/*
* Redo function for generic xlog record.
*/
void
generic_redo(XLogReaderState *record)
{
XLogRecPtr lsn = record->EndRecPtr;
Buffer buffers[MAX_GENERIC_XLOG_PAGES];
uint8 block_id;
/* Protect limited size of buffers[] array */
Assert(record->max_block_id < MAX_GENERIC_XLOG_PAGES);
/* Iterate over blocks */
for (block_id = 0; block_id <= record->max_block_id; block_id++)
{
XLogRedoAction action;
if (!XLogRecHasBlockRef(record, block_id))
{
buffers[block_id] = InvalidBuffer;
continue;
}
action = XLogReadBufferForRedo(record, block_id, &buffers[block_id]);
/* Apply redo to given block if needed */
if (action == BLK_NEEDS_REDO)
{
Page page;
PageHeader pageHeader;
char *blockDelta;
Size blockDeltaSize;
page = BufferGetPage(buffers[block_id], NULL, NULL,
BGP_NO_SNAPSHOT_TEST);
blockDelta = XLogRecGetBlockData(record, block_id, &blockDeltaSize);
applyPageRedo(page, blockDelta, blockDeltaSize);
/*
* Since the delta contains no information about what's in the
* "hole" between pd_lower and pd_upper, set that to zero to
* ensure we produce the same page state that application of the
* logged action by GenericXLogFinish did.
*/
pageHeader = (PageHeader) page;
memset(page + pageHeader->pd_lower, 0,
pageHeader->pd_upper - pageHeader->pd_lower);
PageSetLSN(page, lsn);
MarkBufferDirty(buffers[block_id]);
}
}
/* Changes are done: unlock and release all buffers */
for (block_id = 0; block_id <= record->max_block_id; block_id++)
{
if (BufferIsValid(buffers[block_id]))
UnlockReleaseBuffer(buffers[block_id]);
}
}
/*
* Compute the XLOG delta record needed to transform curpage into targetpage,
* and store it in pageData's delta field.
*/
static void
computeDelta(PageData *pageData, Page curpage, Page targetpage)
{
int targetLower = ((PageHeader) targetpage)->pd_lower,
targetUpper = ((PageHeader) targetpage)->pd_upper,
curLower = ((PageHeader) curpage)->pd_lower,
curUpper = ((PageHeader) curpage)->pd_upper;
pageData->deltaLen = 0;
/* Compute delta records for lower part of page ... */
computeRegionDelta(pageData, curpage, targetpage,
0, targetLower,
0, curLower);
/* ... and for upper part, ignoring what's between */
computeRegionDelta(pageData, curpage, targetpage,
targetUpper, BLCKSZ,
curUpper, BLCKSZ);
/*
* If xlog debug is enabled, then check produced delta. Result of delta
* application to curpage should be equivalent to targetpage.
*/
#ifdef WAL_DEBUG
if (XLOG_DEBUG)
{
char tmp[BLCKSZ];
memcpy(tmp, curpage, BLCKSZ);
applyPageRedo(tmp, pageData->delta, pageData->deltaLen);
if (memcmp(tmp, targetpage, targetLower) != 0 ||
memcmp(tmp + targetUpper, targetpage + targetUpper,
BLCKSZ - targetUpper) != 0)
elog(ERROR, "result of generic xlog apply does not match");
}
#endif
}
