Re: "Write amplification" is made worse by "getting tired" while inserting into nbtree secondary indexes (Was: Why B-Tree suffix truncation matters)

Peter Geoghegan <pg(at)bowt(dot)ie> writes:
> I've done plenty of research into the history of this hack. It was
> your work, but it does actually make sense in the context of today's
> nbtree code. It is essential with scankey-wise duplicates, since
> groveling through hundreds or even thousands of pages full of
> duplicates to find free space (and avoid a page split) is going to
> have a very serious downside for latency.

Well, the actual problem was O(N^2) behavior:

https://www.postgresql.org/message-id/2378.967216388%40sss.pgh.pa.us

https://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=40549e9cb5abd2986603883e4ab567dab34723c6

I certainly have no objection to improving matters, but let's be sure
we don't re-introduce any two-decade-old problems.

regards, tom lane