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postgres/contrib/amcheck/verify_heapam.c
David Rowley 84fd3bc141 Fix a few duplicate words in comments 
These are all new to v18

Author: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAApHDvrMcr8XD107H3NV=WHgyBcu=sx5+7=WArr-n_cWUqdFXQ@mail.gmail.com
2025-04-21 10:41:18 +12:00

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/*-------------------------------------------------------------------------
*
* verify_heapam.c
* Functions to check postgresql heap relations for corruption
*
* Copyright (c) 2016-2025, PostgreSQL Global Development Group
*
* contrib/amcheck/verify_heapam.c
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/detoast.h"
#include "access/genam.h"
#include "access/heaptoast.h"
#include "access/multixact.h"
#include "access/relation.h"
#include "access/table.h"
#include "access/toast_internals.h"
#include "access/visibilitymap.h"
#include "access/xact.h"
#include "catalog/pg_am.h"
#include "catalog/pg_class.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "storage/procarray.h"
#include "storage/read_stream.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/rel.h"
PG_FUNCTION_INFO_V1(verify_heapam);
/* The number of columns in tuples returned by verify_heapam */
#define HEAPCHECK_RELATION_COLS 4
/* The largest valid toast va_rawsize */
#define VARLENA_SIZE_LIMIT 0x3FFFFFFF
/*
* Despite the name, we use this for reporting problems with both XIDs and
* MXIDs.
*/
typedef enum XidBoundsViolation
{
XID_INVALID,
XID_IN_FUTURE,
XID_PRECEDES_CLUSTERMIN,
XID_PRECEDES_RELMIN,
XID_BOUNDS_OK,
} XidBoundsViolation;
typedef enum XidCommitStatus
{
XID_COMMITTED,
XID_IS_CURRENT_XID,
XID_IN_PROGRESS,
XID_ABORTED,
} XidCommitStatus;
typedef enum SkipPages
{
SKIP_PAGES_ALL_FROZEN,
SKIP_PAGES_ALL_VISIBLE,
SKIP_PAGES_NONE,
} SkipPages;
/*
* Struct holding information about a toasted attribute sufficient to both
* check the toasted attribute and, if found to be corrupt, to report where it
* was encountered in the main table.
*/
typedef struct ToastedAttribute
{
struct varatt_external toast_pointer;
BlockNumber blkno; /* block in main table */
OffsetNumber offnum; /* offset in main table */
AttrNumber attnum; /* attribute in main table */
} ToastedAttribute;
/*
* Struct holding the running context information during
* a lifetime of a verify_heapam execution.
*/
typedef struct HeapCheckContext
{
/*
* Cached copies of values from TransamVariables and computed values from
* them.
*/
FullTransactionId next_fxid; /* TransamVariables->nextXid */
TransactionId next_xid; /* 32-bit version of next_fxid */
TransactionId oldest_xid; /* TransamVariables->oldestXid */
FullTransactionId oldest_fxid; /* 64-bit version of oldest_xid, computed
* relative to next_fxid */
TransactionId safe_xmin; /* this XID and newer ones can't become
* all-visible while we're running */
/*
* Cached copy of value from MultiXactState
*/
MultiXactId next_mxact; /* MultiXactState->nextMXact */
MultiXactId oldest_mxact; /* MultiXactState->oldestMultiXactId */
/*
* Cached copies of the most recently checked xid and its status.
*/
TransactionId cached_xid;
XidCommitStatus cached_status;
/* Values concerning the heap relation being checked */
Relation rel;
TransactionId relfrozenxid;
FullTransactionId relfrozenfxid;
TransactionId relminmxid;
Relation toast_rel;
Relation *toast_indexes;
Relation valid_toast_index;
int num_toast_indexes;
/*
* Values for iterating over pages in the relation. `blkno` is the most
* recent block in the buffer yielded by the read stream API.
*/
BlockNumber blkno;
BufferAccessStrategy bstrategy;
Buffer buffer;
Page page;
/* Values for iterating over tuples within a page */
OffsetNumber offnum;
ItemId itemid;
uint16 lp_len;
uint16 lp_off;
HeapTupleHeader tuphdr;
int natts;
/* Values for iterating over attributes within the tuple */
uint32 offset; /* offset in tuple data */
AttrNumber attnum;
/* True if tuple's xmax makes it eligible for pruning */
bool tuple_could_be_pruned;
/*
* List of ToastedAttribute structs for toasted attributes which are not
* eligible for pruning and should be checked
*/
List *toasted_attributes;
/* Whether verify_heapam has yet encountered any corrupt tuples */
bool is_corrupt;
/* The descriptor and tuplestore for verify_heapam's result tuples */
TupleDesc tupdesc;
Tuplestorestate *tupstore;
} HeapCheckContext;
/*
* The per-relation data provided to the read stream API for heap amcheck to
* use in its callback for the SKIP_PAGES_ALL_FROZEN and
* SKIP_PAGES_ALL_VISIBLE options.
*/
typedef struct HeapCheckReadStreamData
{
/*
* `range` is used by all SkipPages options. SKIP_PAGES_NONE uses the
* default read stream callback, block_range_read_stream_cb(), which takes
* a BlockRangeReadStreamPrivate as its callback_private_data. `range`
* keeps track of the current block number across
* read_stream_next_buffer() invocations.
*/
BlockRangeReadStreamPrivate range;
SkipPages skip_option;
Relation rel;
Buffer *vmbuffer;
} HeapCheckReadStreamData;
/* Internal implementation */
static BlockNumber heapcheck_read_stream_next_unskippable(ReadStream *stream,
void *callback_private_data,
void *per_buffer_data);
static void check_tuple(HeapCheckContext *ctx,
bool *xmin_commit_status_ok,
XidCommitStatus *xmin_commit_status);
static void check_toast_tuple(HeapTuple toasttup, HeapCheckContext *ctx,
ToastedAttribute *ta, int32 *expected_chunk_seq,
uint32 extsize);
static bool check_tuple_attribute(HeapCheckContext *ctx);
static void check_toasted_attribute(HeapCheckContext *ctx,
ToastedAttribute *ta);
static bool check_tuple_header(HeapCheckContext *ctx);
static bool check_tuple_visibility(HeapCheckContext *ctx,
bool *xmin_commit_status_ok,
XidCommitStatus *xmin_commit_status);
static void report_corruption(HeapCheckContext *ctx, char *msg);
static void report_toast_corruption(HeapCheckContext *ctx,
ToastedAttribute *ta, char *msg);
static FullTransactionId FullTransactionIdFromXidAndCtx(TransactionId xid,
const HeapCheckContext *ctx);
static void update_cached_xid_range(HeapCheckContext *ctx);
static void update_cached_mxid_range(HeapCheckContext *ctx);
static XidBoundsViolation check_mxid_in_range(MultiXactId mxid,
HeapCheckContext *ctx);
static XidBoundsViolation check_mxid_valid_in_rel(MultiXactId mxid,
HeapCheckContext *ctx);
static XidBoundsViolation get_xid_status(TransactionId xid,
HeapCheckContext *ctx,
XidCommitStatus *status);
/*
* Scan and report corruption in heap pages, optionally reconciling toasted
* attributes with entries in the associated toast table. Intended to be
* called from SQL with the following parameters:
*
* relation:
* The Oid of the heap relation to be checked.
*
* on_error_stop:
* Whether to stop at the end of the first page for which errors are
* detected. Note that multiple rows may be returned.
*
* check_toast:
* Whether to check each toasted attribute against the toast table to
* verify that it can be found there.
*
* skip:
* What kinds of pages in the heap relation should be skipped. Valid
* options are "all-visible", "all-frozen", and "none".
*
* Returns to the SQL caller a set of tuples, each containing the location
* and a description of a corruption found in the heap.
*
* This code goes to some trouble to avoid crashing the server even if the
* table pages are badly corrupted, but it's probably not perfect. If
* check_toast is true, we'll use regular index lookups to try to fetch TOAST
* tuples, which can certainly cause crashes if the right kind of corruption
* exists in the toast table or index. No matter what parameters you pass,
* we can't protect against crashes that might occur trying to look up the
* commit status of transaction IDs (though we avoid trying to do such lookups
* for transaction IDs that can't legally appear in the table).
