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/*-------------------------------------------------------------------------
*
* heap_surgery.c
* Functions to perform surgery on the damaged heap table.
*
* Copyright (c) 2020-2022, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/pg_surgery/heap_surgery.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "access/visibilitymap.h"
#include "access/xloginsert.h"
#include "catalog/pg_am_d.h"
#include "catalog/pg_proc_d.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "utils/acl.h"
#include "utils/rel.h"
PG_MODULE_MAGIC;
/* Options to forcefully change the state of a heap tuple. */
typedef enum HeapTupleForceOption
{
HEAP_FORCE_KILL,
HEAP_FORCE_FREEZE
} HeapTupleForceOption;
PG_FUNCTION_INFO_V1(heap_force_kill);
PG_FUNCTION_INFO_V1(heap_force_freeze);
static int32 tidcmp(const void *a, const void *b);
static Datum heap_force_common(FunctionCallInfo fcinfo,
HeapTupleForceOption heap_force_opt);
static void sanity_check_tid_array(ArrayType *ta, int *ntids);
static BlockNumber find_tids_one_page(ItemPointer tids, int ntids,
OffsetNumber *next_start_ptr);
/*-------------------------------------------------------------------------
* heap_force_kill()
*
* Force kill the tuple(s) pointed to by the item pointer(s) stored in the
* given TID array.
*
* Usage: SELECT heap_force_kill(regclass, tid[]);
*-------------------------------------------------------------------------
*/
Datum
heap_force_kill(PG_FUNCTION_ARGS)
{
PG_RETURN_DATUM(heap_force_common(fcinfo, HEAP_FORCE_KILL));
}
/*-------------------------------------------------------------------------
* heap_force_freeze()
*
* Force freeze the tuple(s) pointed to by the item pointer(s) stored in the
* given TID array.
*
* Usage: SELECT heap_force_freeze(regclass, tid[]);
*-------------------------------------------------------------------------
*/
Datum
heap_force_freeze(PG_FUNCTION_ARGS)
{
PG_RETURN_DATUM(heap_force_common(fcinfo, HEAP_FORCE_FREEZE));
}
/*-------------------------------------------------------------------------
* heap_force_common()
*
* Common code for heap_force_kill and heap_force_freeze
*-------------------------------------------------------------------------
*/
static Datum
heap_force_common(FunctionCallInfo fcinfo, HeapTupleForceOption heap_force_opt)
{
Oid relid = PG_GETARG_OID(0);
ArrayType *ta = PG_GETARG_ARRAYTYPE_P_COPY(1);
ItemPointer tids;
int ntids,
nblocks;
Relation rel;
OffsetNumber curr_start_ptr,
next_start_ptr;
bool include_this_tid[MaxHeapTuplesPerPage];
if (RecoveryInProgress())
ereport(ERROR,
(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
errmsg("recovery is in progress"),
errhint("heap surgery functions cannot be executed during recovery.")));
/* Check inputs. */
sanity_check_tid_array(ta, &ntids);
rel = relation_open(relid, RowExclusiveLock);
/*
* Check target relation.
*/
if (!RELKIND_HAS_TABLE_AM(rel->rd_rel->relkind))
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("cannot operate on relation \"%s\"",
RelationGetRelationName(rel)),
errdetail_relkind_not_supported(rel->rd_rel->relkind)));
if (rel->rd_rel->relam != HEAP_TABLE_AM_OID)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("only heap AM is supported")));
/* Must be owner of the table or superuser. */
if (!pg_class_ownercheck(RelationGetRelid(rel), GetUserId()))
aclcheck_error(ACLCHECK_NOT_OWNER,
get_relkind_objtype(rel->rd_rel->relkind),
RelationGetRelationName(rel));
tids = ((ItemPointer) ARR_DATA_PTR(ta));
/*
* If there is more than one TID in the array, sort them so that we can
* easily fetch all the TIDs belonging to one particular page from the
* array.
*/
if (ntids > 1)
qsort((void *) tids, ntids, sizeof(ItemPointerData), tidcmp);
curr_start_ptr = next_start_ptr = 0;
nblocks = RelationGetNumberOfBlocks(rel);
/*
* Loop, performing the necessary actions for each block.
