Thread: GSoC 2015 proposal: Support for microvacuum for GiST
http://www.google-melange.com/gsoc/proposal/public/google/gsoc2015/ivanitskiy_ilya/5629499534213120
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Abstract:
Currently support for microvacuum is implemented only for BTree index. But GiST index is so useful and widely used for user defined datatypes instead of btree. During index search it reads page by page. Every tuple on the page in buffer marked as "dead" if it doesn't visible for all transactions. Whenever before receiving next page we check "dead" items and mark current page as "has garbage"[1]. When the page gets full, all the killed items are removed by calling microvacuum[2].
Benefits to the PostgreSQL Community
The improvement can reduce handover time during execution VACUUM. It will be useful for high-loaded system, where PostgreSQL is used.
Quantifiable results
Reducing VACUUM run time and INSERT run time for GiST.
Project details
I'm going to implement support for microvacuum for GiST as well as it was implemented for BTree access method, just taking into account specificity of GiST.
During IndexScan we get pages from GiST index and download elected page one by one into buffer. Every item from buffering page is checked for "dead". If item really is "dead", we write item's adress in structure BTScanOpaque in function btgettuple(). Before receiving next pafe into buffer it is started _bt_killitems(), which checked "dead" tuples with function ItemPointerEquals(). If page contains at least one "dead" tuple, it's marked:
_bt_killitems() is called when we want to download next page to buffer or end of IndexScan or ReScan.
Further, when call chain is called btinsert() -> _bt_doinsert() -> _bt_findinsertloc(), if the page, which should be carried out insert, is marked by HAS_GARBAGE flag, then function _bt_vacuum_one_page() is started. It vacuum just one index page.
I'm going to realize such features for GiST index.
Project Schedule
until May 31
Solve architecture questions with help of community.
1 June – 30 June
First, approximate implementation supporting microvacuum for GiST.
I’ve got bachelor's degree in this month so I haven’t much time to work on project.
1 July – 31 July
Implementation of supporting microvacuum for GiST and testing.
1 August -15 August
Final refactoring, testing and committing.
About myself
I'm last year student at Moscow Engineering and Physical Institute at department "Cybernetics".
Links
- http://doxygen.postgresql.org/nbtutils_8c.html#a60f25ce314f5395e6f6ae44ccbae8859
- http://doxygen.postgresql.org/nbtinsert_8c.html#a89450d93d20d3d5e2d1e68849b69ee32
- https://wiki.postgresql.org/wiki/GSoC_2015#Core
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Best wishes,
On 03/26/2015 11:37 PM, Ilia Ivanicki wrote: > *Abstract:* > Currently support for microvacuum is implemented only for BTree index. But > GiST index is so useful and widely used for user defined datatypes instead > of btree. During index search it reads page by page. Every tuple on the > page in buffer marked as "dead" if it doesn't visible for all transactions. > Whenever before receiving next page we check "dead" items and mark current > page as "has garbage"[1]. When the page gets full, all the killed items are > removed by calling microvacuum[2]. Seems reasonable. Should be a pretty straightforward to implement. > *Project Schedule * > > until May 31 > > Solve architecture questions with help of community. > > 1 June – 30 June > > First, approximate implementation supporting microvacuum for GiST. > > I’ve got bachelor's degree in this month so I haven’t much time to work on > project. > > 1 July – 31 July > > Implementation of supporting microvacuum for GiST and testing. > > 1 August -15 August > > Final refactoring, testing and committing. GSoC should be treated as a full-time job, that's how much time you're expected to dedicate to it. Having bachelor's degree exams in June would be a serious problem. You'll need to discuss with the potential mentors on how to make up for that time. Other than that, the schedule seems fairly relaxed. In fact, this project seems a bit too small for a GSoC project. I'd suggest coming up with some additional GiST-related work that you could do, in addition to the microvacuum thing. Otherwise I think there's a risk that you finish the patch in May, and have nothing to do for the rest of the summer. - Heikki
GSoC should be treated as a full-time job, that's how much time you're expected to dedicate to it. Having bachelor's degree exams in June would be a serious problem. You'll need to discuss with the potential mentors on how to make up for that time.
Other than that, the schedule seems fairly relaxed. In fact, this project seems a bit too small for a GSoC project. I'd suggest coming up with some additional GiST-related work that you could do, in addition to the microvacuum thing. Otherwise I think there's a risk that you finish the patch in May, and have nothing to do for the rest of the summer.