*/
Datum
verify_heapam(PG_FUNCTION_ARGS)
{
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
HeapCheckContext ctx;
Buffer vmbuffer = InvalidBuffer;
Oid relid;
bool on_error_stop;
bool check_toast;
SkipPages skip_option = SKIP_PAGES_NONE;
BlockNumber first_block;
BlockNumber last_block;
BlockNumber nblocks;
const char *skip;
ReadStream *stream;
int stream_flags;
ReadStreamBlockNumberCB stream_cb;
void *stream_data;
HeapCheckReadStreamData stream_skip_data;
/* Check supplied arguments */
if (PG_ARGISNULL(0))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("relation cannot be null")));
relid = PG_GETARG_OID(0);
if (PG_ARGISNULL(1))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("on_error_stop cannot be null")));
on_error_stop = PG_GETARG_BOOL(1);
if (PG_ARGISNULL(2))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("check_toast cannot be null")));
check_toast = PG_GETARG_BOOL(2);
if (PG_ARGISNULL(3))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("skip cannot be null")));
skip = text_to_cstring(PG_GETARG_TEXT_PP(3));
if (pg_strcasecmp(skip, "all-visible") == 0)
skip_option = SKIP_PAGES_ALL_VISIBLE;
else if (pg_strcasecmp(skip, "all-frozen") == 0)
skip_option = SKIP_PAGES_ALL_FROZEN;
else if (pg_strcasecmp(skip, "none") == 0)
skip_option = SKIP_PAGES_NONE;
else
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("invalid skip option"),
errhint("Valid skip options are \"all-visible\", \"all-frozen\", and \"none\".")));
memset(&ctx, 0, sizeof(HeapCheckContext));
ctx.cached_xid = InvalidTransactionId;
ctx.toasted_attributes = NIL;
/*
* Any xmin newer than the xmin of our snapshot can't become all-visible
* while we're running.
*/
ctx.safe_xmin = GetTransactionSnapshot()->xmin;
/*
* If we report corruption when not examining some individual attribute,
* we need attnum to be reported as NULL. Set that up before any
* corruption reporting might happen.
*/
ctx.attnum = -1;
/* Construct the tuplestore and tuple descriptor */
InitMaterializedSRF(fcinfo, 0);
ctx.tupdesc = rsinfo->setDesc;
ctx.tupstore = rsinfo->setResult;
/* Open relation, check relkind and access method */
ctx.rel = relation_open(relid, AccessShareLock);
/*
* Check that a relation's relkind and access method are both supported.
*/
if (!RELKIND_HAS_TABLE_AM(ctx.rel->rd_rel->relkind) &&
ctx.rel->rd_rel->relkind != RELKIND_SEQUENCE)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("cannot check relation \"%s\"",
RelationGetRelationName(ctx.rel)),
errdetail_relkind_not_supported(ctx.rel->rd_rel->relkind)));
/*
* Sequences always use heap AM, but they don't show that in the catalogs.
* Other relkinds might be using a different AM, so check.
*/
if (ctx.rel->rd_rel->relkind != RELKIND_SEQUENCE &&
ctx.rel->rd_rel->relam != HEAP_TABLE_AM_OID)
ereport(ERROR,
(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
errmsg("only heap AM is supported")));
/*
* Early exit for unlogged relations during recovery. These will have no
* relation fork, so there won't be anything to check. We behave as if
* the relation is empty.
*/
if (ctx.rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED &&
RecoveryInProgress())
{
ereport(DEBUG1,
(errcode(ERRCODE_READ_ONLY_SQL_TRANSACTION),
errmsg("cannot verify unlogged relation \"%s\" during recovery, skipping",
RelationGetRelationName(ctx.rel))));
relation_close(ctx.rel, AccessShareLock);
PG_RETURN_NULL();
}
/* Early exit if the relation is empty */
nblocks = RelationGetNumberOfBlocks(ctx.rel);
if (!nblocks)
{
relation_close(ctx.rel, AccessShareLock);
PG_RETURN_NULL();
}
ctx.bstrategy = GetAccessStrategy(BAS_BULKREAD);
ctx.buffer = InvalidBuffer;
ctx.page = NULL;
/* Validate block numbers, or handle nulls. */
if (PG_ARGISNULL(4))
first_block = 0;
else
{
int64 fb = PG_GETARG_INT64(4);
if (fb < 0 || fb >= nblocks)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("starting block number must be between 0 and %u",
nblocks - 1)));
first_block = (BlockNumber) fb;
}
if (PG_ARGISNULL(5))
last_block = nblocks - 1;
else
{
int64 lb = PG_GETARG_INT64(5);
if (lb < 0 || lb >= nblocks)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("ending block number must be between 0 and %u",
nblocks - 1)));
last_block = (BlockNumber) lb;
}
/* Optionally open the toast relation, if any. */
if (ctx.rel->rd_rel->reltoastrelid && check_toast)
{
int offset;
/* Main relation has associated toast relation */
ctx.toast_rel = table_open(ctx.rel->rd_rel->reltoastrelid,
AccessShareLock);
offset = toast_open_indexes(ctx.toast_rel,
AccessShareLock,
&(ctx.toast_indexes),
&(ctx.num_toast_indexes));
ctx.valid_toast_index = ctx.toast_indexes[offset];
}
else
{
/*
* Main relation has no associated toast relation, or we're
* intentionally skipping it.
*/
ctx.toast_rel = NULL;
ctx.toast_indexes = NULL;
ctx.num_toast_indexes = 0;
}
update_cached_xid_range(&ctx);
update_cached_mxid_range(&ctx);
ctx.relfrozenxid = ctx.rel->rd_rel->relfrozenxid;
ctx.relfrozenfxid = FullTransactionIdFromXidAndCtx(ctx.relfrozenxid, &ctx);
ctx.relminmxid = ctx.rel->rd_rel->relminmxid;
if (TransactionIdIsNormal(ctx.relfrozenxid))
ctx.oldest_xid = ctx.relfrozenxid;
/* Now that `ctx` is set up, set up the read stream */
stream_skip_data.range.current_blocknum = first_block;
stream_skip_data.range.last_exclusive = last_block + 1;
stream_skip_data.skip_option = skip_option;
stream_skip_data.rel = ctx.rel;
stream_skip_data.vmbuffer = &vmbuffer;
if (skip_option == SKIP_PAGES_NONE)
{
/*
* It is safe to use batchmode as block_range_read_stream_cb takes no
* locks.
*/
stream_cb = block_range_read_stream_cb;
stream_flags = READ_STREAM_SEQUENTIAL |
READ_STREAM_FULL |
READ_STREAM_USE_BATCHING;
stream_data = &stream_skip_data.range;
}
else
{
/*
* It would not be safe to naively use batchmode, as
* heapcheck_read_stream_next_unskippable takes locks. It shouldn't be
* too hard to convert though.
*/
stream_cb = heapcheck_read_stream_next_unskippable;
stream_flags = READ_STREAM_DEFAULT;
stream_data = &stream_skip_data;
}
stream = read_stream_begin_relation(stream_flags,
ctx.bstrategy,
ctx.rel,
MAIN_FORKNUM,
stream_cb,
stream_data,
0);
while ((ctx.buffer = read_stream_next_buffer(stream, NULL)) != InvalidBuffer)
{
OffsetNumber maxoff;
OffsetNumber predecessor[MaxOffsetNumber];
OffsetNumber successor[MaxOffsetNumber];
bool lp_valid[MaxOffsetNumber];
bool xmin_commit_status_ok[MaxOffsetNumber];
XidCommitStatus xmin_commit_status[MaxOffsetNumber];
CHECK_FOR_INTERRUPTS();
memset(predecessor, 0, sizeof(OffsetNumber) * MaxOffsetNumber);
/* Lock the next page. */
Assert(BufferIsValid(ctx.buffer));
LockBuffer(ctx.buffer, BUFFER_LOCK_SHARE);
ctx.blkno = BufferGetBlockNumber(ctx.buffer);
ctx.page = BufferGetPage(ctx.buffer);
/* Perform tuple checks */
maxoff = PageGetMaxOffsetNumber(ctx.page);
for (ctx.offnum = FirstOffsetNumber; ctx.offnum <= maxoff;
ctx.offnum = OffsetNumberNext(ctx.offnum))
{
BlockNumber nextblkno;
OffsetNumber nextoffnum;
successor[ctx.offnum] = InvalidOffsetNumber;
lp_valid[ctx.offnum] = false;
xmin_commit_status_ok[ctx.offnum] = false;
ctx.itemid = PageGetItemId(ctx.page, ctx.offnum);
/* Skip over unused/dead line pointers */
if (!ItemIdIsUsed(ctx.itemid) || ItemIdIsDead(ctx.itemid))
continue;
/*
* If this line pointer has been redirected, check that it
* redirects to a valid offset within the line pointer array
*/
if (ItemIdIsRedirected(ctx.itemid))
{
OffsetNumber rdoffnum = ItemIdGetRedirect(ctx.itemid);
ItemId rditem;
if (rdoffnum < FirstOffsetNumber)
{
report_corruption(&ctx,
psprintf("line pointer redirection to item at offset %u precedes minimum offset %u",
(unsigned) rdoffnum,
(unsigned) FirstOffsetNumber));
continue;
}
if (rdoffnum > maxoff)
{
report_corruption(&ctx,
psprintf("line pointer redirection to item at offset %u exceeds maximum offset %u",
(unsigned) rdoffnum,
(unsigned) maxoff));
continue;
}
/*
* Since we've checked that this redirect points to a line
* pointer between FirstOffsetNumber and maxoff, it should now
* be safe to fetch the referenced line pointer. We expect it
* to be LP_NORMAL; if not, that's corruption.
