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Update lazy_scan_heap header comment.

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The previous comment described how things worked in PostgreSQL 8.2
and prior.
This commit is contained in:
Robert Haas 2012-04-13 08:49:59 -04:00
parent 81e3e4fd14
commit 5630eddf1e
1 changed files with 11 additions and 6 deletions
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17
src/backend/commands/vacuumlazy.c
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@ -342,13 +342,18 @@ vacuum_log_cleanup_info(Relation rel, LVRelStats *vacrelstats)
/*
* lazy_scan_heap() -- scan an open heap relation
*
* This routine sets commit status bits, builds lists of dead tuples
* and pages with free space, and calculates statistics on the number
* of live tuples in the heap. When done, or when we run low on space
* for dead-tuple TIDs, invoke vacuuming of indexes and heap.
* This routine prunes each page in the heap, which will among other
* things truncate dead tuples to dead line pointers, defragment the
* page, and set commit status bits (see heap_page_prune). It also builds
* lists of dead tuples and pages with free space, calculates statistics
* on the number of live tuples in the heap, and marks pages as
* all-visible if appropriate. When done, or when we run low on space for
* dead-tuple TIDs, invoke vacuuming of indexes and call lazy_vacuum_heap
* to reclaim dead line pointers.
*
* If there are no indexes then we just vacuum each dirty page as we
* process it, since there's no point in gathering many tuples.
* If there are no indexes then we can reclaim line pointers on the fly;
* dead line pointers need only be retained until all index pointers that
* reference them have been killed.
*/
static void
lazy_scan_heap(Relation onerel, LVRelStats *vacrelstats,