Mnesia tables: load times and sizes after deletion

Ulf Wiger (ÄL2/EAB) ulf.wiger@REDACTED
Thu Aug 14 14:46:00 CEST 2003

Are you sure the tables were created under R9B?
If so, are you sure they are dets files (.DAT when using 

Granted, I've been on a long vacation and my brain may not
have engaged fully yet, but I recall that disc_copies are
stored on disk in disk_log format (mnesia gives them the 
extension .DCD), and not as dets files. Disc_only copies
are stored as dets files.

The file size should adjust at every log dump,
and a load time of minutes seems a bit slow, perhaps, but
I wouldn't want to swear that it's abnormal.


-----Original Message-----
From: Bruce Fitzsimons [mailto:Bruce@REDACTED]
Sent: Thursday, August 14, 2003 14:07
To: erlang-questions@REDACTED
Subject: Mnesia tables: load times and sizes after deletion


I've just been playing with my little jukebox I wrote for broadcasting
background music in Erlang. It logs the songs played into an mnesia table
'playlog' (set, disc_copies).

I managed to get 71,000 entries into the table, at which point it took a
number of minutes to open on my little Duron 1300 w/ ATA100 hd

I used a (inefficient) mnemosyne query to get all the entries older than 1
day and delete them, and this worked. Surprisingly fast, to mnemosynes

What did surprise me is that the on-disk size, and the size reported by
mnesia:table_info(playlog, size) continued to increased (it was still

Is this normal? The docs say size = total number of records, is it actually
max size? Even after the delete and normal shutdown the table did not shrink
in either sense. It still took a number of minutes to open too.

I guess I'm just curious to know if this is normal?

I attempted to directly open the mnesia files under dets to query them...but
that is apparently not allowed. A good thing probably.

Thanks for any info. I've deleted and recreated the table now. This is all
under R9C (nice work guys, great docs), although the DB was created using


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