On 09/14/2016 07:57 PM, Tom Lane wrote:
> Pavan Deolasee <pavan.deolasee@gmail.com> writes:
>> On Wed, Sep 14, 2016 at 10:53 PM, Alvaro Herrera <alvherre@2ndquadrant.com>
>> wrote:
>>> One thing not quite clear to me is how do we create the bitmap
>>> representation starting from the array representation in midflight
>>> without using twice as much memory transiently. Are we going to write
>>> the array to a temp file, free the array memory, then fill the bitmap by
>>> reading the array from disk?
>
>> We could do that.
>
> People who are vacuuming because they are out of disk space will be very
> very unhappy with that solution.
The people are usually running out of space for data, while these files
would be temporary files placed wherever temp_tablespaces points to. I'd
argue if this is a source of problems, the people are already in deep
trouble due to sorts, CREATE INDEX, ... as those commands may also
generate a lot of temporary files.
regards
Tomas
