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postgres/contrib/pageinspect/ginfuncs.c
Michael Paquier df6bbe73b8 pageinspect: Fix handling of all-zero pages 
Getting from get_raw_page() an all-zero page is considered as a valid
case by the buffer manager and it can happen for example when finding a
corrupted page with zero_damaged_pages enabled (using zero_damaged_pages
to look at corrupted pages happens), or after a crash when a relation
file is extended before any WAL for its new data is generated (before a
vacuum or autovacuum job comes in to do some cleanup).

However, all the functions of pageinspect, as of the index AMs (except
hash that has its own idea of new pages), heap, the FSM or the page
header have never worked with all-zero pages, causing various crashes
when going through the page internals.

This commit changes all the pageinspect functions to be compliant with
all-zero pages, where the choice is made to return NULL or no rows for
SRFs when finding a new page.  get_raw_page() still works the same way,
returning a batch of zeros in the bytea of the page retrieved.  A hard
error could be used but NULL, while more invasive, is useful when
scanning relation files in full to get a batch of results for a single
relation in one query.  Tests are added for all the code paths
impacted.

Reported-by: Daria Lepikhova
Author: Michael Paquier
Discussion: https://postgr.es/m/561e187b-3549-c8d5-03f5-525c14e65bd0@postgrespro.ru
Backpatch-through: 10
2022-04-14 15:09:26 +09:00

