Re: Indexs and prolems with.

On Wed, 6 Feb 2002, Michael McAlpine wrote:

> Here are the results and the puzzle
>
> 1) explain select * from table1 where charcol1 = 'asdfasd'
> Index Scan using idx_charcol1 on table1 (cost=0.00..5.00 rows=1 width=456)
>
> 2) explain select * from table1 where charcol1 like 'asdfa%'
> Index Scan using idx_charcol1 on table1 (cost=0.00..5.00 rows=1 width=456)
>
> 3) explain select * from table1 where charcol2 like "aefsadf%'
> Index Scan using idx_charcol2 on table1 (cost=0.00..5.00 rows=1 width=456)
>
> but when I try
>
> 4) explain select * from table1 where charcol2 = 'asdfasd'
> Seq Scan on table1 (cost=0.00..234872.84 rows=168205 width=456)
>
>
> I have the proper locale setting for like queries ("C") and have
> recreated the indexes and vacuum analyzed but cannot get the last
> query to use the index.

How many rows are in the table? It's estimating 168205 rows matching
asdfasd which could very possibly push it over to deciding on a sequence
scan.