On 01/17/2014 01:05 PM, Alexander Korotkov wrote:
Seems to be fixed in the attached version of patch.
Another improvement in this version: only left-most segments and further
are re-encoded. Left part of page are left untouched.
I'm looking into this now. A few quick notes:
* Even when you don't re-encode the whole page, you still WAL-log the
whole page. While correct, it'd be a pretty obvious optimization to only
WAL-log the modified part.
* When new items are appended to the end of the page so that only the
last existing compressed segment is re-encoded, and the page has to be
split, the items aren't divided 50/50 on the pages. The loop that moves
segments destined for the left page to the right won't move any
existing, untouched, segments.
! /*
! * Didn't fit uncompressed. We'll have to encode them. Check if both
! * new items and uncompressed items can be placed starting from last
! * segment of page. Then re-encode only last segment of page.
! */
! minNewItem = newItems[0];
! if (nolduncompressed == 0 &&
! ginCompareItemPointers(&olduncompressed[0], &minNewItem)
< 0)
! minNewItem = olduncompressed[0];
That looks wrong. If I'm understanding it right, it's trying to do
minNewItem = Min(newItems[0], olduncompressed[0]). The test should be
"nolduncompressed > 0 && ..."
No need to send a new patch, I'll just fix those while reviewing...
- Heikki
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