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
# hdparm -Tt /dev/hda /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.
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---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match