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/*
* ginfuncs.c
* Functions to investigate the content of GIN indexes
*
* Copyright (c) 2014-2021, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/pageinspect/ginfuncs.c
*/
#include "postgres.h"
#include "access/gin.h"
#include "access/gin_private.h"
#include "access/htup_details.h"
#include "catalog/namespace.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "pageinspect.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/rel.h"
#define DatumGetItemPointer(X) ((ItemPointer) DatumGetPointer(X))
#define ItemPointerGetDatum(X) PointerGetDatum(X)
PG_FUNCTION_INFO_V1(gin_metapage_info);
PG_FUNCTION_INFO_V1(gin_page_opaque_info);
PG_FUNCTION_INFO_V1(gin_leafpage_items);
Datum
gin_metapage_info(PG_FUNCTION_ARGS)
{
bytea *raw_page = PG_GETARG_BYTEA_P(0);
TupleDesc tupdesc;
Page page;
GinPageOpaque opaq;
GinMetaPageData *metadata;
HeapTuple resultTuple;
Datum values[10];
bool nulls[10];
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to use raw page functions")));
page = get_page_from_raw(raw_page);
if (PageIsNew(page))
PG_RETURN_NULL();
if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GinPageOpaqueData)))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page is not a valid GIN metapage"),
errdetail("Expected special size %d, got %d.",
(int) MAXALIGN(sizeof(GinPageOpaqueData)),
(int) PageGetSpecialSize(page))));
opaq = (GinPageOpaque) PageGetSpecialPointer(page);
if (opaq->flags != GIN_META)
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page is not a GIN metapage"),
errdetail("Flags %04X, expected %04X",
opaq->flags, GIN_META)));
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
metadata = GinPageGetMeta(page);
memset(nulls, 0, sizeof(nulls));
values[0] = Int64GetDatum(metadata->head);
values[1] = Int64GetDatum(metadata->tail);
values[2] = Int32GetDatum(metadata->tailFreeSize);
values[3] = Int64GetDatum(metadata->nPendingPages);
values[4] = Int64GetDatum(metadata->nPendingHeapTuples);
/* statistics, updated by VACUUM */
values[5] = Int64GetDatum(metadata->nTotalPages);
values[6] = Int64GetDatum(metadata->nEntryPages);
values[7] = Int64GetDatum(metadata->nDataPages);
values[8] = Int64GetDatum(metadata->nEntries);
values[9] = Int32GetDatum(metadata->ginVersion);
/* Build and return the result tuple. */
resultTuple = heap_form_tuple(tupdesc, values, nulls);
return HeapTupleGetDatum(resultTuple);
}
Datum
gin_page_opaque_info(PG_FUNCTION_ARGS)
{
bytea *raw_page = PG_GETARG_BYTEA_P(0);
TupleDesc tupdesc;
Page page;
GinPageOpaque opaq;
HeapTuple resultTuple;
Datum values[3];
bool nulls[3];
Datum flags[16];
int nflags = 0;
uint16 flagbits;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to use raw page functions")));
page = get_page_from_raw(raw_page);
if (PageIsNew(page))
PG_RETURN_NULL();
if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GinPageOpaqueData)))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page is not a valid GIN data leaf page"),
errdetail("Expected special size %d, got %d.",
(int) MAXALIGN(sizeof(GinPageOpaqueData)),
(int) PageGetSpecialSize(page))));
opaq = (GinPageOpaque) PageGetSpecialPointer(page);
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
/* Convert the flags bitmask to an array of human-readable names */
flagbits = opaq->flags;
if (flagbits & GIN_DATA)
flags[nflags++] = CStringGetTextDatum("data");
if (flagbits & GIN_LEAF)
flags[nflags++] = CStringGetTextDatum("leaf");
if (flagbits & GIN_DELETED)
flags[nflags++] = CStringGetTextDatum("deleted");
if (flagbits & GIN_META)
flags[nflags++] = CStringGetTextDatum("meta");
if (flagbits & GIN_LIST)
flags[nflags++] = CStringGetTextDatum("list");
if (flagbits & GIN_LIST_FULLROW)
flags[nflags++] = CStringGetTextDatum("list_fullrow");
if (flagbits & GIN_INCOMPLETE_SPLIT)
flags[nflags++] = CStringGetTextDatum("incomplete_split");
if (flagbits & GIN_COMPRESSED)
flags[nflags++] = CStringGetTextDatum("compressed");
flagbits &= ~(GIN_DATA | GIN_LEAF | GIN_DELETED | GIN_META | GIN_LIST |
GIN_LIST_FULLROW | GIN_INCOMPLETE_SPLIT | GIN_COMPRESSED);
if (flagbits)
{
/* any flags we don't recognize are printed in hex */
flags[nflags++] = DirectFunctionCall1(to_hex32, Int32GetDatum(flagbits));
}
memset(nulls, 0, sizeof(nulls));
values[0] = Int64GetDatum(opaq->rightlink);
values[1] = Int32GetDatum(opaq->maxoff);
values[2] = PointerGetDatum(construct_array(flags, nflags,
TEXTOID,
-1, false, TYPALIGN_INT));
/* Build and return the result tuple. */
resultTuple = heap_form_tuple(tupdesc, values, nulls);
return HeapTupleGetDatum(resultTuple);
}
typedef struct gin_leafpage_items_state
{
TupleDesc tupd;
GinPostingList *seg;
GinPostingList *lastseg;
} gin_leafpage_items_state;
Datum
gin_leafpage_items(PG_FUNCTION_ARGS)
{
bytea *raw_page = PG_GETARG_BYTEA_P(0);
FuncCallContext *fctx;
gin_leafpage_items_state *inter_call_data;
if (!superuser())
ereport(ERROR,
(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
errmsg("must be superuser to use raw page functions")));
if (SRF_IS_FIRSTCALL())
{
TupleDesc tupdesc;
MemoryContext mctx;
Page page;
GinPageOpaque opaq;
fctx = SRF_FIRSTCALL_INIT();
mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
page = get_page_from_raw(raw_page);
if (PageIsNew(page))
{
MemoryContextSwitchTo(mctx);
PG_RETURN_NULL();
}
if (PageGetSpecialSize(page) != MAXALIGN(sizeof(GinPageOpaqueData)))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page is not a valid GIN data leaf page"),
errdetail("Expected special size %d, got %d.",
(int) MAXALIGN(sizeof(GinPageOpaqueData)),
(int) PageGetSpecialSize(page))));
opaq = (GinPageOpaque) PageGetSpecialPointer(page);
if (opaq->flags != (GIN_DATA | GIN_LEAF | GIN_COMPRESSED))
ereport(ERROR,
(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
errmsg("input page is not a compressed GIN data leaf page"),
errdetail("Flags %04X, expected %04X",
opaq->flags,
(GIN_DATA | GIN_LEAF | GIN_COMPRESSED))));
inter_call_data = palloc(sizeof(gin_leafpage_items_state));
/* Build a tuple descriptor for our result type */
if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
elog(ERROR, "return type must be a row type");
inter_call_data->tupd = tupdesc;
inter_call_data->seg = GinDataLeafPageGetPostingList(page);
inter_call_data->lastseg = (GinPostingList *)
(((char *) inter_call_data->seg) +
GinDataLeafPageGetPostingListSize(page));
fctx->user_fctx = inter_call_data;
MemoryContextSwitchTo(mctx);
}
fctx = SRF_PERCALL_SETUP();
inter_call_data = fctx->user_fctx;
if (inter_call_data->seg != inter_call_data->lastseg)
{
GinPostingList *cur = inter_call_data->seg;
HeapTuple resultTuple;
Datum result;
Datum values[3];
bool nulls[3];
int ndecoded,
i;
ItemPointer tids;
Datum *tids_datum;
memset(nulls, 0, sizeof(nulls));
values[0] = ItemPointerGetDatum(&cur->first);
values[1] = UInt16GetDatum(cur->nbytes);
/* build an array of decoded item pointers */
tids = ginPostingListDecode(cur, &ndecoded);
tids_datum = (Datum *) palloc(ndecoded * sizeof(Datum));
for (i = 0; i < ndecoded; i++)
tids_datum[i] = ItemPointerGetDatum(&tids[i]);
values[2] = PointerGetDatum(construct_array(tids_datum,
ndecoded,
TIDOID,
sizeof(ItemPointerData),
false, TYPALIGN_SHORT));
pfree(tids_datum);
pfree(tids);
/* Build and return the result tuple. */
resultTuple = heap_form_tuple(inter_call_data->tupd, values, nulls);
result = HeapTupleGetDatum(resultTuple);
inter_call_data->seg = GinNextPostingListSegment(cur);
SRF_RETURN_NEXT(fctx, result);
}
SRF_RETURN_DONE(fctx);
}
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