| OCR Text |
Show 66 I L is one of tbe pcrf(mnance bottlenecks. For large objects, the creation time for CSI\Il is very high . The reason is t hat ESM builds an index on top of a ll objects wb icb are la rger than a disk page, i. e., 4EB. T his is good for random byte insertion and delet ion in the object but entai Is added overh ead at object creation time. For J>oslgn's. tlwre is a marked change at 8!\B. This is because the Postgres large object inLe r Fa.ce is used in stead of tuples to sto re large objects. F'ig11re .5 .12 shows Uw t ime ta kf~n to load objects in d. local settiug. Load time for 11ostgres is worse than t he other two for a single object with a varying object size. Oil<' rcasou kn this diff'(' r<' JJ( <' is t! Jd,L Jlustg r<'S tiS<-'S dechntt.ivf' Cjll ('ri('S 1,() aCC('SS dll oJ,jed. T' ltis nwa11S LIJal tbe qtwry must jWrcolate t lt rougb various stages like iiiri<'x lmtn agement, access path sel ection, qm~ ry op timi zation et c. , whereas oth<~rs geL an obje~ cL IJased 011 tlw object's OlD . Por la rge obj ects, more work is involved i11 PosLgres . .After gett ing the right tl tple and ext racting the file name, the file bas to he r('tri Pved separatdy. F' igure 5. 13 shows Lhe t ime taken to update objects in a local sett in g. ESl\11 does not j.wd'urlll as well as for create and load when compared to ObServer for a single uhjccL with a varying object size. One reason is that ObServer uses a redo-only ndsl1 r<'covery c;dwme w h<~ l· ea.s C~M emp loys normal log-based recovery, i. e., both r<'d o <til cl un cl o. 5 .5.1.3 C reate vs. Load vs. Update in remote case Tl1i s Lest IS sanw as th e prev ious one excep t th e cl ient a nd the server a re on sepa rate mach ines. Vigm(' .'1 .1 4 . .') . I:), <LJI<i .'l . I() sl1ow t h(' cl<tpsed time for CTf'a.tc, loacl an cl lljlliatf' 111 <t r<'mote settiug. T he graphs here mirror tbc~ same hebavior as in local sett ing. Til(' pnf'onnauce impnwcme nL dti f' to cli ent-server p<Lra llcli sm in ESI\11 is ev ident in t.lwse grapl1s, ('specially for load . |