*/
rditem = PageGetItemId(ctx.page, rdoffnum);
if (!ItemIdIsUsed(rditem))
{
report_corruption(&ctx,
psprintf("redirected line pointer points to an unused item at offset %u",
(unsigned) rdoffnum));
continue;
}
else if (ItemIdIsDead(rditem))
{
report_corruption(&ctx,
psprintf("redirected line pointer points to a dead item at offset %u",
(unsigned) rdoffnum));
continue;
}
else if (ItemIdIsRedirected(rditem))
{
report_corruption(&ctx,
psprintf("redirected line pointer points to another redirected line pointer at offset %u",
(unsigned) rdoffnum));
continue;
}
/*
* Record the fact that this line pointer has passed basic
* sanity checking, and also the offset number to which it
* points.
*/
lp_valid[ctx.offnum] = true;
successor[ctx.offnum] = rdoffnum;
continue;
}
/* Sanity-check the line pointer's offset and length values */
ctx.lp_len = ItemIdGetLength(ctx.itemid);
ctx.lp_off = ItemIdGetOffset(ctx.itemid);
if (ctx.lp_off != MAXALIGN(ctx.lp_off))
{
report_corruption(&ctx,
psprintf("line pointer to page offset %u is not maximally aligned",
ctx.lp_off));
continue;
}
if (ctx.lp_len < MAXALIGN(SizeofHeapTupleHeader))
{
report_corruption(&ctx,
psprintf("line pointer length %u is less than the minimum tuple header size %u",
ctx.lp_len,
(unsigned) MAXALIGN(SizeofHeapTupleHeader)));
continue;
}
if (ctx.lp_off + ctx.lp_len > BLCKSZ)
{
report_corruption(&ctx,
psprintf("line pointer to page offset %u with length %u ends beyond maximum page offset %u",
ctx.lp_off,
ctx.lp_len,
(unsigned) BLCKSZ));
continue;
}
/* It should be safe to examine the tuple's header, at least */
lp_valid[ctx.offnum] = true;
ctx.tuphdr = (HeapTupleHeader) PageGetItem(ctx.page, ctx.itemid);
ctx.natts = HeapTupleHeaderGetNatts(ctx.tuphdr);
/* Ok, ready to check this next tuple */
check_tuple(&ctx,
&xmin_commit_status_ok[ctx.offnum],
&xmin_commit_status[ctx.offnum]);
/*
* If the CTID field of this tuple seems to point to another tuple
* on the same page, record that tuple as the successor of this
* one.
*/
nextblkno = ItemPointerGetBlockNumber(&(ctx.tuphdr)->t_ctid);
nextoffnum = ItemPointerGetOffsetNumber(&(ctx.tuphdr)->t_ctid);
if (nextblkno == ctx.blkno && nextoffnum != ctx.offnum &&
nextoffnum >= FirstOffsetNumber && nextoffnum <= maxoff)
successor[ctx.offnum] = nextoffnum;
}
/*
* Update chain validation. Check each line pointer that's got a valid
* successor against that successor.
*/
ctx.attnum = -1;
for (ctx.offnum = FirstOffsetNumber; ctx.offnum <= maxoff;
ctx.offnum = OffsetNumberNext(ctx.offnum))
{
ItemId curr_lp;
ItemId next_lp;
HeapTupleHeader curr_htup;
HeapTupleHeader next_htup;
TransactionId curr_xmin;
TransactionId curr_xmax;
TransactionId next_xmin;
OffsetNumber nextoffnum = successor[ctx.offnum];
/*
* The current line pointer may not have a successor, either
* because it's not valid or because it didn't point to anything.
* In either case, we have to give up.
*
* If the current line pointer does point to something, it's
* possible that the target line pointer isn't valid. We have to
* give up in that case, too.
*/
if (nextoffnum == InvalidOffsetNumber || !lp_valid[nextoffnum])
continue;
/* We have two valid line pointers that we can examine. */
curr_lp = PageGetItemId(ctx.page, ctx.offnum);
next_lp = PageGetItemId(ctx.page, nextoffnum);
/* Handle the cases where the current line pointer is a redirect. */
if (ItemIdIsRedirected(curr_lp))
{
/*
* We should not have set successor[ctx.offnum] to a value
* other than InvalidOffsetNumber unless that line pointer is
* LP_NORMAL.
*/
Assert(ItemIdIsNormal(next_lp));
/* Can only redirect to a HOT tuple. */
next_htup = (HeapTupleHeader) PageGetItem(ctx.page, next_lp);
if (!HeapTupleHeaderIsHeapOnly(next_htup))
{
report_corruption(&ctx,
psprintf("redirected line pointer points to a non-heap-only tuple at offset %u",
(unsigned) nextoffnum));
}
/* HOT chains should not intersect. */
if (predecessor[nextoffnum] != InvalidOffsetNumber)
{
report_corruption(&ctx,
psprintf("redirect line pointer points to offset %u, but offset %u also points there",
(unsigned) nextoffnum, (unsigned) predecessor[nextoffnum]));
continue;
}
/*
* This redirect and the tuple to which it points seem to be
* part of an update chain.
*/
predecessor[nextoffnum] = ctx.offnum;
continue;
}
/*
* If the next line pointer is a redirect, or if it's a tuple but
* the XMAX of this tuple doesn't match the XMIN of the next
* tuple, then the two aren't part of the same update chain and
* there is nothing more to do.
*/
if (ItemIdIsRedirected(next_lp))
continue;
curr_htup = (HeapTupleHeader) PageGetItem(ctx.page, curr_lp);
curr_xmax = HeapTupleHeaderGetUpdateXid(curr_htup);
next_htup = (HeapTupleHeader) PageGetItem(ctx.page, next_lp);
next_xmin = HeapTupleHeaderGetXmin(next_htup);
if (!TransactionIdIsValid(curr_xmax) ||
!TransactionIdEquals(curr_xmax, next_xmin))
continue;
/* HOT chains should not intersect. */
if (predecessor[nextoffnum] != InvalidOffsetNumber)
{
report_corruption(&ctx,
psprintf("tuple points to new version at offset %u, but offset %u also points there",
(unsigned) nextoffnum, (unsigned) predecessor[nextoffnum]));
continue;
}
/*
* This tuple and the tuple to which it points seem to be part of
* an update chain.
*/
predecessor[nextoffnum] = ctx.offnum;
/*
* If the current tuple is marked as HOT-updated, then the next
* tuple should be marked as a heap-only tuple. Conversely, if the
* current tuple isn't marked as HOT-updated, then the next tuple
* shouldn't be marked as a heap-only tuple.
*
* NB: Can't use HeapTupleHeaderIsHotUpdated() as it checks if
* hint bits indicate xmin/xmax aborted.
*/
if (!(curr_htup->t_infomask2 & HEAP_HOT_UPDATED) &&
HeapTupleHeaderIsHeapOnly(next_htup))
{
report_corruption(&ctx,
psprintf("non-heap-only update produced a heap-only tuple at offset %u",
(unsigned) nextoffnum));
}
if ((curr_htup->t_infomask2 & HEAP_HOT_UPDATED) &&
!HeapTupleHeaderIsHeapOnly(next_htup))
{
report_corruption(&ctx,
psprintf("heap-only update produced a non-heap only tuple at offset %u",
(unsigned) nextoffnum));
}
/*
* If the current tuple's xmin is still in progress but the
* successor tuple's xmin is committed, that's corruption.
*
* NB: We recheck the commit status of the current tuple's xmin
* here, because it might have committed after we checked it and
* before we checked the commit status of the successor tuple's
* xmin. This should be safe because the xmin itself can't have
* changed, only its commit status.
*/
curr_xmin = HeapTupleHeaderGetXmin(curr_htup);
if (xmin_commit_status_ok[ctx.offnum] &&
xmin_commit_status[ctx.offnum] == XID_IN_PROGRESS &&
xmin_commit_status_ok[nextoffnum] &&
xmin_commit_status[nextoffnum] == XID_COMMITTED &&
TransactionIdIsInProgress(curr_xmin))
{
report_corruption(&ctx,
psprintf("tuple with in-progress xmin %u was updated to produce a tuple at offset %u with committed xmin %u",
(unsigned) curr_xmin,
(unsigned) ctx.offnum,
(unsigned) next_xmin));
}
/*
* If the current tuple's xmin is aborted but the successor
* tuple's xmin is in-progress or committed, that's corruption.
*/
if (xmin_commit_status_ok[ctx.offnum] &&
xmin_commit_status[ctx.offnum] == XID_ABORTED &&
xmin_commit_status_ok[nextoffnum])
{
if (xmin_commit_status[nextoffnum] == XID_IN_PROGRESS)
report_corruption(&ctx,
psprintf("tuple with aborted xmin %u was updated to produce a tuple at offset %u with in-progress xmin %u",
(unsigned) curr_xmin,
(unsigned) ctx.offnum,
(unsigned) next_xmin));
else if (xmin_commit_status[nextoffnum] == XID_COMMITTED)
report_corruption(&ctx,
psprintf("tuple with aborted xmin %u was updated to produce a tuple at offset %u with committed xmin %u",
(unsigned) curr_xmin,
(unsigned) ctx.offnum,
(unsigned) next_xmin));
}
}
/*
* An update chain can start either with a non-heap-only tuple or with
* a redirect line pointer, but not with a heap-only tuple.
