Data Mgmt Lab_Part_48 - 142 Chapter 14 Reserves relation in...

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Unformatted text preview: 142 Chapter 14 Reserves relation in memory as possibly, leaving 2 extra buffer pages (one for input pages of Sailors, the other for output pages plus enough pages for a single bit for each record of the block of R. These ’bit pages’ are initially set to zero; when a tuple of S matches a tuple in R, the bit is set to 1 meaning that this page has already met the join condition. Once all of S has been compared to the block of R, any tuple with its bit still set to zero is added to the ouput with a null value for the S tuple. This process is then repeated for the remaining blocks of R. (b) index nested loops join An index nested loops join requires an index for Sailors on all attributes that Reserves and Sailors have in common. For each tuple in Reserves, if it matches a tuple in the S index, it is added to the output, otherwise the R tuple is added to the output with a null value. (c) sort-merge join When the two relations are merged, Reserves is scanned in sorted order and if there is no match in Sailors, the Reserves tuple is added to the output with a null...
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This note was uploaded on 01/17/2012 for the course EGN 4302 taught by Professor Dr.vishak during the Fall '12 term at University of Central Florida.

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Data Mgmt Lab_Part_48 - 142 Chapter 14 Reserves relation in...

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