On 01/17/2014 08:49 PM, Alexander Korotkov wrote:
On Fri, Jan 17, 2014 at 10:38 PM, Heikki Linnakangas < hlinnakan...@vmware.com> wrote: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.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.
Yeah. I think ginRedoInsertData was too cute to be bug-free. I added an explicit unmodifiedsize field to the WAL record, so that ginRedoInsertData doesn't need to calculate it.
* 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.
Implemented this.I noticed that the gin vacuum redo routine is dead code, except for the data-leaf page handling, because we never remove entries or internal nodes (page deletion is a separate wal record type). And the data-leaf case is functionally equivalent to heap newpage records. I removed the dead code and made it more clear that it resembles heap newpage.
Attached is a yet another version, with more bugs fixed and more comments added and updated. I would appreciate some heavy-testing of this patch now. If you could re-run the tests you've been using, that could be great. I've tested the WAL replay by replicating GIN operations over streaming replication. That doesn't guarantee it's correct, but it's a good smoke test.
- Heikki
gin-packed-postinglists-20140120.patch.gz
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