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Fix PageAddItem BRIN bug

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BRIN was relying on the ability to remove a tuple from an index page,
then putting another tuple in the same line pointer.  But PageAddItem
refuses to add a tuple beyond the first free item past the last used
item, and in particular, it rejects an attempt to add an item to an
empty page anywhere other than the first line pointer.  PageAddItem
issues a WARNING and indicates to the caller that it failed, which in
turn causes the BRIN calling code to issue a PANIC, so the whole
sequence looks like this:
	WARNING:  specified item offset is too large
	PANIC:  failed to add BRIN tuple

To fix, create a new function PageAddItemExtended which is like
PageAddItem except that the two boolean arguments become a flags bitmap;
the "overwrite" and "is_heap" boolean flags in PageAddItem become
PAI_OVERWITE and PAI_IS_HEAP flags in the new function, and a new flag
PAI_ALLOW_FAR_OFFSET enables the behavior required by BRIN.
PageAddItem() retains its original signature, for compatibility with
third-party modules (other callers in core code are not modified,
either).

Also, in the belt-and-suspenders spirit, I added a new sanity check in
brinGetTupleForHeapBlock to raise an error if an TID found in the revmap
is not marked as live by the page header.  This causes it to react with
"ERROR: corrupted BRIN index" to the bug at hand, rather than a hard
crash.

Backpatch to 9.5.

Bug reported by Andreas Seltenreich as detected by his handy sqlsmith
fuzzer.
Discussion: https://www.postgresql.org/message-id/87mvni77jh.fsf@elite.ansel.ydns.eu
This commit is contained in:
Alvaro Herrera
2016-05-30 14:47:22 -04:00
parent 3c8aa6654a
commit 975ad4e602
5 changed files with 60 additions and 18 deletions
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5
src/include/storage/bufpage.h
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@@ -407,11 +407,16 @@ do { \
* extern declarations
* ----------------------------------------------------------------
*/
#define PAI_OVERWRITE (1 << 0)
#define PAI_IS_HEAP (1 << 1)
#define PAI_ALLOW_FAR_OFFSET (1 << 2)
extern void PageInit(Page page, Size pageSize, Size specialSize);
extern bool PageIsVerified(Page page, BlockNumber blkno);
extern OffsetNumber PageAddItem(Page page, Item item, Size size,
OffsetNumber offsetNumber, bool overwrite, bool is_heap);
extern OffsetNumber PageAddItemExtended(Page page, Item item, Size size,
OffsetNumber offsetNumber, int flags);
extern Page PageGetTempPage(Page page);
extern Page PageGetTempPageCopy(Page page);
extern Page PageGetTempPageCopySpecial(Page page);