*/
while (next_start_ptr != ntids)
{
Buffer buf;
Buffer vmbuf = InvalidBuffer;
Page page;
BlockNumber blkno;
OffsetNumber curoff;
OffsetNumber maxoffset;
int i;
bool did_modify_page = false;
bool did_modify_vm = false;
CHECK_FOR_INTERRUPTS();
/*
* Find all the TIDs belonging to one particular page starting from
* next_start_ptr and process them one by one.
*/
blkno = find_tids_one_page(tids, ntids, &next_start_ptr);
/* Check whether the block number is valid. */
if (blkno >= nblocks)
{
/* Update the current_start_ptr before moving to the next page. */
curr_start_ptr = next_start_ptr;
ereport(NOTICE,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("skipping block %u for relation \"%s\" because the block number is out of range",
blkno, RelationGetRelationName(rel))));
continue;
}
buf = ReadBuffer(rel, blkno);
LockBufferForCleanup(buf);
page = BufferGetPage(buf);
maxoffset = PageGetMaxOffsetNumber(page);
/*
* Figure out which TIDs we are going to process and which ones we are
* going to skip.
*/
memset(include_this_tid, 0, sizeof(include_this_tid));
for (i = curr_start_ptr; i < next_start_ptr; i++)
{
OffsetNumber offno = ItemPointerGetOffsetNumberNoCheck(&tids[i]);
ItemId itemid;
/* Check whether the offset number is valid. */
if (offno == InvalidOffsetNumber || offno > maxoffset)
{
ereport(NOTICE,
errmsg("skipping tid (%u, %u) for relation \"%s\" because the item number is out of range",
blkno, offno, RelationGetRelationName(rel)));
continue;
}
itemid = PageGetItemId(page, offno);
/* Only accept an item ID that is used. */
if (ItemIdIsRedirected(itemid))
{
ereport(NOTICE,
errmsg("skipping tid (%u, %u) for relation \"%s\" because it redirects to item %u",
blkno, offno, RelationGetRelationName(rel),
ItemIdGetRedirect(itemid)));
continue;
}
else if (ItemIdIsDead(itemid))
{
ereport(NOTICE,
(errmsg("skipping tid (%u, %u) for relation \"%s\" because it is marked dead",
blkno, offno, RelationGetRelationName(rel))));
continue;
}
else if (!ItemIdIsUsed(itemid))
{
ereport(NOTICE,
(errmsg("skipping tid (%u, %u) for relation \"%s\" because it is marked unused",
blkno, offno, RelationGetRelationName(rel))));
continue;
}
/* Mark it for processing. */
Assert(offno < MaxHeapTuplesPerPage);
include_this_tid[offno] = true;
}
/*
* Before entering the critical section, pin the visibility map page
* if it appears to be necessary.
*/
if (heap_force_opt == HEAP_FORCE_KILL && PageIsAllVisible(page))
visibilitymap_pin(rel, blkno, &vmbuf);
/* No ereport(ERROR) from here until all the changes are logged. */
START_CRIT_SECTION();
for (curoff = FirstOffsetNumber; curoff <= maxoffset;
curoff = OffsetNumberNext(curoff))
{
ItemId itemid;
if (!include_this_tid[curoff])
continue;
itemid = PageGetItemId(page, curoff);
Assert(ItemIdIsNormal(itemid));
did_modify_page = true;
if (heap_force_opt == HEAP_FORCE_KILL)
{
ItemIdSetDead(itemid);
/*
* If the page is marked all-visible, we must clear
* PD_ALL_VISIBLE flag on the page header and an all-visible
* bit on the visibility map corresponding to the page.
*/
if (PageIsAllVisible(page))
{
PageClearAllVisible(page);
visibilitymap_clear(rel, blkno, vmbuf,
VISIBILITYMAP_VALID_BITS);
did_modify_vm = true;
}
}
else
{
HeapTupleHeader htup;
Assert(heap_force_opt == HEAP_FORCE_FREEZE);
htup = (HeapTupleHeader) PageGetItem(page, itemid);
/*
* Reset all visibility-related fields of the tuple. This
* logic should mimic heap_execute_freeze_tuple(), but we
* choose to reset xmin and ctid just to be sure that no
* potentially-garbled data is left behind.
