brin_page.h

Go to the documentation of this file.

/*
 * brin_page.h
 *      Prototypes and definitions for BRIN page layouts
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *      src/include/access/brin_page.h
 *
 * NOTES
 *
 * These structs should really be private to specific BRIN files, but it's
 * useful to have them here so that they can be used by pageinspect and similar
 * tools.
 */
#ifndef BRIN_PAGE_H
#define BRIN_PAGE_H
 
#include "storage/block.h"
#include "storage/itemptr.h"
 
/*
 * Special area of BRIN pages.
 *
 * We define it in this odd way so that it always occupies the last
 * MAXALIGN-sized element of each page.
 */
typedef struct BrinSpecialSpace
{
    uint16      vector[MAXALIGN(1) / sizeof(uint16)];
} BrinSpecialSpace;
 
/*
 * Make the page type be the last half-word in the page, for consumption by
 * pg_filedump and similar utilities.  We don't really care much about the
 * position of the "flags" half-word, but it's simpler to apply a consistent
 * rule to both.
 *
 * See comments above GinPageOpaqueData.
 */
#define BrinPageType(page)      \
    (((BrinSpecialSpace *)      \
      PageGetSpecialPointer(page))->vector[MAXALIGN(1) / sizeof(uint16) - 1])
 
#define BrinPageFlags(page)     \
    (((BrinSpecialSpace *)      \
      PageGetSpecialPointer(page))->vector[MAXALIGN(1) / sizeof(uint16) - 2])
 
/* special space on all BRIN pages stores a "type" identifier */
#define     BRIN_PAGETYPE_META          0xF091
#define     BRIN_PAGETYPE_REVMAP        0xF092
#define     BRIN_PAGETYPE_REGULAR       0xF093
 
#define BRIN_IS_META_PAGE(page) (BrinPageType(page) == BRIN_PAGETYPE_META)
#define BRIN_IS_REVMAP_PAGE(page) (BrinPageType(page) == BRIN_PAGETYPE_REVMAP)
#define BRIN_IS_REGULAR_PAGE(page) (BrinPageType(page) == BRIN_PAGETYPE_REGULAR)
 
/* flags for BrinSpecialSpace */
#define     BRIN_EVACUATE_PAGE          (1 << 0)
 
 
/* Metapage definitions */
typedef struct BrinMetaPageData
{
    uint32      brinMagic;
    uint32      brinVersion;
    BlockNumber pagesPerRange;
    BlockNumber lastRevmapPage;
} BrinMetaPageData;
 
#define BRIN_CURRENT_VERSION        1
#define BRIN_META_MAGIC         0xA8109CFA
 
#define BRIN_METAPAGE_BLKNO     0
 
/* Definitions for revmap pages */
typedef struct RevmapContents
{
    /*
     * This array will fill all available space on the page.  It should be
     * declared [FLEXIBLE_ARRAY_MEMBER], but for some reason you can't do that
     * in an otherwise-empty struct.
     */
    ItemPointerData rm_tids[1];
} RevmapContents;
 
#define REVMAP_CONTENT_SIZE \
    (BLCKSZ - MAXALIGN(SizeOfPageHeaderData) - \
     offsetof(RevmapContents, rm_tids) - \
     MAXALIGN(sizeof(BrinSpecialSpace)))
/* max num of items in the array */
#define REVMAP_PAGE_MAXITEMS \
    (REVMAP_CONTENT_SIZE / sizeof(ItemPointerData))
 
#endif                          /* BRIN_PAGE_H */