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Postgresql update op is very very slow

From: "jay" <jackem(dot)mojx(at)alibaba-inc(dot)com>
To: <pgsql-performance(at)postgresql(dot)org>
Subject: Postgresql update op is very very slow
Date: 2008-06-25 03:12:03
Message-ID: 004b01c8d671$3dec1630$ (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
I've a table with about 34601755 rows ,when I execute 'update msg_table set
type=0;' is very very slow, cost several hours, but still not complete?

Why postgresql is so slowly? Is the PG MVCC problem? 

But I try it on Mysql, the same table and rows, it only cost about 340

Any idea for the problem?

My machine config:
	Memory 8G, 8 piece 15K disk , 2CPU(Quad-Core) AMD	
	OS: Red Hat AS4

My postgres.conf main parameter is following:

shared_buffers = 5GB                    # min 128kB or max_connections*16kB
                                        # (change requires restart)
temp_buffers = 512MB                    # min 800kB
work_mem = 400MB                                # min 64kB
maintenance_work_mem = 600MB            # min 1MB
max_fsm_pages = 262144 # 2G min max_fsm_relations*16, 6 bytes each
max_fsm_relations = 2000                # min 100, ~70 bytes each

bgwriter_delay = 20ms                   # 10-10000ms between rounds
bgwriter_lru_maxpages = 500             # 0-1000 max buffers written/round
bgwriter_lru_multiplier = 2.0           # 0-10.0 multipler on buffers 

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Subject: Re: Postgresql update op is very very slow
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