Re: Slow UPADTE, compared to INSERT

Shridhar Daithankar <shridhar_daithankar@persistent.co.in> writes:
> This is not a bug. It is just that people find it confusing when
> postgresql planner consider seemingly same type as different.

It certainly is a bug, or at least a deficiency: PostgreSQL planner
*could* use the index to process the query, but the planner doesn't
consider doing so. The fact that it isn't able to do the necessary
type coercion is the *cause* of the bug, not a defence for this
behavior.

> AFAIK, the fix in CVS is to make indexes operatable with seemingly
> compatible types. Which does not change the fact that postgresql can
> not upgrade data types on it's own.

I'm not sure what you mean by that. In any case, I just checked, and
it does seem Tom has fixed this in CVS:

template1=# create table abc (b int8);
CREATE TABLE
template1=# set enable_seqscan = false;
SET
template1=# create index abc_b_idx on abc (b);
CREATE INDEX
template1=# explain select * from abc where b = 4;
                              QUERY PLAN
----------------------------------------------------------------------
 Index Scan using abc_b_idx on abc  (cost=0.00..17.07 rows=5 width=8)
   Index Cond: (b = 4)
(2 rows)

Cool!

-Neil