src/include/access/brin_page.h

   1 /*
   2  * brin_page.h
   3  *              Prototypes and definitions for BRIN page layouts
   4  *
   5  * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
   6  * Portions Copyright (c) 1994, Regents of the University of California
   7  *
   8  * IDENTIFICATION
   9  *              src/include/access/brin_page.h
  10  *
  11  * NOTES
  12  *
  13  * These structs should really be private to specific BRIN files, but it's
  14  * useful to have them here so that they can be used by pageinspect and similar
  15  * tools.
  16  */
  17 #ifndef BRIN_PAGE_H
  18 #define BRIN_PAGE_H
  19
  20 #include "storage/block.h"
  21 #include "storage/itemptr.h"
  22
  23 /*
  24  * Special area of BRIN pages.
  25  *
  26  * We define it in this odd way so that it always occupies the last
  27  * MAXALIGN-sized element of each page.
  28  */
  29 typedef struct BrinSpecialSpace
  30 {
  31         uint16          vector[MAXALIGN(1) / sizeof(uint16)];
  32 } BrinSpecialSpace;
  33
  34 /*
  35  * Make the page type be the last half-word in the page, for consumption by
  36  * pg_filedump and similar utilities.  We don't really care much about the
  37  * position of the "flags" half-word, but it's simpler to apply a consistent
  38  * rule to both.
  39  *
  40  * See comments above GinPageOpaqueData.
  41  */
  42 #define BrinPageType(page)              \
  43         (((BrinSpecialSpace *)          \
  44           PageGetSpecialPointer(page))->vector[MAXALIGN(1) / sizeof(uint16) - 1])
  45
  46 #define BrinPageFlags(page)             \
  47         (((BrinSpecialSpace *)          \
  48           PageGetSpecialPointer(page))->vector[MAXALIGN(1) / sizeof(uint16) - 2])
  49
  50 /* special space on all BRIN pages stores a "type" identifier */
  51 #define         BRIN_PAGETYPE_META                      0xF091
  52 #define         BRIN_PAGETYPE_REVMAP            0xF092
  53 #define         BRIN_PAGETYPE_REGULAR           0xF093
  54
  55 #define BRIN_IS_META_PAGE(page) (BrinPageType(page) == BRIN_PAGETYPE_META)
  56 #define BRIN_IS_REVMAP_PAGE(page) (BrinPageType(page) == BRIN_PAGETYPE_REVMAP)
  57 #define BRIN_IS_REGULAR_PAGE(page) (BrinPageType(page) == BRIN_PAGETYPE_REGULAR)
  58
  59 /* flags for BrinSpecialSpace */
  60 #define         BRIN_EVACUATE_PAGE                      (1 << 0)
  61
  62
  63 /* Metapage definitions */
  64 typedef struct BrinMetaPageData
  65 {
  66         uint32          brinMagic;
  67         uint32          brinVersion;
  68         BlockNumber pagesPerRange;
  69         BlockNumber lastRevmapPage;
  70 } BrinMetaPageData;
  71
  72 #define BRIN_CURRENT_VERSION            1
  73 #define BRIN_META_MAGIC                 0xA8109CFA
  74
  75 #define BRIN_METAPAGE_BLKNO             0
  76
  77 /* Definitions for revmap pages */
  78 typedef struct RevmapContents
  79 {
  80         /*
  81          * This array will fill all available space on the page.  It should be
  82          * declared [FLEXIBLE_ARRAY_MEMBER], but for some reason you can't do that
  83          * in an otherwise-empty struct.
  84          */
  85         ItemPointerData rm_tids[1];
  86 } RevmapContents;
  87
  88 #define REVMAP_CONTENT_SIZE \
  89         (BLCKSZ - MAXALIGN(SizeOfPageHeaderData) - \
  90          offsetof(RevmapContents, rm_tids) - \
  91          MAXALIGN(sizeof(BrinSpecialSpace)))
  92 /* max num of items in the array */
  93 #define REVMAP_PAGE_MAXITEMS \
  94         (REVMAP_CONTENT_SIZE / sizeof(ItemPointerData))
  95
  96 #endif                                                  /* BRIN_PAGE_H */