Hi Gabriel,
No, you can't currently modify compressed tables.
For in memory tables, are you aware of the HEAP type for non-critical
data?
You're probably talking regular permanent tables, though. For those, the
OS will use all free memory (that programs aren't using) to cache file
data after it's accessed, so you shouldn't have to worry about doing
anything special. Provided you don't have your key_buffer (or other
global vars) set too large, most of that 4.3GB database should be able
to be cached by the OS. Of course, the disk is still used for writes,
but should hardly ever need to be hit for reads.
BTW, I don't really know what memory mapped means... Surely this doesn't
mean data is kept in memory *by MySQL*?? A big compressed table would
take all your memory! Hmm.
Matt
- Original Message -
From: Gabriel Ricard
Sent: Thursday, October 09, 2003 7:09 PM
Subject: storing tables in ram / compressed myisam tables
So, we just got this handy dandy new G5 with 4GB of RAM and I'm trying
to get it to store as much of our 4.3GB database in RAM as possible.
I've tuned most of the usual parameters (query cache, tmp table size,
sort buffer, key buffer, record buffer, table cache, myisam sort
buffer, etc.) but then I was reading the section of the manual about
how mysql uses memory (http://www.mysql.com/doc/en/Memory_use.html)
and
it said this:
Only the compressed ISAM / MyISAM tables are memory mapped. This is
because the 32-bit memory space of 4 GB is not large enough for most
big tables. When systems with a 64-bit address space become more
common
we may add general support for memory mapping.
I tried to find some more information about compressed ISAM / MyISAM
tables. I found the options for CREATE TABLE to create a compressed
table, but then I was reading about myisampack and I think I got
confused. Can you still modify a compressed table? Or is it read only?
Will it be mmap'd so the access is faster? Or is this configurable? If
I could, I'd select a few of the tables to have stored in RAM to make
the access as fast as possible. Can I do this?
Also, considering that 64 bit systems like the PowerMac G5 and
Athlon64
FX boxes are readily available now, will there soon be an option to
choose whether or not a table (of any type) can be maintained in RAM
via mmap like the manual said?
TIA
- Gabriel
--
MySQL General Mailing List
For list archives: http://lists.mysql.com/mysql
To unsubscribe:http://lists.mysql.com/[EMAIL PROTECTED]
