"Pavan Deolasee" <[EMAIL PROTECTED]> writes:
> On 9/18/07, Tom Lane <[EMAIL PROTECTED]> wrote:
>> In a system with
>> HOT running well, the reasons to vacuum a table will be:
>> 1. Remove dead index entries.
>> 2. Remove LP_DEAD line pointers.
>> 3. Truncate off no-longer-used end pages.
>> 4. Transfer knowledge about free space into FSM.
>> Pruning cannot accomplish #1, #2, or #3, and without significant changes
>> in the FSM infrastructure it has no hope about #4 either.

> I guess we already have mechanism to remove dead index entries
> outside vacuum.

Not a trustworthy one --- unless you have a solid proposal for making it
work with bitmap indexscans, it would be foolish to design autovacuum
behavior on the assumption that dead index entries aren't a problem.

(Also, IIRC only btree has been taught to recover dead entries at all.)

                        regards, tom lane

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