Re: Stuck using Sequential Scan

On Tue, 2004-09-07 at 22:32, Jeremy M. Guthrie wrote:
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> I have a problem where I have the table format listed below. I have the
> primary key tsyslog_id and the index built against it. However, when I
> select a unique row, it will only ever do a seq scan even after I turn off
> all other types except indexscan. I understand you cannot fully turn off seq
> scan.
...
> I cannot run vacuum more than once a day because of its heavy IO penalty. I
> run analyze once an hour. However, if I run analyze then explain, I see no
> difference in the planners decisions. What am I missing?
>
>
> TSyslog=# \d syslog_tarchive;
> Table "public.syslog_tarchive"
> Column | Type |
> Modifiers
> - ------------+------------------------+-------------------------------------------------------------------------
> tsyslog_id | bigint | not null default
...
>
> TSyslog=# explain select * from tsyslog where tsyslog_id=431650835;

That constant is INTEGER, whereas the column is BIGINT; there is no
automatic conversion in this case, so the planner does not realise the
index is usable for this query (I think 8.0 solves this).

Try: select * from tsyslog where tsyslog_id=431650835::BIGINT;

--
Oliver Elphick olly(at)lfix(dot)co(dot)uk
Isle of Wight http://www.lfix.co.uk/oliver
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