PostgreSQL 皿伕弘仿穴布奶玉
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Postgres GEQO 卞云仃月漆詨及撢隸綜僅

湘呿讀卅荼螫

杽中寧歹六質咥敦弇凜及丟乒伉釩旵卞勾中化及荼螫

With large join queries the computing time spent for the genetic query optimization seems to be a mere fraction of the time Postgres needs for freeing memory via routine MemoryContextFree, file backend/utils/mmgr/mcxt.c. Debugging showed that it get stucked in a loop of routine OrderedElemPop, file backend/utils/mmgr/oset.c. The same problems arise with long queries when using the normal Postgres query optimization algorithm.

釐筋昑 join 杽中寧歹六及端卞﹜唬鰻讀杽中寧歹六瘉贗祭匹銀歹木月梢遙凜棉反﹜ backend/utils/mmgr/mcxt.c 白央奶伙及 MemoryContextFree 質咥毛銀勻化 Postgres 互丟乒伉釩旵毛墊卅丹凜卞优邰午允月凜棉及 仍仁域朿 卞聊亢卅中方丹匹允﹝犯田永弘仄化心月午﹜backend/utils/mmgr/oset.c 白央奶伙及 OrderedElemPop 質咥〇及伙□皿匹凜棉互井井勻化中引仄凶﹝⑺元杽鎖反騷橘及 Postgres 杽中寧歹六瘉贗祭失伙打伉朮丞毛銀勻化贏中杽中寧歹六毛墊卅勻凶凜卞手� 戲仄引允﹝

唬鰻讀失伙打伉朮丞及由仿丟□正澀爛卞勾中化及荼螫

In file backend/optimizer/geqo/geqo_params.c, routines gimme_pool_size and gimme_number_generations, we have to find a compromise for the parameter settings to satisfy two competing demands:

backend/optimizer/geqo/geqo_params.c 白央奶伙及 gimme_pool_size 質咥午 gimme_number_generations 質咥卞云中化﹜慼及 2 勾及鍬�允月邰菲毛心凶允方丹卅由仿丟□正澀爛及藍隅鰾毛葦勾仃卅仃木壬中仃引六氏﹝

Optimality of the query plan
杽中寧歹六煌脰及瘉贗嶺
Computing time
煌遙凜棉

幫醒左□田□白伕□卞勾中化方曰方中荸瑁綺及繭菲

In file backend/optimizer/geqo/geqo_eval.c, routine geqo_joinrel_size, the present hack for MAXINT overflow is to set the Postgres integer value of rel->size to its logarithm. Modifications of Rel in backend/nodes/relation.h will surely have severe impacts on the whole Postgres implementation.

backend/optimizer/geqo/geqo_eval.c 白央奶伙及 geqo_joinrel_size 質咥卞云中化﹜ rel->size 午中丹 Postgres 幫醒襖及覆醒毛澀爛允月凶戶卞﹜ MAXINT 左□田□白伕□午中丹杽鎖毛荸瑁仄卅仃木壬中仃引六氏﹝ backend/nodes/relation.h 白央奶伙及 Rel 及庍凳反﹜割撢卞 Postgres 蟈�卞釐五仁排黍毛芨尹月仇午卞卅曰引允﹝

丟乒伉裒喲卞勾中化及荸瑁綺及繭菲

Memory exhaustion may occur with more than 10 relations involved in a query. In file backend/optimizer/geqo/geqo_eval.c, routine gimme_tree is recursively called. Maybe I forgot something to be freed correctly, but I dunno what. Of course the rel data structure of the join keeps growing and growing the more relations are packed into it. Suggestions are welcome :-(

杽中寧歹六〇卞 10 蜊動曉及伉伊□扑亦件互丐月午﹜丟乒伉毛銀中絆凶仄化仄引允仇午互丐曰引允﹝ backend/optimizer/geqo/geqo_eval.c 白央奶伙匹反 gimme_tree 質咥互瘋窖讀卞裟太請今木引允﹝云公日仁窒井毛切扎氏午釩旵仄化中卅中及分午嗶尹化中月匹允互﹜引分�抸匹五化中引六氏﹝手切欠氏 join 及 rel 犯□正厭瞻蟲反伉伊□扑亦件互丐木壬丐月幻升⻖釐仄化中五引允﹝窒井荸瑁綺互卅中匹仄斤丹井 :-(

輔嗶鳳恔

GEQ失伙打伉朮丞楮洘樹扷

The Hitch-Hiker's Guide to Evolutionary Computation, J顤g Heitk飆ter and David Beasley, InterNet resource, The Design and Implementation of the Postgres Query Optimizer, Z. Fong, University of California, Berkeley Computer Science Department, Fundamentals of Database Systems, R. Elmasri and S. Navathe, The Benjamin/Cummings Pub., Inc..

FAQ in comp.ai.genetic is available at Encore.

comp.ai.genetic及 FAQ 反 Encore 井日じ澎匹五引允﹝

File planner/Report.ps in the 'postgres-papers' distribution.

'postgres-papers' ミ幵坁〇及 planner/Report.ps 白央奶伙﹝

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Postgres GEQO 卞云仃 月漆詨及撢隸綜僅