*
* (This check is in a separate loop because we need the predecessor
* array to be fully populated before we can perform it.)
*/
for (ctx.offnum = FirstOffsetNumber;
ctx.offnum <= maxoff;
ctx.offnum = OffsetNumberNext(ctx.offnum))
{
if (xmin_commit_status_ok[ctx.offnum] &&
(xmin_commit_status[ctx.offnum] == XID_COMMITTED ||
xmin_commit_status[ctx.offnum] == XID_IN_PROGRESS) &&
predecessor[ctx.offnum] == InvalidOffsetNumber)
{
ItemId curr_lp;
curr_lp = PageGetItemId(ctx.page, ctx.offnum);
if (!ItemIdIsRedirected(curr_lp))
{
HeapTupleHeader curr_htup;
curr_htup = (HeapTupleHeader)
PageGetItem(ctx.page, curr_lp);
if (HeapTupleHeaderIsHeapOnly(curr_htup))
report_corruption(&ctx,
psprintf("tuple is root of chain but is marked as heap-only tuple"));
}
}
}
/* clean up */
UnlockReleaseBuffer(ctx.buffer);
/*
* Check any toast pointers from the page whose lock we just released
*/
if (ctx.toasted_attributes != NIL)
{
ListCell *cell;
foreach(cell, ctx.toasted_attributes)
check_toasted_attribute(&ctx, lfirst(cell));
list_free_deep(ctx.toasted_attributes);
ctx.toasted_attributes = NIL;
}
if (on_error_stop && ctx.is_corrupt)
break;
}
read_stream_end(stream);
if (vmbuffer != InvalidBuffer)
ReleaseBuffer(vmbuffer);
/* Close the associated toast table and indexes, if any. */
if (ctx.toast_indexes)
toast_close_indexes(ctx.toast_indexes, ctx.num_toast_indexes,
AccessShareLock);
if (ctx.toast_rel)
table_close(ctx.toast_rel, AccessShareLock);
/* Close the main relation */
relation_close(ctx.rel, AccessShareLock);
PG_RETURN_NULL();
}
/*
* Heap amcheck's read stream callback for getting the next unskippable block.
* This callback is only used when 'all-visible' or 'all-frozen' is provided
* as the skip option to verify_heapam(). With the default 'none',
* block_range_read_stream_cb() is used instead.
*/
static BlockNumber
heapcheck_read_stream_next_unskippable(ReadStream *stream,
void *callback_private_data,
void *per_buffer_data)
{
HeapCheckReadStreamData *p = callback_private_data;
/* Loops over [current_blocknum, last_exclusive) blocks */
for (BlockNumber i; (i = p->range.current_blocknum++) < p->range.last_exclusive;)
{
uint8 mapbits = visibilitymap_get_status(p->rel, i, p->vmbuffer);
if (p->skip_option == SKIP_PAGES_ALL_FROZEN)
{
if ((mapbits & VISIBILITYMAP_ALL_FROZEN) != 0)
continue;
}
if (p->skip_option == SKIP_PAGES_ALL_VISIBLE)
{
if ((mapbits & VISIBILITYMAP_ALL_VISIBLE) != 0)
continue;
}
return i;
}
return InvalidBlockNumber;
}
/*
* Shared internal implementation for report_corruption and
* report_toast_corruption.
*/
static void
report_corruption_internal(Tuplestorestate *tupstore, TupleDesc tupdesc,
BlockNumber blkno, OffsetNumber offnum,
AttrNumber attnum, char *msg)
{
Datum values[HEAPCHECK_RELATION_COLS] = {0};
bool nulls[HEAPCHECK_RELATION_COLS] = {0};
HeapTuple tuple;
values[0] = Int64GetDatum(blkno);
values[1] = Int32GetDatum(offnum);
values[2] = Int32GetDatum(attnum);
nulls[2] = (attnum < 0);
values[3] = CStringGetTextDatum(msg);
/*
* In principle, there is nothing to prevent a scan over a large, highly
* corrupted table from using work_mem worth of memory building up the
* tuplestore. That's ok, but if we also leak the msg argument memory
* until the end of the query, we could exceed work_mem by more than a
* trivial amount. Therefore, free the msg argument each time we are
* called rather than waiting for our current memory context to be freed.
*/
pfree(msg);
tuple = heap_form_tuple(tupdesc, values, nulls);
tuplestore_puttuple(tupstore, tuple);
}
/*
* Record a single corruption found in the main table. The values in ctx should
* indicate the location of the corruption, and the msg argument should contain
* a human-readable description of the corruption.
*
* The msg argument is pfree'd by this function.
*/
static void
report_corruption(HeapCheckContext *ctx, char *msg)
{
report_corruption_internal(ctx->tupstore, ctx->tupdesc, ctx->blkno,
ctx->offnum, ctx->attnum, msg);
ctx->is_corrupt = true;
}
/*
* Record corruption found in the toast table. The values in ta should
* indicate the location in the main table where the toast pointer was
* encountered, and the msg argument should contain a human-readable
* description of the toast table corruption.
*
* As above, the msg argument is pfree'd by this function.
*/
static void
report_toast_corruption(HeapCheckContext *ctx, ToastedAttribute *ta,
char *msg)
{
report_corruption_internal(ctx->tupstore, ctx->tupdesc, ta->blkno,
ta->offnum, ta->attnum, msg);
ctx->is_corrupt = true;
}
/*
* Check for tuple header corruption.
*
* Some kinds of corruption make it unsafe to check the tuple attributes, for
* example when the line pointer refers to a range of bytes outside the page.
* In such cases, we return false (not checkable) after recording appropriate
* corruption messages.
*
* Some other kinds of tuple header corruption confuse the question of where
* the tuple attributes begin, or how long the nulls bitmap is, etc., making it
* unreasonable to attempt to check attributes, even if all candidate answers
* to those questions would not result in reading past the end of the line
* pointer or page. In such cases, like above, we record corruption messages
* about the header and then return false.
*
* Other kinds of tuple header corruption do not bear on the question of
* whether the tuple attributes can be checked, so we record corruption
* messages for them but we do not return false merely because we detected
* them.
*
* Returns whether the tuple is sufficiently sensible to undergo visibility and
* attribute checks.
*/
static bool
check_tuple_header(HeapCheckContext *ctx)
{
HeapTupleHeader tuphdr = ctx->tuphdr;
uint16 infomask = tuphdr->t_infomask;
TransactionId curr_xmax = HeapTupleHeaderGetUpdateXid(tuphdr);
bool result = true;
unsigned expected_hoff;
if (ctx->tuphdr->t_hoff > ctx->lp_len)
{
report_corruption(ctx,
psprintf("data begins at offset %u beyond the tuple length %u",
ctx->tuphdr->t_hoff, ctx->lp_len));
result = false;
}
if ((ctx->tuphdr->t_infomask & HEAP_XMAX_COMMITTED) &&
(ctx->tuphdr->t_infomask & HEAP_XMAX_IS_MULTI))
{
report_corruption(ctx,
pstrdup("multixact should not be marked committed"));
/*
* This condition is clearly wrong, but it's not enough to justify
* skipping further checks, because we don't rely on this to determine
* whether the tuple is visible or to interpret other relevant header
* fields.
*/
}
if (!TransactionIdIsValid(curr_xmax) &&
HeapTupleHeaderIsHotUpdated(tuphdr))
{
report_corruption(ctx,
psprintf("tuple has been HOT updated, but xmax is 0"));
/*
* As above, even though this shouldn't happen, it's not sufficient
* justification for skipping further checks, we should still be able
* to perform sensibly.
*/
}
if (HeapTupleHeaderIsHeapOnly(tuphdr) &&
((tuphdr->t_infomask & HEAP_UPDATED) == 0))
{
report_corruption(ctx,
psprintf("tuple is heap only, but not the result of an update"));
/* Here again, we can still perform further checks. */
}
if (infomask & HEAP_HASNULL)
expected_hoff = MAXALIGN(SizeofHeapTupleHeader + BITMAPLEN(ctx->natts));
else
expected_hoff = MAXALIGN(SizeofHeapTupleHeader);
if (ctx->tuphdr->t_hoff != expected_hoff)
{
if ((infomask & HEAP_HASNULL) && ctx->natts == 1)
report_corruption(ctx,
psprintf("tuple data should begin at byte %u, but actually begins at byte %u (1 attribute, has nulls)",
expected_hoff, ctx->tuphdr->t_hoff));
else if ((infomask & HEAP_HASNULL))
report_corruption(ctx,
psprintf("tuple data should begin at byte %u, but actually begins at byte %u (%u attributes, has nulls)",
expected_hoff, ctx->tuphdr->t_hoff, ctx->natts));
else if (ctx->natts == 1)
report_corruption(ctx,
psprintf("tuple data should begin at byte %u, but actually begins at byte %u (1 attribute, no nulls)",
expected_hoff, ctx->tuphdr->t_hoff));
else
report_corruption(ctx,
psprintf("tuple data should begin at byte %u, but actually begins at byte %u (%u attributes, no nulls)",
expected_hoff, ctx->tuphdr->t_hoff, ctx->natts));
result = false;
}
return result;
}
/*
* Checks tuple visibility so we know which further checks are safe to
* perform.
