> > > 1st: you should not use a ramdisk for this, it will slow things down as > compared to simply having the table on disk. Scanning it the first time > when on disk will load it into the OS IO cache, after which you will get > memory speed. > absolutely....
after getting some replies, i dropped the table from ramdisk, and started to have that in the disk itself.. > > 2nd: you should expect the "SELECT COUNT(*)" to run at a maximum of about > 350 – 600 MB/s (depending on PG version and CPU speed). It is CPU speed > limited to that rate of counting rows no matter how fast your IO is. > am using 8.1 pentium duo core > > So, for your 700 MB table, you should expect a COUNT(*) to run in about > 1-2 seconds best case. This will approximate the speed at which other > queries can run against the table. > ok count(*) per say, but other queries is taking much time... ok i ll do more experimentations and i ll be back.... Very great thanks for all of your replies GUYZ..... > > - Luke > > > > On 3/25/08 1:35 AM, "sathiya psql" <[EMAIL PROTECTED]> wrote: > > Dear Friends, > I have a table with 32 lakh record in it. Table size is nearly 700 > MB, and my machine had a 1 GB + 256 MB RAM, i had created the table space in > RAM, and then created this table in this RAM. > > So now everything is in RAM, if i do a count(*) on this table it > returns 327600 in 3 seconds, why it is taking 3 seconds ????? because am > sure that no Disk I/O is happening. ( using vmstat i had confirmed, no disk > I/O is happening, swap is also not used ) > > Any Idea on this ??? > > I searched a lot in newsgroups ... can't find relevant things.... ( > because everywhere they are speaking about disk access speed, here i don't > want to worry about disk access ) > > If required i will give more information on this. > > > >
