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commit    984d0a14e8d0141a68da5bd56ce6821042298904
Author:   Tom Lane <tgl@sss.pgh.pa.us>
Date:     Fri Sep 09 16:20:58 2016 +0000
First released in: 10.0

    In PageIndexTupleDelete, don't assume stored item lengths are MAXALIGNed.
    
    PageAddItem stores the item length as-is.  It MAXALIGN's the amount of
    space actually allocated for each tuple, but not the stored length.
    PageRepairFragmentation, PageIndexMultiDelete, and PageIndexDeleteNoCompact
    are all on board with this and MAXALIGN item lengths after fetching them.
    But PageIndexTupleDelete expects the stored length to be a MAXALIGN
    multiple already.  This accidentally works for existing index AMs because
    they all maxalign their tuple sizes internally; but we don't do that for
    heap tuples, and it shouldn't be a requirement for index tuples either.
    
    So, sync PageIndexTupleDelete with the rest of bufpage.c by having it
    maxalign the item size after fetching.
    
    Also add a check that pd_special is maxaligned, to ensure that the test
    "(offset + size) > phdr->pd_special" is still doing the right thing.
    (If offset and pd_special are aligned, it doesn't matter whether size is.)
    Again, this is in sync with the rest of the routines here, except for
    PageAddItem which doesn't test because it doesn't actually do anything
    for which pd_special alignment matters.
    
    This shouldn't have any immediate functional impact; it just adds the
    flexibility to use PageIndexTupleDelete on index tuples with non-aligned
    lengths.
    
    Discussion: <3814.1473366762@sss.pgh.pa.us>


 src/backend/storage/page/bufpage.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/backend/storage/page/bufpage.c b/src/backend/storage/page/bufpage.c
index 1b70bfbe8cc..bce0d53a9c4 100644
--- a/src/backend/storage/page/bufpage.c
+++ b/src/backend/storage/page/bufpage.c
@@ -738,7 +738,8 @@ PageIndexTupleDelete(Page page, OffsetNumber offnum)
 	if (phdr->pd_lower < SizeOfPageHeaderData ||
 		phdr->pd_lower > phdr->pd_upper ||
 		phdr->pd_upper > phdr->pd_special ||
-		phdr->pd_special > BLCKSZ)
+		phdr->pd_special > BLCKSZ ||
+		phdr->pd_special != MAXALIGN(phdr->pd_special))
 		ereport(ERROR,
 				(errcode(ERRCODE_DATA_CORRUPTED),
 				 errmsg("corrupted page pointers: lower = %u, upper = %u, special = %u",
@@ -757,12 +758,15 @@ PageIndexTupleDelete(Page page, OffsetNumber offnum)
 	offset = ItemIdGetOffset(tup);
 
 	if (offset < phdr->pd_upper || (offset + size) > phdr->pd_special ||
-		offset != MAXALIGN(offset) || size != MAXALIGN(size))
+		offset != MAXALIGN(offset))
 		ereport(ERROR,
 				(errcode(ERRCODE_DATA_CORRUPTED),
 				 errmsg("corrupted item pointer: offset = %u, size = %u",
 						offset, (unsigned int) size)));
 
+	/* Amount of space to actually be deleted */
+	size = MAXALIGN(size);
+
 	/*
 	 * First, we want to get rid of the pd_linp entry for the index tuple. We
 	 * copy all subsequent linp's back one slot in the array. We don't use


[parent: e0013deb5983]