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.
Oh, I overlooked it. I wrote code in ginRedoInsertData which finds appropriate place fro data but didn't notice that I still wrote whole page to xlog record.
* 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.
I think this loop will move one segment. However, it's too small.
! /* ! * 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 && ..."
Yes, definitely a bug.
No need to send a new patch, I'll just fix those while reviewing...