Re: [HACKERS] gist vacuum seaq access

2014-09-20 Thread Костя Кузнецов 
Heikki.I have idea. when i begining vacuum i must create structure like hash table. And the first action i fill this hash table.in code this look like:for( blkno = ..; all pages; blkno++) {  if(! gistPageIsLeaf(blkno)) { for( all tuples in blkno ) { hash[ blkno that is referenced by the tuple] = blkno; }  }}getting is parent of page is fast and simple( hash[page] ).But this solution is need 2 full reading of index. but Alexander says me that: this solution may be have a problem, because there is maintenance_work_mem.

Re: [HACKERS] gist vacuum seaq access

2014-09-12 Thread Heikki Linnakangas 

On 09/11/2014 12:16 PM, Костя Кузнецов wrote:

After discussion of gist seaq access in vaccum there are 2 issue:
Heikki says :
Vacuum needs to memorize the current NSN when it begins
1) how i may getting corect NSN.


The current NSN is just current WAL insert location, so 
GetXLogInsertRecPtr() will do it. Or if it's an unlogged table, 
GistGetFakeNSN().



Also i must setting F_DELETED flag on empty page and to clean parent from link
on deleted_pages
2) how i may getting parent of page fast??


No idea. The B-tree code uses the page's high key to search the tree, 
but that doesn't work too well for GiST. There is no high key on the 
page to search with, although you could use e.g. the last key you remove 
from the page for that. But a search from the root with that key might 
need to visit many pages before finding the deleted page, so it's not 
very fast.


I think you need to take a different approach. For example, leave the 
empty page in the tree in vacuum, but remember its page number. After 
vacuum has finished, make another full scan of the index, searching for 
the downlinks of all the empty pages.


- Heikki



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[HACKERS] gist vacuum seaq access

2014-09-11 Thread Костя Кузнецов 
After discussion of gist seaq access in vaccum there are 2 issue: Heikki says :Vacuum needs to memorize the current NSN when it begins1) how i may getting corect NSN. Also i must setting F_DELETED flag on empty page and to clean parent from link on deleted_pages2) how i may getting parent of page fast?? Thanks.