On 4 August 2016 at 18:27, Bruce Momjian <bruce@momjian.us> wrote:
>> > Also, why not use this bitmap for all indexes, not just update chains?
>>
>> I don't understand where you get this update chains thing from.
>>
>> The bitmap can apply to multiple tuples on one page, which is described.
>
> I am asking if we could use this idea for all rows on a page, not just
> HOT updated, e.g. we have five rows that have col1=4 in an index --- why
> not just use on index pointer for all of them, with a bitmap to point to
> the possible matches?
Yes. I described that...
"The same situation can occur if we have many INSERTs with same values
on the same block. This could lead to a reduction in size of the btree
for indexes with many duplicate values."
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
