Re: FSM Corruption (was: Could not read block at end of the relation)

On 3/6/24 10:31, Ronan Dunklau wrote:
> Le mardi 5 mars 2024, 00:05:03 CET Noah Misch a écrit :
>> I would guess this one is more risky from a performance perspective, since
>> we'd be adding to a hotter path under RelationGetBufferForTuple().  Still,
>> it's likely fine.
> 
> I ended up implementing this in the attached patch. The idea is that we detect
> if the FSM returns a page past the end of the relation, and ignore it.
> In that case we will fallback through the extension mechanism.

@@ -582,7 +583,17 @@ RelationGetBufferForTuple(Relation relation, Size len,
  		 * We have no cached target page, so ask the FSM for an initial
  		 * target.
  		 */
+		nblocks = RelationGetNumberOfBlocks(relation);
  		targetBlock = GetPageWithFreeSpace(relation, targetFreeSpace);

I'd move the fetching of nblocks to after getting the targetBlock. This 
avoids extending the relation in the unlikely event of a FSM/relation 
extension in-between those two calls.

Patrick