (Total: 40948K Active: 26944K)
Shared Real Memory: (Total: 37572K Active: 24768K)
Free Memory Pages: 48428K

I’m really grasping at straws here. Is there a way to back up the table
incrementally so that the smaller chunks don’t hit the memory limit?

Thanks,
Graham