greenplumn itemptr 源码
greenplumn itemptr 代码
文件路径：/src/backend/storage/page/itemptr.c
/*-------------------------------------------------------------------------
*
* itemptr.c
* POSTGRES disk item pointer code.
*
* Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/storage/page/itemptr.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "storage/itemptr.h"
/*
* ItemPointerEquals
* Returns true if both item pointers point to the same item,
* otherwise returns false.
*
* Note:
* Asserts that the disk item pointers are both valid!
*/
bool
ItemPointerEquals(ItemPointer pointer1, ItemPointer pointer2)
{
/*
* We really want ItemPointerData to be exactly 6 bytes. This is rather a
* random place to check, but there is no better place.
*/
StaticAssertStmt(sizeof(ItemPointerData) == 3 * sizeof(uint16),
"ItemPointerData struct is improperly padded");
if (ItemPointerGetBlockNumber(pointer1) ==
ItemPointerGetBlockNumber(pointer2) &&
ItemPointerGetOffsetNumber(pointer1) ==
ItemPointerGetOffsetNumber(pointer2))
return true;
else
return false;
}
/*
* ItemPointerCompare
* Generic btree-style comparison for item pointers.
*/
int32
ItemPointerCompare(ItemPointer arg1, ItemPointer arg2)
{
/*
* Use ItemPointerGet{Offset,Block}NumberNoCheck to avoid asserting
* ip_posid != 0, which may not be true for a user-supplied TID.
*/
BlockNumber b1 = ItemPointerGetBlockNumberNoCheck(arg1);
BlockNumber b2 = ItemPointerGetBlockNumberNoCheck(arg2);
if (b1 < b2)
return -1;
else if (b1 > b2)
return 1;
else if (ItemPointerGetOffsetNumberNoCheck(arg1) <
ItemPointerGetOffsetNumberNoCheck(arg2))
return -1;
else if (ItemPointerGetOffsetNumberNoCheck(arg1) >
ItemPointerGetOffsetNumberNoCheck(arg2))
return 1;
else
return 0;
}
static char *
ItemPointerToBuffer(char *buffer, ItemPointer tid)
{
// Do not assert valid ItemPointer -- it is ok if it is (0,0)...
BlockNumber blockNumber = BlockIdGetBlockNumber(&tid->ip_blkid);
OffsetNumber offsetNumber = tid->ip_posid;
sprintf(buffer,
"(%u,%u)",
blockNumber,
offsetNumber);
return buffer;
}
static char itemPointerBuffer[50];
static char itemPointerBuffer2[50];
char *
ItemPointerToString(ItemPointer tid)
{
return ItemPointerToBuffer(itemPointerBuffer, tid);
}
char *
ItemPointerToString2(ItemPointer tid)
{
return ItemPointerToBuffer(itemPointerBuffer2, tid);
}
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