What benefit is provided by column filtering?

Question

Options

• AThe Exadata Storage Server can select rows based on column values listed in a SQL predicate
• BStorage indexes are built on columns for use in filtering
• COnly necessary columns are returned to the database server
• DColumn filtering is a marketing term, not a real benefit

• A
  7% (5)
• B
  6% (4)
• C
  84% (56)
• D
  3% (2)

Explanation

Exadata provides column filtering, also called column projection, for table scans. Only the columns requested are returned to the database server rather than all columns in a table. For example, when the following SQL is issued, only the employee_name and employee_number columns are returned from Exadata to the database kernel. SELECT employee_name, employee_number FROM employee_table; For tables with many columns, or columns containing LOBs (Large Objects), the I/O bandwidth saved can be very large. When used together, predicate and column filtering dramatically improves performance and reduces I/O bandwidth consumption. In addition, column filtering also applies to indexes, allowing for even faster query performance.

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