From the objective of OSS-DB Exam Gold
- Performance Tuning - Parameters related to performance
Sample Question
3.05
Select two accurate statements regarding indexing.
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If FILLFACTOR is omitted, the target table's FILLFACTOR is used as the default value.
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If the UNLOGGED parameter is specified, WAL logging is skipped during index updates, which speeds up the update process.
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If the PARALLEL parameter is specified, multiple processes may be used to create the index, reducing creation time.
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If the CONCURRENTLY parameter is specified, the index is created without locking writes to the target table, but the creation process takes longer than a standard index build.
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Functions and operators used in index definitions must be immutable.
※This sample exam is different from those that appear in the actual OSS-DB Exam.
2025/06/02
Answer and Explanation
[Option A]
When FILLFACTOR is omitted during indexing, the default value is 90, which does not mean that the value of the target table is inherited.
Therefore, A is not accurate.
Also, if FILLFACTOR is omitted when creating a table, the default value is 100.
[Option B]
The UNLOGGED parameter can be specified at the time of table creation, but not at the time of index creation.
Therefore, B is not accurate.
Indexes created on tables created with the UNLOGGED parameter similarly do not generate WAL logs during updates.
[Option C]
There is no PARALLEL parameter, and a single index cannot be created by multiple processes.
Therefore, C is not accurate.
[Options D and E]
Both are accurate.
Refer to the following official document for details.
https://www.postgresql.org/docs/10/sql-createindex.html
The correct answers are D and E.