From: | "Albert Loo" <albertsql(at)hotmail(dot)com> |
---|---|
To: | pgsql-sql(at)postgresql(dot)org |
Subject: | query to do a backward 'skip', possible with (index) optimization ? |
Date: | 2000-01-10 21:15:39 |
Message-ID: | 20000110131539.77866.qmail@hotmail.com |
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Thread: | |
Lists: | pgsql-sql |
hi,
Coming from xbase background and having just started on sql, I tried sql
queries that does xbase 'skip'. I wanted to implement record browsing with
'Next' and 'Previous' features. Currently, I'm testing this with a table of
about 20,000 rows using psql.
I'm able to perform 'forward skip' query with :
=> select * from mytable where id > '12345' order by id limit 1;
- which returned what I wanted, 1 record with id value '12346'. Indexing on
id further optimised the query.
However, I'm unable to optimise query when doing a 'backward skip'. I've
tried :
=> select * from mytable where id < '12345' order by id desc limit 1;
- which returned the correct result '12344', but without optimization.
I was hoping a descending order index key would optimise it, but I think
postgresql don't support it (yet ?).
Next, I tried using offset -1...which is not possible either :)
=> select * from mytable where id > '12345' order by id limit 1 offset -1;
ERROR: parser: parse error at or near "-"
Has anyone tried 'backward skip' with optimization ?
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