G heap le aribute name and type for each aribute index

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Unformatted text preview: Systems 3ed , R. Ramakrishnan and J. Gehrke 24 System Catalogs (will revisit in DavisDB, Part 3) •  For each index: –  structure (e.g., B+ ­tree) and search key fields •  For each rela6on –  name, file name, file structure (e.g., heap file) –  a[ribute name and type, for each a[ribute –  index name, for each index –  integrity constraints •  For each view: –  view name and defini6on •  Plus sta6s6cs, authoriza6on, buffer pool size, etc –  Catalogs are themselves stored as rela1ons! AEtr_Cat(aSystem matalog Table ,for pe, position) t xample: ttr_na C e, rel_name ty A[ributes attr_name attr_name rel_name type position sid name login age gpa fid fname sal rel_name Attribute_Cat Attribute_Cat Attribute_Cat Attribute_Cat Students Students Students Students Students Faculty Faculty Faculty type string string string integer string string string integer real string string real abase Management Systems 3ed , R. Ramakrishnan and J. Gehrke position 1 2 3 4 1 2 3 4 5 1 2 3 26 Summary •  Disks provide cheap, non ­vola6le, but slow storage –  Random access, but cost depends on loca6on of page on disk; important to arrange data sequen6ally to minimize seek delays •  DavisDB isn't very smart about this •  Buffer manager brings pages into RAM –  Page stays in RAM un6l released by requestor –  Wri[en to disk when frame chosen for replacement (which is some 6me ajer requestor releases the page) –  Choice of frame to replace based on replacement policy –  Tries to pre ­fetch several pages at a 6me •  DavisDB doesn't worry about this Summary (Con6nued) •  File layer keeps track of pages in a file, and supports abstrac6on of a collec6on of records. –  Pages with free space iden6fied using linked list or directory structure (similar to how pages in file are kept track of) •  Indexes support efficient retrieval of records based on the values in some fields •  Catalog rela6ons store informa6on about rela6ons, indices, and views. (Informa1on that is common to all records in a given collec1on.) File and Buffer Management in DavisDB...
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