*
* If a tuple could have been inserted by a transaction that also added a
* column to the table, but which ultimately did not commit, or which has not
* yet committed, then the table's current TupleDesc might differ from the one
* used to construct this tuple, so we must not check it.
*
* As a special case, if our own transaction inserted the tuple, even if we
* added a column to the table, our TupleDesc should match. We could check the
* tuple, but choose not to do so.
*
* If a tuple has been updated or deleted, we can still read the old tuple for
* corruption checking purposes, as long as we are careful about concurrent
* vacuums. The main table tuple itself cannot be vacuumed away because we
* hold a buffer lock on the page, but if the deleting transaction is older
* than our transaction snapshot's xmin, then vacuum could remove the toast at
* any time, so we must not try to follow TOAST pointers.
*
* If xmin or xmax values are older than can be checked against clog, or appear
* to be in the future (possibly due to wrap-around), then we cannot make a
* determination about the visibility of the tuple, so we skip further checks.
*
* Returns true if the tuple itself should be checked, false otherwise. Sets
* ctx->tuple_could_be_pruned if the tuple -- and thus also any associated
* TOAST tuples -- are eligible for pruning.
*
* Sets *xmin_commit_status_ok to true if the commit status of xmin is known
* and false otherwise. If it's set to true, then also set *xmin_commit_status
* to the actual commit status.
*/
static bool
check_tuple_visibility(HeapCheckContext *ctx, bool *xmin_commit_status_ok,
XidCommitStatus *xmin_commit_status)
{
TransactionId xmin;
TransactionId xvac;
TransactionId xmax;
XidCommitStatus xmin_status;
XidCommitStatus xvac_status;
XidCommitStatus xmax_status;
HeapTupleHeader tuphdr = ctx->tuphdr;
ctx->tuple_could_be_pruned = true; /* have not yet proven otherwise */
*xmin_commit_status_ok = false; /* have not yet proven otherwise */
/* If xmin is normal, it should be within valid range */
xmin = HeapTupleHeaderGetXmin(tuphdr);
switch (get_xid_status(xmin, ctx, &xmin_status))
{
case XID_INVALID:
/* Could be the result of a speculative insertion that aborted. */
return false;
case XID_BOUNDS_OK:
*xmin_commit_status_ok = true;
*xmin_commit_status = xmin_status;
break;
case XID_IN_FUTURE:
report_corruption(ctx,
psprintf("xmin %u equals or exceeds next valid transaction ID %u:%u",
xmin,
EpochFromFullTransactionId(ctx->next_fxid),
XidFromFullTransactionId(ctx->next_fxid)));
return false;
case XID_PRECEDES_CLUSTERMIN:
report_corruption(ctx,
psprintf("xmin %u precedes oldest valid transaction ID %u:%u",
xmin,
EpochFromFullTransactionId(ctx->oldest_fxid),
XidFromFullTransactionId(ctx->oldest_fxid)));
return false;
case XID_PRECEDES_RELMIN:
report_corruption(ctx,
psprintf("xmin %u precedes relation freeze threshold %u:%u",
xmin,
EpochFromFullTransactionId(ctx->relfrozenfxid),
XidFromFullTransactionId(ctx->relfrozenfxid)));
return false;
}
/*
* Has inserting transaction committed?
*/
if (!HeapTupleHeaderXminCommitted(tuphdr))
{
if (HeapTupleHeaderXminInvalid(tuphdr))
return false; /* inserter aborted, don't check */
/* Used by pre-9.0 binary upgrades */
else if (tuphdr->t_infomask & HEAP_MOVED_OFF)
{
xvac = HeapTupleHeaderGetXvac(tuphdr);
switch (get_xid_status(xvac, ctx, &xvac_status))
{
case XID_INVALID:
report_corruption(ctx,
pstrdup("old-style VACUUM FULL transaction ID for moved off tuple is invalid"));
return false;
case XID_IN_FUTURE:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved off tuple equals or exceeds next valid transaction ID %u:%u",
xvac,
EpochFromFullTransactionId(ctx->next_fxid),
XidFromFullTransactionId(ctx->next_fxid)));
return false;
case XID_PRECEDES_RELMIN:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved off tuple precedes relation freeze threshold %u:%u",
xvac,
EpochFromFullTransactionId(ctx->relfrozenfxid),
XidFromFullTransactionId(ctx->relfrozenfxid)));
return false;
case XID_PRECEDES_CLUSTERMIN:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved off tuple precedes oldest valid transaction ID %u:%u",
xvac,
EpochFromFullTransactionId(ctx->oldest_fxid),
XidFromFullTransactionId(ctx->oldest_fxid)));
return false;
case XID_BOUNDS_OK:
break;
}
switch (xvac_status)
{
case XID_IS_CURRENT_XID:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved off tuple matches our current transaction ID",
xvac));
return false;
case XID_IN_PROGRESS:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved off tuple appears to be in progress",
xvac));
return false;
case XID_COMMITTED:
/*
* The tuple is dead, because the xvac transaction moved
* it off and committed. It's checkable, but also
* prunable.
*/
return true;
case XID_ABORTED:
/*
* The original xmin must have committed, because the xvac
* transaction tried to move it later. Since xvac is
* aborted, whether it's still alive now depends on the
* status of xmax.
*/
break;
}
}
/* Used by pre-9.0 binary upgrades */
else if (tuphdr->t_infomask & HEAP_MOVED_IN)
{
xvac = HeapTupleHeaderGetXvac(tuphdr);
switch (get_xid_status(xvac, ctx, &xvac_status))
{
case XID_INVALID:
report_corruption(ctx,
pstrdup("old-style VACUUM FULL transaction ID for moved in tuple is invalid"));
return false;
case XID_IN_FUTURE:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved in tuple equals or exceeds next valid transaction ID %u:%u",
xvac,
EpochFromFullTransactionId(ctx->next_fxid),
XidFromFullTransactionId(ctx->next_fxid)));
return false;
case XID_PRECEDES_RELMIN:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved in tuple precedes relation freeze threshold %u:%u",
xvac,
EpochFromFullTransactionId(ctx->relfrozenfxid),
XidFromFullTransactionId(ctx->relfrozenfxid)));
return false;
case XID_PRECEDES_CLUSTERMIN:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved in tuple precedes oldest valid transaction ID %u:%u",
xvac,
EpochFromFullTransactionId(ctx->oldest_fxid),
XidFromFullTransactionId(ctx->oldest_fxid)));
return false;
case XID_BOUNDS_OK:
break;
}
switch (xvac_status)
{
case XID_IS_CURRENT_XID:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved in tuple matches our current transaction ID",
xvac));
return false;
case XID_IN_PROGRESS:
report_corruption(ctx,
psprintf("old-style VACUUM FULL transaction ID %u for moved in tuple appears to be in progress",
xvac));
return false;
case XID_COMMITTED:
/*
* The original xmin must have committed, because the xvac
* transaction moved it later. Whether it's still alive
* now depends on the status of xmax.
*/
break;
case XID_ABORTED:
/*
* The tuple is dead, because the xvac transaction moved
* it off and committed. It's checkable, but also
* prunable.
*/
return true;
}
}
else if (xmin_status != XID_COMMITTED)
{
/*
* Inserting transaction is not in progress, and not committed, so
* it might have changed the TupleDesc in ways we don't know
* about. Thus, don't try to check the tuple structure.
*
* If xmin_status happens to be XID_IS_CURRENT_XID, then in theory
* any such DDL changes ought to be visible to us, so perhaps we
* could check anyway in that case. But, for now, let's be
* conservative and treat this like any other uncommitted insert.
*/
return false;
}
}
/*
* Okay, the inserter committed, so it was good at some point. Now what
* about the deleting transaction?
*/
if (tuphdr->t_infomask & HEAP_XMAX_IS_MULTI)
{
/*
* xmax is a multixact, so sanity-check the MXID. Note that we do this
* prior to checking for HEAP_XMAX_INVALID or
* HEAP_XMAX_IS_LOCKED_ONLY. This might therefore complain about
* things that wouldn't actually be a problem during a normal scan,
* but eventually we're going to have to freeze, and that process will
* ignore hint bits.
*
* Even if the MXID is out of range, we still know that the original
* insert committed, so we can check the tuple itself. However, we
* can't rule out the possibility that this tuple is dead, so don't
* clear ctx->tuple_could_be_pruned. Possibly we should go ahead and
* clear that flag anyway if HEAP_XMAX_INVALID is set or if
* HEAP_XMAX_IS_LOCKED_ONLY is true, but for now we err on the side of
* avoiding possibly-bogus complaints about missing TOAST entries.
