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Simplify hash_xlog_split_allocate_page()

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Instead of complicated pointer arithmetic, overlay a uint32 array and
just access the array members.  That's safe thanks to
XLogRecGetBlockData() returning a MAXALIGNed buffer.

Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Discussion: https://www.postgresql.org/message-id/flat/aSQy2JawavlVlEB0%40ip-10-97-1-34.eu-west-3.compute.internal
This commit is contained in:
Peter Eisentraut 2025-12-02 09:10:02 +01:00
parent ec782f56b0
commit 35988b31db
1 changed files with 17 additions and 18 deletions
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35
src/backend/access/hash/hash_xlog.c
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@ -314,8 +314,6 @@ hash_xlog_split_allocate_page(XLogReaderState *record)
Buffer oldbuf; Buffer oldbuf;
Buffer newbuf; Buffer newbuf;
Buffer metabuf; Buffer metabuf;
Size datalen PG_USED_FOR_ASSERTS_ONLY;
char *data;
XLogRedoAction action; XLogRedoAction action;
/* /*
@ -375,6 +373,10 @@ hash_xlog_split_allocate_page(XLogReaderState *record)
{ {
Page page; Page page;
HashMetaPage metap; HashMetaPage metap;
Size datalen;
char *data;
uint32 *uidata;
int uidatacount;
page = BufferGetPage(metabuf); page = BufferGetPage(metabuf);
metap = HashPageGetMeta(page); metap = HashPageGetMeta(page);
@ -382,34 +384,31 @@ hash_xlog_split_allocate_page(XLogReaderState *record)
data = XLogRecGetBlockData(record, 2, &datalen); data = XLogRecGetBlockData(record, 2, &datalen);
/*
* This cast is ok because XLogRecGetBlockData() returns a MAXALIGNed
* buffer.
*/
uidata = (uint32 *) data;
uidatacount = 0;
if (xlrec->flags & XLH_SPLIT_META_UPDATE_MASKS) if (xlrec->flags & XLH_SPLIT_META_UPDATE_MASKS)
{ {
uint32 lowmask; uint32 lowmask = uidata[uidatacount++];
uint32 *highmask; uint32 highmask = uidata[uidatacount++];
/* extract low and high masks. */
memcpy(&lowmask, data, sizeof(uint32));
highmask = (uint32 *) ((char *) data + sizeof(uint32));
/* update metapage */ /* update metapage */
metap->hashm_lowmask = lowmask; metap->hashm_lowmask = lowmask;
metap->hashm_highmask = *highmask; metap->hashm_highmask = highmask;
data += sizeof(uint32) * 2;
} }
if (xlrec->flags & XLH_SPLIT_META_UPDATE_SPLITPOINT) if (xlrec->flags & XLH_SPLIT_META_UPDATE_SPLITPOINT)
{ {
uint32 ovflpoint; uint32 ovflpoint = uidata[uidatacount++];
uint32 *ovflpages; uint32 ovflpages = uidata[uidatacount++];
/* extract information of overflow pages. */
memcpy(&ovflpoint, data, sizeof(uint32));
ovflpages = (uint32 *) ((char *) data + sizeof(uint32));
/* update metapage */ /* update metapage */
metap->hashm_spares[ovflpoint] = *ovflpages;
metap->hashm_ovflpoint = ovflpoint; metap->hashm_ovflpoint = ovflpoint;
metap->hashm_spares[ovflpoint] = ovflpages;
} }
MarkBufferDirty(metabuf); MarkBufferDirty(metabuf);