John Arbash Meinel wrote:

How about a quick side track.
Have you played around with your shared_buffers, maintenance_work_mem,
and work_mem settings?

I have tried to set shared_buffers to 48000 now but no speedup (11,098.813 ms third try). The others are still default. I'll see documentation and will play with the other parameters.

What version of postgres are you using?


The above names changed in 8.0,
and 8.0 also has some perfomance improvements over the 7.4 series.

What is your hardware?

My dev notebook Acer TravelMate 292LMi
$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 9
model name : Intel(R) Pentium(R) M processor 1500MHz
stepping : 5
cpu MHz : 1495.485
cache size : 1024 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr mce cx8 sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 tm pbe est tm2
bogomips : 2957.31

$ cat /proc/meminfo
MemTotal:       516136 kB
MemFree:         18024 kB
Buffers:         21156 kB
Cached:         188868 kB
SwapCached:         24 kB
Active:         345596 kB
Inactive:       119344 kB
HighTotal:           0 kB
HighFree:            0 kB
LowTotal:       516136 kB
LowFree:         18024 kB
SwapTotal:     1004020 kB
SwapFree:      1003996 kB
Dirty:               4 kB
Writeback:           0 kB
Mapped:         343676 kB
Slab:            18148 kB
CommitLimit:   1262088 kB
Committed_AS:   951536 kB
PageTables:       2376 kB
VmallocTotal:   516056 kB
VmallocUsed:     90528 kB
VmallocChunk:   424912 kB

IDE disc.

# hdparm -Tt /dev/hda
Timing cached reads:   1740 MB in  2.00 seconds = 870.13 MB/sec
Timing buffered disk reads:   40 MB in  3.30 seconds =  12.10 MB/sec

Are you testing this while there is load on the
system, or under no load.

The load is low. This is few seconds after I have run the EXPLAIN ANALYZE.

# cat /proc/loadavg
0.31 0.51 0.33 1/112 6909

Are you re-running the query multiple times, and reporting the later
speeds, or just the first time? (If nothing is loaded into memory, the
first run is easily 10x slower than later ones.)

The times changes only little. First run was about 13 sec, second about 10 sec, third about 11 sec etc.

Just some background info. If you have set these to reasonable values,
we probably don't need to spend much time here, but it's just one of
those things to check.

Sure you are right. I'll try the other parameters.

John =:->

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