*/
xmax = HeapTupleHeaderGetRawXmax(tuphdr);
switch (check_mxid_valid_in_rel(xmax, ctx))
{
case XID_INVALID:
report_corruption(ctx,
pstrdup("multitransaction ID is invalid"));
return true;
case XID_PRECEDES_RELMIN:
report_corruption(ctx,
psprintf("multitransaction ID %u precedes relation minimum multitransaction ID threshold %u",
xmax, ctx->relminmxid));
return true;
case XID_PRECEDES_CLUSTERMIN:
report_corruption(ctx,
psprintf("multitransaction ID %u precedes oldest valid multitransaction ID threshold %u",
xmax, ctx->oldest_mxact));
return true;
case XID_IN_FUTURE:
report_corruption(ctx,
psprintf("multitransaction ID %u equals or exceeds next valid multitransaction ID %u",
xmax,
ctx->next_mxact));
return true;
case XID_BOUNDS_OK:
break;
}
}
if (tuphdr->t_infomask & HEAP_XMAX_INVALID)
{
/*
* This tuple is live. A concurrently running transaction could
* delete it before we get around to checking the toast, but any such
* running transaction is surely not less than our safe_xmin, so the
* toast cannot be vacuumed out from under us.
*/
ctx->tuple_could_be_pruned = false;
return true;
}
if (HEAP_XMAX_IS_LOCKED_ONLY(tuphdr->t_infomask))
{
/*
* "Deleting" xact really only locked it, so the tuple is live in any
* case. As above, a concurrently running transaction could delete
* it, but it cannot be vacuumed out from under us.
*/
ctx->tuple_could_be_pruned = false;
return true;
}
if (tuphdr->t_infomask & HEAP_XMAX_IS_MULTI)
{
/*
* We already checked above that this multixact is within limits for
* this table. Now check the update xid from this multixact.
*/
xmax = HeapTupleGetUpdateXid(tuphdr);
switch (get_xid_status(xmax, ctx, &xmax_status))
{
case XID_INVALID:
/* not LOCKED_ONLY, so it has to have an xmax */
report_corruption(ctx,
pstrdup("update xid is invalid"));
return true;
case XID_IN_FUTURE:
report_corruption(ctx,
psprintf("update xid %u equals or exceeds next valid transaction ID %u:%u",
xmax,
EpochFromFullTransactionId(ctx->next_fxid),
XidFromFullTransactionId(ctx->next_fxid)));
return true;
case XID_PRECEDES_RELMIN:
report_corruption(ctx,
psprintf("update xid %u precedes relation freeze threshold %u:%u",
xmax,
EpochFromFullTransactionId(ctx->relfrozenfxid),
XidFromFullTransactionId(ctx->relfrozenfxid)));
return true;
case XID_PRECEDES_CLUSTERMIN:
report_corruption(ctx,
psprintf("update xid %u precedes oldest valid transaction ID %u:%u",
xmax,
EpochFromFullTransactionId(ctx->oldest_fxid),
XidFromFullTransactionId(ctx->oldest_fxid)));
return true;
case XID_BOUNDS_OK:
break;
}
switch (xmax_status)
{
case XID_IS_CURRENT_XID:
case XID_IN_PROGRESS:
/*
* The delete is in progress, so it cannot be visible to our
* snapshot.
*/
ctx->tuple_could_be_pruned = false;
break;
case XID_COMMITTED:
/*
* The delete committed. Whether the toast can be vacuumed
* away depends on how old the deleting transaction is.
*/
ctx->tuple_could_be_pruned = TransactionIdPrecedes(xmax,
ctx->safe_xmin);
break;
case XID_ABORTED:
/*
* The delete aborted or crashed. The tuple is still live.
*/
ctx->tuple_could_be_pruned = false;
break;
}
/* Tuple itself is checkable even if it's dead. */
return true;
}
/* xmax is an XID, not a MXID. Sanity check it. */
xmax = HeapTupleHeaderGetRawXmax(tuphdr);
switch (get_xid_status(xmax, ctx, &xmax_status))
{
case XID_INVALID:
ctx->tuple_could_be_pruned = false;
return true;
case XID_IN_FUTURE:
report_corruption(ctx,
psprintf("xmax %u equals or exceeds next valid transaction ID %u:%u",
xmax,
EpochFromFullTransactionId(ctx->next_fxid),
XidFromFullTransactionId(ctx->next_fxid)));
return false; /* corrupt */
case XID_PRECEDES_RELMIN:
report_corruption(ctx,
psprintf("xmax %u precedes relation freeze threshold %u:%u",
xmax,
EpochFromFullTransactionId(ctx->relfrozenfxid),
XidFromFullTransactionId(ctx->relfrozenfxid)));
return false; /* corrupt */
case XID_PRECEDES_CLUSTERMIN:
report_corruption(ctx,
psprintf("xmax %u precedes oldest valid transaction ID %u:%u",
xmax,
EpochFromFullTransactionId(ctx->oldest_fxid),
XidFromFullTransactionId(ctx->oldest_fxid)));
return false; /* corrupt */
case XID_BOUNDS_OK:
break;
}
/*
* Whether the toast can be vacuumed away depends on how old the deleting
* transaction is.
*/
switch (xmax_status)
{
case XID_IS_CURRENT_XID:
case XID_IN_PROGRESS:
/*
* The delete is in progress, so it cannot be visible to our
* snapshot.
*/
ctx->tuple_could_be_pruned = false;
break;
case XID_COMMITTED:
/*
* The delete committed. Whether the toast can be vacuumed away
* depends on how old the deleting transaction is.
*/
ctx->tuple_could_be_pruned = TransactionIdPrecedes(xmax,
ctx->safe_xmin);
break;
case XID_ABORTED:
/*
* The delete aborted or crashed. The tuple is still live.
*/
ctx->tuple_could_be_pruned = false;
break;
}
/* Tuple itself is checkable even if it's dead. */
return true;
}
/*
* Check the current toast tuple against the state tracked in ctx, recording
* any corruption found in ctx->tupstore.
*
* This is not equivalent to running verify_heapam on the toast table itself,
* and is not hardened against corruption of the toast table. Rather, when
* validating a toasted attribute in the main table, the sequence of toast
* tuples that store the toasted value are retrieved and checked in order, with
* each toast tuple being checked against where we are in the sequence, as well
* as each toast tuple having its varlena structure sanity checked.
*
* On entry, *expected_chunk_seq should be the chunk_seq value that we expect
* to find in toasttup. On exit, it will be updated to the value the next call
* to this function should expect to see.
*/
static void
check_toast_tuple(HeapTuple toasttup, HeapCheckContext *ctx,
ToastedAttribute *ta, int32 *expected_chunk_seq,
uint32 extsize)
{
int32 chunk_seq;
int32 last_chunk_seq = (extsize - 1) / TOAST_MAX_CHUNK_SIZE;
Pointer chunk;
bool isnull;
int32 chunksize;
int32 expected_size;
/* Sanity-check the sequence number. */
chunk_seq = DatumGetInt32(fastgetattr(toasttup, 2,
ctx->toast_rel->rd_att, &isnull));
if (isnull)
{
report_toast_corruption(ctx, ta,
psprintf("toast value %u has toast chunk with null sequence number",
ta->toast_pointer.va_valueid));
return;
}
if (chunk_seq != *expected_chunk_seq)
{
/* Either the TOAST index is corrupt, or we don't have all chunks. */
report_toast_corruption(ctx, ta,
psprintf("toast value %u index scan returned chunk %d when expecting chunk %d",
ta->toast_pointer.va_valueid,
chunk_seq, *expected_chunk_seq));
}
*expected_chunk_seq = chunk_seq + 1;
/* Sanity-check the chunk data. */
chunk = DatumGetPointer(fastgetattr(toasttup, 3,
ctx->toast_rel->rd_att, &isnull));
if (isnull)
{
report_toast_corruption(ctx, ta,
psprintf("toast value %u chunk %d has null data",
ta->toast_pointer.va_valueid,
chunk_seq));
return;
}
if (!VARATT_IS_EXTENDED(chunk))
chunksize = VARSIZE(chunk) - VARHDRSZ;
else if (VARATT_IS_SHORT(chunk))
{
/*
* could happen due to heap_form_tuple doing its thing
*/
chunksize = VARSIZE_SHORT(chunk) - VARHDRSZ_SHORT;
}
else
{
/* should never happen */
uint32 header = ((varattrib_4b *) chunk)->va_4byte.va_header;
report_toast_corruption(ctx, ta,
psprintf("toast value %u chunk %d has invalid varlena header %0x",
ta->toast_pointer.va_valueid,
chunk_seq, header));
return;
}
/*
* Some checks on the data we've found
*/
if (chunk_seq > last_chunk_seq)
{
report_toast_corruption(ctx, ta,
psprintf("toast value %u chunk %d follows last expected chunk %d",
ta->toast_pointer.va_valueid,
chunk_seq, last_chunk_seq));
return;
}
expected_size = chunk_seq < last_chunk_seq ? TOAST_MAX_CHUNK_SIZE
: extsize - (last_chunk_seq * TOAST_MAX_CHUNK_SIZE);
if (chunksize != expected_size)
report_toast_corruption(ctx, ta,
psprintf("toast value %u chunk %d has size %u, but expected size %u",
ta->toast_pointer.va_valueid,
chunk_seq, chunksize, expected_size));
}
/*
* Check the current attribute as tracked in ctx, recording any corruption
* found in ctx->tupstore.
