Thread

Re: SSI modularity questions

Kevin Grittner <kevin.grittner@wicourts.gov> — 2011-06-28T21:33:03Z

Heikki Linnakangas  wrote:
> On 28.06.2011 20:47, Kevin Grittner wrote:
 
> Hmm, the calls in question are the ones in heapgettup() and
> heapgettup_pagemode(), which are subroutines of heap_getnext().
> heap_getnext() is only used in sequential scans, so it seems safe
> to remove those calls.
 
I haven't found anything to the contrary, if I understand correctly,
Dan found the same, and all the tests pass without them.  Here's a
patch to remove them.  This makes the recently-added
rs_relpredicatelocked boolean field unnecessary, so that's removed in
this patch, too.
 
>> I would like to add a test involving a lossy bitmap scan. How many
>> rows are normally needed to force a bitmap scan to be lossy?
> 
> The size of bitmaps is controlled by work_mem, so you can set
> work_mem very small to cause them to become lossy earlier. Off the
> top of my head I don't have any guesstimate on how many rows you
> need.
> 
>> What's the easiest way to check whether a plan is going to use (or
>> is using) a lossy bitmap scan?
> 
> Good question. There doesn't seem to be anything in the EXPLAIN
> ANALYZE output to show that, so I think you'll have to resort to
> adding some elog()s in the right places.
 
OK, thanks.
 
-Kevin