Postgresql hard
The 'Heap Only Tuples' (HOT) optimization improves UPDATE performance. Which specific set of conditions must be met for a HOT update to occur?
- A The update only modifies columns that are part of a GIN or GiST index, and the row is vacuumed.
- B The update does not modify any indexed columns, and space is available on the original data page.
- C The update is performed on a table with no active foreign key constraints or check conditions.
- D The update uses the `CONCURRENTLY` flag to prevent locking the table during the physical write.
Answer: B. The update does not modify any indexed columns, and space is available on the original data page.
HOT updates avoid redundant index updates. If an indexed column changes, the index must be updated to point to the new row version. If not, and the new version fits on the same page, the index points to the old row, which points to the new one.
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