*
* This function follows the logic performed by heap_deform_tuple(), and in the
* case of a toasted value, optionally stores the toast pointer so later it can
* be checked following the logic of detoast_external_attr(), checking for any
* conditions that would result in either of those functions Asserting or
* crashing the backend. The checks performed by Asserts present in those two
* functions are also performed here and in check_toasted_attribute. In cases
* where those two functions are a bit cavalier in their assumptions about data
* being correct, we perform additional checks not present in either of those
* two functions. Where some condition is checked in both of those functions,
* we perform it here twice, as we parallel the logical flow of those two
* functions. The presence of duplicate checks seems a reasonable price to pay
* for keeping this code tightly coupled with the code it protects.
*
* Returns true if the tuple attribute is sane enough for processing to
* continue on to the next attribute, false otherwise.
*/
static bool
check_tuple_attribute(HeapCheckContext *ctx)
{
Datum attdatum;
struct varlena *attr;
char *tp; /* pointer to the tuple data */
uint16 infomask;
CompactAttribute *thisatt;
struct varatt_external toast_pointer;
infomask = ctx->tuphdr->t_infomask;
thisatt = TupleDescCompactAttr(RelationGetDescr(ctx->rel), ctx->attnum);
tp = (char *) ctx->tuphdr + ctx->tuphdr->t_hoff;
if (ctx->tuphdr->t_hoff + ctx->offset > ctx->lp_len)
{
report_corruption(ctx,
psprintf("attribute with length %u starts at offset %u beyond total tuple length %u",
thisatt->attlen,
ctx->tuphdr->t_hoff + ctx->offset,
ctx->lp_len));
return false;
}
/* Skip null values */
if (infomask & HEAP_HASNULL && att_isnull(ctx->attnum, ctx->tuphdr->t_bits))
return true;
/* Skip non-varlena values, but update offset first */
if (thisatt->attlen != -1)
{
ctx->offset = att_nominal_alignby(ctx->offset, thisatt->attalignby);
ctx->offset = att_addlength_pointer(ctx->offset, thisatt->attlen,
tp + ctx->offset);
if (ctx->tuphdr->t_hoff + ctx->offset > ctx->lp_len)
{
report_corruption(ctx,
psprintf("attribute with length %u ends at offset %u beyond total tuple length %u",
thisatt->attlen,
ctx->tuphdr->t_hoff + ctx->offset,
ctx->lp_len));
return false;
}
return true;
}
/* Ok, we're looking at a varlena attribute. */
ctx->offset = att_pointer_alignby(ctx->offset, thisatt->attalignby, -1,
tp + ctx->offset);
/* Get the (possibly corrupt) varlena datum */
attdatum = fetchatt(thisatt, tp + ctx->offset);
/*
* We have the datum, but we cannot decode it carelessly, as it may still
* be corrupt.
*/
/*
* Check that VARTAG_SIZE won't hit an Assert on a corrupt va_tag before
* risking a call into att_addlength_pointer
*/
if (VARATT_IS_EXTERNAL(tp + ctx->offset))
{
uint8 va_tag = VARTAG_EXTERNAL(tp + ctx->offset);
if (va_tag != VARTAG_ONDISK)
{
report_corruption(ctx,
psprintf("toasted attribute has unexpected TOAST tag %u",
va_tag));
/* We can't know where the next attribute begins */
return false;
}
}
/* Ok, should be safe now */
ctx->offset = att_addlength_pointer(ctx->offset, thisatt->attlen,
tp + ctx->offset);
if (ctx->tuphdr->t_hoff + ctx->offset > ctx->lp_len)
{
report_corruption(ctx,
psprintf("attribute with length %u ends at offset %u beyond total tuple length %u",
thisatt->attlen,
ctx->tuphdr->t_hoff + ctx->offset,
ctx->lp_len));
return false;
}
/*
* heap_deform_tuple would be done with this attribute at this point,
* having stored it in values[], and would continue to the next attribute.
* We go further, because we need to check if the toast datum is corrupt.
*/
attr = (struct varlena *) DatumGetPointer(attdatum);
/*
* Now we follow the logic of detoast_external_attr(), with the same
* caveats about being paranoid about corruption.
*/
/* Skip values that are not external */
if (!VARATT_IS_EXTERNAL(attr))
return true;
/* It is external, and we're looking at a page on disk */
/*
* Must copy attr into toast_pointer for alignment considerations
*/
VARATT_EXTERNAL_GET_POINTER(toast_pointer, attr);
/* Toasted attributes too large to be untoasted should never be stored */
if (toast_pointer.va_rawsize > VARLENA_SIZE_LIMIT)
report_corruption(ctx,
psprintf("toast value %u rawsize %d exceeds limit %d",
toast_pointer.va_valueid,
toast_pointer.va_rawsize,
VARLENA_SIZE_LIMIT));
if (VARATT_EXTERNAL_IS_COMPRESSED(toast_pointer))
{
ToastCompressionId cmid;
bool valid = false;
/* Compressed attributes should have a valid compression method */
cmid = TOAST_COMPRESS_METHOD(&toast_pointer);
switch (cmid)
{
/* List of all valid compression method IDs */
case TOAST_PGLZ_COMPRESSION_ID:
case TOAST_LZ4_COMPRESSION_ID:
valid = true;
break;
/* Recognized but invalid compression method ID */
case TOAST_INVALID_COMPRESSION_ID:
break;
/* Intentionally no default here */
}
if (!valid)
report_corruption(ctx,
psprintf("toast value %u has invalid compression method id %d",
toast_pointer.va_valueid, cmid));
}
/* The tuple header better claim to contain toasted values */
if (!(infomask & HEAP_HASEXTERNAL))
{
report_corruption(ctx,
psprintf("toast value %u is external but tuple header flag HEAP_HASEXTERNAL not set",
toast_pointer.va_valueid));
return true;
}
/* The relation better have a toast table */
if (!ctx->rel->rd_rel->reltoastrelid)
{
report_corruption(ctx,
psprintf("toast value %u is external but relation has no toast relation",
toast_pointer.va_valueid));
return true;
}
/* If we were told to skip toast checking, then we're done. */
if (ctx->toast_rel == NULL)
return true;
/*
* If this tuple is eligible to be pruned, we cannot check the toast.
* Otherwise, we push a copy of the toast tuple so we can check it after
* releasing the main table buffer lock.
*/
if (!ctx->tuple_could_be_pruned)
{
ToastedAttribute *ta;
ta = (ToastedAttribute *) palloc0(sizeof(ToastedAttribute));
VARATT_EXTERNAL_GET_POINTER(ta->toast_pointer, attr);
ta->blkno = ctx->blkno;
ta->offnum = ctx->offnum;
ta->attnum = ctx->attnum;
ctx->toasted_attributes = lappend(ctx->toasted_attributes, ta);
}
return true;
}
/*
* For each attribute collected in ctx->toasted_attributes, look up the value
* in the toast table and perform checks on it. This function should only be
* called on toast pointers which cannot be vacuumed away during our
* processing.
*/
static void
check_toasted_attribute(HeapCheckContext *ctx, ToastedAttribute *ta)
{
ScanKeyData toastkey;
SysScanDesc toastscan;
bool found_toasttup;
HeapTuple toasttup;
uint32 extsize;
int32 expected_chunk_seq = 0;
int32 last_chunk_seq;
extsize = VARATT_EXTERNAL_GET_EXTSIZE(ta->toast_pointer);
last_chunk_seq = (extsize - 1) / TOAST_MAX_CHUNK_SIZE;
/*
* Setup a scan key to find chunks in toast table with matching va_valueid
*/
ScanKeyInit(&toastkey,
(AttrNumber) 1,
BTEqualStrategyNumber, F_OIDEQ,
ObjectIdGetDatum(ta->toast_pointer.va_valueid));
/*
* Check if any chunks for this toasted object exist in the toast table,
* accessible via the index.
*/
toastscan = systable_beginscan_ordered(ctx->toast_rel,
ctx->valid_toast_index,
get_toast_snapshot(), 1,
&toastkey);
found_toasttup = false;
while ((toasttup =
systable_getnext_ordered(toastscan,
ForwardScanDirection)) != NULL)
{
found_toasttup = true;
check_toast_tuple(toasttup, ctx, ta, &expected_chunk_seq, extsize);
}
systable_endscan_ordered(toastscan);
if (!found_toasttup)
report_toast_corruption(ctx, ta,
psprintf("toast value %u not found in toast table",
ta->toast_pointer.va_valueid));
else if (expected_chunk_seq <= last_chunk_seq)
report_toast_corruption(ctx, ta,
psprintf("toast value %u was expected to end at chunk %d, but ended while expecting chunk %d",
ta->toast_pointer.va_valueid,
last_chunk_seq, expected_chunk_seq));
}
/*
* Check the current tuple as tracked in ctx, recording any corruption found in
* ctx->tupstore.
*
* We return some information about the status of xmin to aid in validating
* update chains.
*/
static void
check_tuple(HeapCheckContext *ctx, bool *xmin_commit_status_ok,
XidCommitStatus *xmin_commit_status)
{
/*
* Check various forms of tuple header corruption, and if the header is
* too corrupt, do not continue with other checks.
