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pg_walinspect: Add pg_get_wal_fpi_info()

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This function is able to extract the full page images from a range of
records, specified as of input arguments start_lsn and end_lsn.  Like
the other functions of this module, an error is returned if using LSNs
that do not reflect real system values.  All the FPIs stored in a single
record are extracted.

The module's version is bumped to 1.1.

Author: Bharath Rupireddy
Reviewed-by: Bertrand Drouvot
Discussion: https://postgr.es/m/CALj2ACVCcvzd7WiWvD=6_7NBvVB_r6G0EGSxL4F8vosAi6Se4g@mail.gmail.com
This commit is contained in:
Michael Paquier
2023-01-23 13:55:18 +09:00
parent 16fd03e956
commit c31cf1c03d
8 changed files with 245 additions and 4 deletions
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111
contrib/pg_walinspect/pg_walinspect.c
View File

@@ -30,6 +30,7 @@
PG_MODULE_MAGIC;
PG_FUNCTION_INFO_V1(pg_get_wal_fpi_info);
PG_FUNCTION_INFO_V1(pg_get_wal_record_info);
PG_FUNCTION_INFO_V1(pg_get_wal_records_info);
PG_FUNCTION_INFO_V1(pg_get_wal_records_info_till_end_of_wal);
@@ -55,6 +56,7 @@ static void FillXLogStatsRow(const char *name, uint64 n, uint64 total_count,
Datum *values, bool *nulls, uint32 ncols);
static void GetWalStats(FunctionCallInfo fcinfo, XLogRecPtr start_lsn,
XLogRecPtr end_lsn, bool stats_per_record);
static void GetWALFPIInfo(FunctionCallInfo fcinfo, XLogReaderState *record);
/*
* Check if the given LSN is in future. Also, return the LSN up to which the
@@ -217,6 +219,115 @@ GetWALRecordInfo(XLogReaderState *record, Datum *values,
Assert(i == ncols);
}
/*
* Store a set of full page images from a single record.
*/
static void
GetWALFPIInfo(FunctionCallInfo fcinfo, XLogReaderState *record)
{
#define PG_GET_WAL_FPI_INFO_COLS 7
int block_id;
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
for (block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
{
PGAlignedBlock buf;
Page page;
bytea *raw_page;
BlockNumber blk;
RelFileLocator rnode;
ForkNumber fork;
Datum values[PG_GET_WAL_FPI_INFO_COLS] = {0};
bool nulls[PG_GET_WAL_FPI_INFO_COLS] = {0};
int i = 0;
if (!XLogRecHasBlockRef(record, block_id))
continue;
if (!XLogRecHasBlockImage(record, block_id))
continue;
page = (Page) buf.data;
if (!RestoreBlockImage(record, block_id, page))
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg_internal("%s", record->errormsg_buf)));
/* Full page exists, so let's save it. */
(void) XLogRecGetBlockTagExtended(record, block_id,
&rnode, &fork, &blk, NULL);
values[i++] = LSNGetDatum(record->ReadRecPtr);
values[i++] = ObjectIdGetDatum(rnode.spcOid);
values[i++] = ObjectIdGetDatum(rnode.dbOid);
values[i++] = ObjectIdGetDatum(rnode.relNumber);
values[i++] = Int64GetDatum((int64) blk);
if (fork >= 0 && fork <= MAX_FORKNUM)
values[i++] = CStringGetTextDatum(forkNames[fork]);
else
ereport(ERROR,
(errcode(ERRCODE_INTERNAL_ERROR),
errmsg_internal("invalid fork number: %u", fork)));
/* Initialize bytea buffer to copy the FPI to. */
raw_page = (bytea *) palloc(BLCKSZ + VARHDRSZ);
SET_VARSIZE(raw_page, BLCKSZ + VARHDRSZ);
/* Take a verbatim copy of the FPI. */
memcpy(VARDATA(raw_page), page, BLCKSZ);
values[i++] = PointerGetDatum(raw_page);
Assert(i == PG_GET_WAL_FPI_INFO_COLS);
tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
values, nulls);
}
#undef PG_GET_WAL_FPI_INFO_COLS
}
/*
* Get full page images with their relation information for all the WAL
* records between start and end LSNs. Decompression is applied to the
* blocks, if necessary.
*
* This function emits an error if a future start or end WAL LSN i.e. WAL LSN
* the database system doesn't know about is specified.
*/
Datum
pg_get_wal_fpi_info(PG_FUNCTION_ARGS)
{
XLogRecPtr start_lsn;
XLogRecPtr end_lsn;
XLogReaderState *xlogreader;
start_lsn = PG_GETARG_LSN(0);
end_lsn = PG_GETARG_LSN(1);
end_lsn = ValidateInputLSNs(false, start_lsn, end_lsn);
InitMaterializedSRF(fcinfo, 0);
xlogreader = InitXLogReaderState(start_lsn);
while (ReadNextXLogRecord(xlogreader) &&
xlogreader->EndRecPtr <= end_lsn)
{
GetWALFPIInfo(fcinfo, xlogreader);
CHECK_FOR_INTERRUPTS();
}
pfree(xlogreader->private_data);
XLogReaderFree(xlogreader);
PG_RETURN_VOID();
}
/*
* Get WAL record info.
*