Thread: Dynamic Partial Index
Hello
I'm interesting in a partial index for a rows that aren't older than 6
mounts, something like the sentence below:
--------------------------------------------------------------------------------------------------------------------------------------------------
/CREATE INDEX name_for_the_index ON table (the_column_of_type_date)
WHERE ( the_column_of_type_date > (current_date - interval '6
month')::date );/
--------------------------------------------------------------------------------------------------------------------------------------------------
But this is not posible, I receive the next error:
--------------------------------------------------------------------------------------------------------------------------------------------------
ERROR: functions in index predicate must be marked IMMUTABLE
--------------------------------------------------------------------------------------------------------------------------------------------------
So, what is the best solution for my problem?
Thank you,
Gustavo
On Thu, 2006-08-17 at 20:50 +0300, gustavo halperin wrote:
> I'm interesting in a partial index for a rows that aren't older than 6
> mounts, something like the sentence below:
>
--------------------------------------------------------------------------------------------------------------------------------------------------
> /CREATE INDEX name_for_the_index ON table (the_column_of_type_date)
>
> WHERE ( the_column_of_type_date > (current_date - interval '6
> month')::date );/
>
--------------------------------------------------------------------------------------------------------------------------------------------------
> But this is not posible, I receive the next error:
>
--------------------------------------------------------------------------------------------------------------------------------------------------
> ERROR: functions in index predicate must be marked IMMUTABLE
>
--------------------------------------------------------------------------------------------------------------------------------------------------
> So, what is the best solution for my problem?
Create an index on the table, and then periodically move records into a
separate archive table.
Regards,
Jeff Davis
Jeff Davis wrote:
> On Thu, 2006-08-17 at 20:50 +0300, gustavo halperin wrote:
>
>> I'm interesting in a partial index for a rows that aren't older than 6
>> mounts, something like the sentence below:
>>
--------------------------------------------------------------------------------------------------------------------------------------------------
>> /CREATE INDEX name_for_the_index ON table (the_column_of_type_date)
>>
>> WHERE ( the_column_of_type_date > (current_date - interval '6
>> month')::date );/
>>
--------------------------------------------------------------------------------------------------------------------------------------------------
>> But this is not posible, I receive the next error:
>>
--------------------------------------------------------------------------------------------------------------------------------------------------
>> ERROR: functions in index predicate must be marked IMMUTABLE
>>
--------------------------------------------------------------------------------------------------------------------------------------------------
>> So, what is the best solution for my problem?
>>
>
> Create an index on the table, and then periodically move records into a
> separate archive table.
>
> Regards,
> Jeff Dave
Thanks, but I have a question. If the table is a BIIIIIIG table, use
your solution is still a good idea ?? What about to create a partial
INDEX for the really current date (and not using the function
current_date) and periodically dropped and created it with the current
day again and again ??
Thank you again,
Gustavo
On Fri, 2006-08-18 at 00:19 +0300, gustavo halperin wrote:
> > Create an index on the table, and then periodically move records into a
> > separate archive table.
> >
> > Regards,
> > Jeff Dave
> Thanks, but I have a question. If the table is a BIIIIIIG table, use
> your solution is still a good idea ?? What about to create a partial
> INDEX for the really current date (and not using the function
> current_date) and periodically dropped and created it with the current
> day again and again ??
>
If you continue to drop and recreate an index like that, it will need to
scan the table during the creation of the index. That will take a while
on a large table.
You might be better off just using a normal index. To search the index
only takes log(n) time. What problem are you currently having with a
normal index?
The downside of a normal index on a large table is that the index will
grow large and consume space. I think the solution is to move seldom-
accessed records to a separate archive table. That way, you don't ever
have to scan the archive table unless you do a search in the archives.
Regards,
Jeff Davis
Jeff Davis wrote:
> On Fri, 2006-08-18 at 00:19 +0300, gustavo halperin wrote:
>
>>> Create an index on the table, and then periodically move records into a
>>> separate archive table.
>>>
>>> Regards,
>>> Jeff Dave
>>>
>> Thanks, but I have a question. If the table is a BIIIIIIG table, use
>> your solution is still a good idea ?? What about to create a partial
>> INDEX for the really current date (and not using the function
>> current_date) and periodically dropped and created it with the current
>> day again and again ??
>>
>>
>
> If you continue to drop and recreate an index like that, it will need to
> scan the table during the creation of the index. That will take a while
> on a large table.
>
> You might be better off just using a normal index. To search the index
> only takes log(n) time. What problem are you currently having with a
> normal index?
>
> The downside of a normal index on a large table is that the index will
> grow large and consume space. I think the solution is to move seldom-
> accessed records to a separate archive table. That way, you don't ever
> have to scan the archive table unless you do a search in the archives.
>
> Regards,
> Jeff Davi
OK, I become totally convinced now. Thank you,
Gustavo