*/
if (!check_tuple_header(ctx))
return;
/*
* Check tuple visibility. If the inserting transaction aborted, we
* cannot assume our relation description matches the tuple structure, and
* therefore cannot check it.
*/
if (!check_tuple_visibility(ctx, xmin_commit_status_ok,
xmin_commit_status))
return;
/*
* The tuple is visible, so it must be compatible with the current version
* of the relation descriptor. It might have fewer columns than are
* present in the relation descriptor, but it cannot have more.
*/
if (RelationGetDescr(ctx->rel)->natts < ctx->natts)
{
report_corruption(ctx,
psprintf("number of attributes %u exceeds maximum expected for table %u",
ctx->natts,
RelationGetDescr(ctx->rel)->natts));
return;
}
/*
* Check each attribute unless we hit corruption that confuses what to do
* next, at which point we abort further attribute checks for this tuple.
* Note that we don't abort for all types of corruption, only for those
* types where we don't know how to continue. We also don't abort the
* checking of toasted attributes collected from the tuple prior to
* aborting. Those will still be checked later along with other toasted
* attributes collected from the page.
*/
ctx->offset = 0;
for (ctx->attnum = 0; ctx->attnum < ctx->natts; ctx->attnum++)
if (!check_tuple_attribute(ctx))
break; /* cannot continue */
/* revert attnum to -1 until we again examine individual attributes */
ctx->attnum = -1;
}
/*
* Convert a TransactionId into a FullTransactionId using our cached values of
* the valid transaction ID range. It is the caller's responsibility to have
* already updated the cached values, if necessary. This is akin to
* FullTransactionIdFromAllowableAt(), but it tolerates corruption in the form
* of an xid before epoch 0.
*/
static FullTransactionId
FullTransactionIdFromXidAndCtx(TransactionId xid, const HeapCheckContext *ctx)
{
uint64 nextfxid_i;
int32 diff;
FullTransactionId fxid;
Assert(TransactionIdIsNormal(ctx->next_xid));
Assert(FullTransactionIdIsNormal(ctx->next_fxid));
Assert(XidFromFullTransactionId(ctx->next_fxid) == ctx->next_xid);
if (!TransactionIdIsNormal(xid))
return FullTransactionIdFromEpochAndXid(0, xid);
nextfxid_i = U64FromFullTransactionId(ctx->next_fxid);
/* compute the 32bit modulo difference */
diff = (int32) (ctx->next_xid - xid);
/*
* In cases of corruption we might see a 32bit xid that is before epoch 0.
* We can't represent that as a 64bit xid, due to 64bit xids being
* unsigned integers, without the modulo arithmetic of 32bit xid. There's
* no really nice way to deal with that, but it works ok enough to use
* FirstNormalFullTransactionId in that case, as a freshly initdb'd
* cluster already has a newer horizon.
*/
if (diff > 0 && (nextfxid_i - FirstNormalTransactionId) < (int64) diff)
{
Assert(EpochFromFullTransactionId(ctx->next_fxid) == 0);
fxid = FirstNormalFullTransactionId;
}
else
fxid = FullTransactionIdFromU64(nextfxid_i - diff);
Assert(FullTransactionIdIsNormal(fxid));
return fxid;
}
/*
* Update our cached range of valid transaction IDs.
*/
static void
update_cached_xid_range(HeapCheckContext *ctx)
{
/* Make cached copies */
LWLockAcquire(XidGenLock, LW_SHARED);
ctx->next_fxid = TransamVariables->nextXid;
ctx->oldest_xid = TransamVariables->oldestXid;
LWLockRelease(XidGenLock);
/* And compute alternate versions of the same */
ctx->next_xid = XidFromFullTransactionId(ctx->next_fxid);
ctx->oldest_fxid = FullTransactionIdFromXidAndCtx(ctx->oldest_xid, ctx);
}
/*
* Update our cached range of valid multitransaction IDs.
*/
static void
update_cached_mxid_range(HeapCheckContext *ctx)
{
ReadMultiXactIdRange(&ctx->oldest_mxact, &ctx->next_mxact);
}
/*
* Return whether the given FullTransactionId is within our cached valid
* transaction ID range.
*/
static inline bool
fxid_in_cached_range(FullTransactionId fxid, const HeapCheckContext *ctx)
{
return (FullTransactionIdPrecedesOrEquals(ctx->oldest_fxid, fxid) &&
FullTransactionIdPrecedes(fxid, ctx->next_fxid));
}
/*
* Checks whether a multitransaction ID is in the cached valid range, returning
* the nature of the range violation, if any.
*/
static XidBoundsViolation
check_mxid_in_range(MultiXactId mxid, HeapCheckContext *ctx)
{
if (!TransactionIdIsValid(mxid))
return XID_INVALID;
if (MultiXactIdPrecedes(mxid, ctx->relminmxid))
return XID_PRECEDES_RELMIN;
if (MultiXactIdPrecedes(mxid, ctx->oldest_mxact))
return XID_PRECEDES_CLUSTERMIN;
if (MultiXactIdPrecedesOrEquals(ctx->next_mxact, mxid))
return XID_IN_FUTURE;
return XID_BOUNDS_OK;
}
/*
* Checks whether the given mxid is valid to appear in the heap being checked,
* returning the nature of the range violation, if any.
*
* This function attempts to return quickly by caching the known valid mxid
* range in ctx. Callers should already have performed the initial setup of
* the cache prior to the first call to this function.
*/
static XidBoundsViolation
check_mxid_valid_in_rel(MultiXactId mxid, HeapCheckContext *ctx)
{
XidBoundsViolation result;
result = check_mxid_in_range(mxid, ctx);
if (result == XID_BOUNDS_OK)
return XID_BOUNDS_OK;
/* The range may have advanced. Recheck. */
update_cached_mxid_range(ctx);
return check_mxid_in_range(mxid, ctx);
}
/*
* Checks whether the given transaction ID is (or was recently) valid to appear
* in the heap being checked, or whether it is too old or too new to appear in
* the relation, returning information about the nature of the bounds violation.
*
* We cache the range of valid transaction IDs. If xid is in that range, we
* conclude that it is valid, even though concurrent changes to the table might
* invalidate it under certain corrupt conditions. (For example, if the table
* contains corrupt all-frozen bits, a concurrent vacuum might skip the page(s)
* containing the xid and then truncate clog and advance the relfrozenxid
* beyond xid.) Reporting the xid as valid under such conditions seems
* acceptable, since if we had checked it earlier in our scan it would have
* truly been valid at that time.
*
* If the status argument is not NULL, and if and only if the transaction ID
* appears to be valid in this relation, the status argument will be set with
* the commit status of the transaction ID.
*/
static XidBoundsViolation
get_xid_status(TransactionId xid, HeapCheckContext *ctx,
XidCommitStatus *status)
{
FullTransactionId fxid;
FullTransactionId clog_horizon;
/* Quick check for special xids */
if (!TransactionIdIsValid(xid))
return XID_INVALID;
else if (xid == BootstrapTransactionId || xid == FrozenTransactionId)
{
if (status != NULL)
*status = XID_COMMITTED;
return XID_BOUNDS_OK;
}
/* Check if the xid is within bounds */
fxid = FullTransactionIdFromXidAndCtx(xid, ctx);
if (!fxid_in_cached_range(fxid, ctx))
{
/*
* We may have been checking against stale values. Update the cached
* range to be sure, and since we relied on the cached range when we
* performed the full xid conversion, reconvert.
*/
update_cached_xid_range(ctx);
fxid = FullTransactionIdFromXidAndCtx(xid, ctx);
}
if (FullTransactionIdPrecedesOrEquals(ctx->next_fxid, fxid))
return XID_IN_FUTURE;
if (FullTransactionIdPrecedes(fxid, ctx->oldest_fxid))
return XID_PRECEDES_CLUSTERMIN;
if (FullTransactionIdPrecedes(fxid, ctx->relfrozenfxid))
return XID_PRECEDES_RELMIN;
/* Early return if the caller does not request clog checking */
if (status == NULL)
return XID_BOUNDS_OK;
/* Early return if we just checked this xid in a prior call */
if (xid == ctx->cached_xid)
{
*status = ctx->cached_status;
return XID_BOUNDS_OK;
}
*status = XID_COMMITTED;
LWLockAcquire(XactTruncationLock, LW_SHARED);
clog_horizon =
FullTransactionIdFromXidAndCtx(TransamVariables->oldestClogXid,
ctx);
if (FullTransactionIdPrecedesOrEquals(clog_horizon, fxid))
{
if (TransactionIdIsCurrentTransactionId(xid))
*status = XID_IS_CURRENT_XID;
else if (TransactionIdIsInProgress(xid))
*status = XID_IN_PROGRESS;
else if (TransactionIdDidCommit(xid))
*status = XID_COMMITTED;
else
*status = XID_ABORTED;
}
LWLockRelease(XactTruncationLock);
ctx->cached_xid = xid;
ctx->cached_status = *status;
return XID_BOUNDS_OK;
}
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