Re: Relation extension scalability

1.

+GetPageWithFreeSpaceUsingOldPage(Relation rel, BlockNumber oldPage,

+ Size spaceNeeded)

{

..

+ /*

+ * If fsm_set_and_search found a suitable new block, return that.

+ * Otherwise, search as usual.

+ */

..

}

In the above comment, you are referring wrong function.

2.

+static int

+fsm_search_from_addr(Relation rel, FSMAddress addr, uint8 minValue)

+{

+ Buffer buf;

+ int newslot = -1;

+

+ buf = fsm_readbuf(rel, addr, true);

+ LockBuffer(buf, BUFFER_LOCK_SHARE);

+

+ if (minValue != 0)

+ {

+ /* Search while we still hold the lock */

+ newslot = fsm_search_avail(buf, minValue,

+   addr.level == FSM_BOTTOM_LEVEL,

+   false);

In this new API, I don't understand why we need minValue != 0 check, basically if user of API doesn't want to search for space > 0, then what is the need of calling this API?  I think this API should use Assert for minValue!=0 unless you see reason for not doing so. 

>
> GetNearestPageWithFreeSpace? (although not sure that's accurate description, maybe Nearby would be better)
>

Better than what is used in patch.

Yet another possibility could be to call it as GetPageWithFreeSpaceExtended and call it from GetPageWithFreeSpace with value of oldPage as InvalidBlockNumber.