*/
ItemPointerSet(&htup->t_ctid, blkno, curoff);
HeapTupleHeaderSetXmin(htup, FrozenTransactionId);
HeapTupleHeaderSetXmax(htup, InvalidTransactionId);
if (htup->t_infomask & HEAP_MOVED)
{
if (htup->t_infomask & HEAP_MOVED_OFF)
HeapTupleHeaderSetXvac(htup, InvalidTransactionId);
else
HeapTupleHeaderSetXvac(htup, FrozenTransactionId);
}
/*
* Clear all the visibility-related bits of this tuple and
* mark it as frozen. Also, get rid of HOT_UPDATED and
* KEYS_UPDATES bits.
*/
htup->t_infomask &= ~HEAP_XACT_MASK;
htup->t_infomask |= (HEAP_XMIN_FROZEN | HEAP_XMAX_INVALID);
htup->t_infomask2 &= ~HEAP_HOT_UPDATED;
htup->t_infomask2 &= ~HEAP_KEYS_UPDATED;
}
}
/*
* If the page was modified, only then, we mark the buffer dirty or do
* the WAL logging.
*/
if (did_modify_page)
{
/* Mark buffer dirty before we write WAL. */
MarkBufferDirty(buf);
/* XLOG stuff */
if (RelationNeedsWAL(rel))
log_newpage_buffer(buf, true);
}
/* WAL log the VM page if it was modified. */
if (did_modify_vm && RelationNeedsWAL(rel))
log_newpage_buffer(vmbuf, false);
END_CRIT_SECTION();
UnlockReleaseBuffer(buf);
if (vmbuf != InvalidBuffer)
ReleaseBuffer(vmbuf);
/* Update the current_start_ptr before moving to the next page. */
curr_start_ptr = next_start_ptr;
}
relation_close(rel, RowExclusiveLock);
pfree(ta);
PG_RETURN_VOID();
}
/*-------------------------------------------------------------------------
* tidcmp()
*
* Compare two item pointers, return -1, 0, or +1.
*
* See ItemPointerCompare for details.
* ------------------------------------------------------------------------
*/
static int32
tidcmp(const void *a, const void *b)
{
ItemPointer iptr1 = ((const ItemPointer) a);
ItemPointer iptr2 = ((const ItemPointer) b);
return ItemPointerCompare(iptr1, iptr2);
}
/*-------------------------------------------------------------------------
* sanity_check_tid_array()
*
* Perform sanity checks on the given tid array, and set *ntids to the
* number of items in the array.
* ------------------------------------------------------------------------
*/
static void
sanity_check_tid_array(ArrayType *ta, int *ntids)
{
if (ARR_HASNULL(ta) && array_contains_nulls(ta))
ereport(ERROR,
(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
errmsg("array must not contain nulls")));
if (ARR_NDIM(ta) > 1)
ereport(ERROR,
(errcode(ERRCODE_DATA_EXCEPTION),
errmsg("argument must be empty or one-dimensional array")));
*ntids = ArrayGetNItems(ARR_NDIM(ta), ARR_DIMS(ta));
}
/*-------------------------------------------------------------------------
* find_tids_one_page()
*
* Find all the tids residing in the same page as tids[next_start_ptr], and
* update next_start_ptr so that it points to the first tid in the next page.
*
* NOTE: The input tids[] array must be sorted.
* ------------------------------------------------------------------------
*/
static BlockNumber
find_tids_one_page(ItemPointer tids, int ntids, OffsetNumber *next_start_ptr)
{
int i;
BlockNumber prev_blkno,
blkno;
prev_blkno = blkno = InvalidBlockNumber;
for (i = *next_start_ptr; i < ntids; i++)
{
ItemPointerData tid = tids[i];
blkno = ItemPointerGetBlockNumberNoCheck(&tid);
if (i == *next_start_ptr)
prev_blkno = blkno;
if (prev_blkno != blkno)
break;
}
*next_start_ptr = i;
return prev_blkno;
}
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