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Parents that have larger number of child tuples could

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Unformatted text preview: ng update has not been performed? (confusing) Ê༌  Write follows read Ê༌  A write on a previously read x, will be written on the same version or a newer one. Ê༌  Pending updates. 18 3 10/29/13 Query Processor? Ê༌  A layer above the record manager. Ê༌  Problems? SQL Query Processing (Johnson, 2009) Figure 1 from (Brantner et al., 2008) 19 Example SQL Query Processing Entity- Relationship Diagram SQL Query: Average age of patrons who weigh more than 150 pounds grouped by eye color. Ê༌  A variant of MapReduce with BigTable as a data structure. Ê༌  Select- group- aggregate applications. SQL query from page 19 (Johnson, 2009) Figure 1 from (Johnson, 2009) 21 22 Compute avg age Filter input by weight (color, age) Group by color Proposed Changes Ê༌  Store all data in a BigTable. Ê༌  Launch a map instance for each tablet. Ê༌  Code is small while tablets are large à༎more efficient distribution. Ê༌  Tablet is input instead of individual text lines to map functions. Ê༌  Ability to skip rows with same id (data organization is explained next). Problem: Serial Processing in Reducers 23 Figure 2 from (Johnson, 2009) Ê༌  Use of multiple reduce phases Ê༌  With the ability to bypass the system’s sort operation. 24 4 10/29/13 Data Organization Entity- Relationship Diagram Parents Ê༌  BigTable data is addressed by row id and column name...
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