From: | Lionel Barth <lbarth(at)hachette-livre(dot)fr> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | slow update |
Date: | 1998-10-16 15:21:45 |
Message-ID: | 36276486.5BB2B057@hachette-livre.fr |
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Thread: | |
Lists: | pgsql-general |
Hello,
I use a Postgres 6.3.2 whith the btree_adj-980730 patch on a Sun
UltraSparc 1 under Solaris 2.5.1
I create a table
CREATE TABLE dlf (lft int4 NOT NULL, id varchar(20), rgt int4 NOT NULL,
niv int4, tag varchar(32), type varchar(32));
I feed the table with about 5600 tuples
COPY dlf FROM '....../dlf.import';
I create an index
CREATE INDEX dlf_lft_index on dlf using btree (lft int4_ops );
I make updates
explain update dlf set lft = lft+2 where lft>7;
Index Scan on dlf (cost=119.50 size=1870 width=54)
Why is the update so slow?
explain update dlf set lft = lft+2;
Seq Scan on dlf (cost=244.13 size=5610 width=54)
Why do I have a Seq Scan instead of an Index Scan?
vacuum dlf;
explain update dlf set lft = lft+2 where lft>7;
Index Scan on dlf (cost=151.53 size=1871 width=54)
explain update dlf set lft = lft+2;
Seq Scan on dlf (cost=244.20 size=5612 width=54)
Why are the updates slower after the vacuum?
Thank you
Lionel Barth
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