| OCR Text |
Show 44 t llf' objects that contain t he objects ' and heade rs' di rectories. Each handle object contains t he namP of Alpha,_l fijp it r<-' pr t~SP n ts. 4 .5. 2 L oad The "A lpha_l " data bas <~ is opened and a t ransaction is init iated. All database ha nd les are fetched and the one whi ch corresponds to the Alpha_l file that is being loaded is se lected. It contains t he uicl of t he header a nd object directories, These <m-' f't>tc lwcl <tncl a ll headers and ubi< '<Ls a t·e loaded . 4.5.3 Update l l pciatP is very n1 uclt li k<-~ c reate except that new uicls do not have to be req uested. Only the co ntents of the objects a re updated . 4.6 Interface to Postgres t-\11 ;\ \p ha_l files d.!C' :-;to red in one Postg res database using t h rer~ relat ions. aLfi l e: ( aLname, aLf il e _info ) aLheader : ( aLname, tag, header ) aLobj ect : ( aLname, ob j _index , lo , obj ect , obj _file) aLname is the name of Alpha_] fi le, aLfil e_info contains machine characteristi cs, tag keeps t he tag numbe r of the hca.cl e r, header contains t he object descriptor, ObJ _indeX is t\lP internal () f]) , lo is II S('d to rJag a la rgP o hjr~ct , object contains Jlw h_v L< ' str<'dll l r('prC'sen t i11g t he Alpha_! ohject. a ncl obj _fil e co11ta ins t lw name or the i<trge ohject file repre:-;enting Alpb a_ l object if lo is t rue. /\lph a _l \storage management is mapp<~d on Postgres as follows: • A field in a ll relat ions ho lds the name of t he Alp ba _l fi le. To ob tain a ll tuples of a particu la r Alpha_ I Fil<'. a joi n on t his fi eld is performed. • T lw re la t iutJ aLfi l e keeps all control informatio n. |
