src/backend/storage/freespace/indexfsm.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * indexfsm.c
   4  *        POSTGRES free space map for quickly finding free pages in relations
   5  *
   6  *
   7  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
   8  * Portions Copyright (c) 1994, Regents of the University of California
   9  *
  10  * IDENTIFICATION
  11  *        src/backend/storage/freespace/indexfsm.c
  12  *
  13  *
  14  * NOTES:
  15  *
  16  *      This is similar to the FSM used for heap, in freespace.c, but instead
  17  *      of tracking the amount of free space on pages, we only track whether
  18  *      pages are completely free or in-use. We use the same FSM implementation
  19  *      as for heaps, using BLCKSZ - 1 to denote used pages, and 0 for unused.
  20  *
  21  *-------------------------------------------------------------------------
  22  */
  23 #include "postgres.h"
  24
  25 #include "storage/freespace.h"
  26 #include "storage/indexfsm.h"
  27
  28 /*
  29  * Exported routines
  30  */
  31
  32 /*
  33  * GetFreeIndexPage - return a free page from the FSM
  34  *
  35  * As a side effect, the page is marked as used in the FSM.
  36  */
  37 BlockNumber
  38 GetFreeIndexPage(Relation rel)
  39 {
  40         BlockNumber blkno = GetPageWithFreeSpace(rel, BLCKSZ / 2);
  41
  42         if (blkno != InvalidBlockNumber)
  43                 RecordUsedIndexPage(rel, blkno);
  44
  45         return blkno;
  46 }
  47
  48 /*
  49  * RecordFreeIndexPage - mark a page as free in the FSM
  50  */
  51 void
  52 RecordFreeIndexPage(Relation rel, BlockNumber freeBlock)
  53 {
  54         RecordPageWithFreeSpace(rel, freeBlock, BLCKSZ - 1);
  55 }
  56
  57
  58 /*
  59  * RecordUsedIndexPage - mark a page as used in the FSM
  60  */
  61 void
  62 RecordUsedIndexPage(Relation rel, BlockNumber usedBlock)
  63 {
  64         RecordPageWithFreeSpace(rel, usedBlock, 0);
  65 }
  66
  67 /*
  68  * IndexFreeSpaceMapVacuum - scan and fix any inconsistencies in the FSM
  69  */
  70 void
  71 IndexFreeSpaceMapVacuum(Relation rel)
  72 {
  73         FreeSpaceMapVacuum(rel);
  74 }