| OCR Text |
Show so <~ncl it m<tinta ius LraJJsaction information r~lat ecl to obj ect operations. T lw rest of t hP opPrations are p<~ rfo r med by the server. ESM has one disk process for each d isk volume to do 1/ 0 . T his d isk process communicates with the server v ia shared Ill emory. In Postgres, a ll operations are performed by the serve r. The server forks one procPss pPr user to ha ndle clie nt req uests . 5.3.2 Copying and translation Copy ing is necessetry in .Alphn._l hecause of object evolution . .A n attempt has he('!l made to keep the t ra nslation and copying to a minimum. Still , there are a f"ew differene<-'s in tlw POS illterfd.n's. 111 ObServer, object evoluLiou <wei poiuLe r swizz ling a re performed directly on the object copy t hat Lhe c li e nt gds fron1 tlw server. One restrict ion that SSM im poses is t hat it does not provide d irect poi nters t.o o hj f~cts. Instead, it mand ates tbat a ll references use a structure called a "user dcsn iptor." T' his al lows J::;SM to move ohjects within its buffer pool. l t is diffi cu lt to implement pointer swizzling if objects a re allowed to move. .As a resu lt , the objects ar(' copied from the ESM bufFer. The usual obj ect evolut ion and pointer swizz ling a rf' performed on this copy. In Postgres, tbf' client interacts with t he server v1a. quer1es m the form of character strings. In ord er to pass a byte-stream as a ft eld in a relation, the "null"s i11 t lw ll\rL<'-sf J'('<l.!l1 lll JJ sf IH' cscdp('rl. This lc<1ds fo Jil<tk ing llllJl t ipl<-' passes ovn Lhe hyLe-sL1·can1 a.l!d maki 11g extra. copi(~s of t h<' daLa. 5.3.3 Buffer Management lu Alpha_] , <t.ll app li cation p roceeds in distin ct p bases of loading, working, and sav lllg. .All t he data are loaded in at t he start of a session and copied b ack at |
