1/*-------------------------------------------------------------------------
4 * POSTGRES disk block definitions.
7 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
8 * Portions Copyright (c) 1994, Regents of the University of California
10 * src/include/storage/block.h
12 *-------------------------------------------------------------------------
20 * each data file (heap or index) is divided into postgres disk blocks
21 * (which may be thought of as the unit of i/o -- a postgres buffer
22 * contains exactly one disk block). the blocks are numbered
23 * sequentially, 0 to 0xFFFFFFFE.
25 * InvalidBlockNumber is the same thing as P_NEW in bufmgr.h.
27 * the access methods, the buffer manager and the storage manager are
28 * more or less the only pieces of code that should be accessing disk
33 #define InvalidBlockNumber ((BlockNumber) 0xFFFFFFFF)
35 #define MaxBlockNumber ((BlockNumber) 0xFFFFFFFE)
40 * this is a storage type for BlockNumber. in other words, this type
41 * is used for on-disk structures (e.g., in HeapTupleData) whereas
42 * BlockNumber is the type on which calculations are performed (e.g.,
43 * in access method code).
45 * there doesn't appear to be any reason to have separate types except
46 * for the fact that BlockIds can be SHORTALIGN'd (and therefore any
47 * structures that contains them, such as ItemPointerData, can also be
48 * SHORTALIGN'd). this is an important consideration for reducing the
49 * space requirements of the line pointer (ItemIdData) array on each
50 * page and the header of each heap or index tuple, so it doesn't seem
51 * wise to change this without good reason.
68 * True iff blockNumber is valid.
78 * Sets a block identifier to the specified value.
83 blockId->
bi_hi = blockNumber >> 16;
84 blockId->
bi_lo = blockNumber & 0xffff;
89 * Check for block number equality.
99 * BlockIdGetBlockNumber
100 * Retrieve the block number from a block identifier.
static bool BlockIdEquals(const BlockIdData *blockId1, const BlockIdData *blockId2)
struct BlockIdData BlockIdData
#define InvalidBlockNumber
static void BlockIdSet(BlockIdData *blockId, BlockNumber blockNumber)
static bool BlockNumberIsValid(BlockNumber blockNumber)
static BlockNumber BlockIdGetBlockNumber(const BlockIdData *blockId)