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doc: Correct description of values used in FSM for indexes

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The implementation of FSM for indexes is simpler than heap, where 0 is
used to track if a page is in-use and (BLCKSZ - 1) if a page is free.
One comment in indexfsm.c and one description in the documentation of
pg_freespacemap were incorrect about that.

Author: Alex Friedman <alexf01@gmail.com>
Discussion: https://postgr.es/m/71eef655-c192-453f-ac45-2772fec2cb04@gmail.com
Backpatch-through: 13
This commit is contained in:
Michael Paquier 2025-03-27 10:20:41 +09:00
parent c325a7633f
commit 44fe6ceb51
2 changed files with 2 additions and 2 deletions
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2
doc/src/sgml/pgfreespacemap.sgml
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@ -67,7 +67,7 @@
<para> <para>
For indexes, what is tracked is entirely-unused pages, rather than free For indexes, what is tracked is entirely-unused pages, rather than free
space within pages. Therefore, the values are not meaningful, just space within pages. Therefore, the values are not meaningful, just
whether a page is full or empty. whether a page is in-use or empty.
</para> </para>
</sect2> </sect2>

2
src/backend/storage/freespace/indexfsm.c
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@ -16,7 +16,7 @@
* This is similar to the FSM used for heap, in freespace.c, but instead * This is similar to the FSM used for heap, in freespace.c, but instead
* of tracking the amount of free space on pages, we only track whether * of tracking the amount of free space on pages, we only track whether
* pages are completely free or in-use. We use the same FSM implementation * pages are completely free or in-use. We use the same FSM implementation
* as for heaps, using BLCKSZ - 1 to denote used pages, and 0 for unused. * as for heaps, using 0 to denote used pages, and (BLCKSZ - 1) for unused.
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */