On Sun, May 27, 2018 at 5:10 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Instrumenting the test case suggests that getQuadrant pretty much always > returns 1, resulting in a worst-case unbalanced SPGiST tree. I think this > is related to the fact that the test case inserts the values in increasing > order, so that new values are always greater than existing values in the > index.
I suspected the same. It reminded me of the weird behavior that the Postgres qsort() sometimes exhibits. > SPGiST is unable to rebalance its tree on the fly, so it's pretty > well screwed in this situation. It does finish eventually, but in about > 50x longer than GiST. I imagine the index's query performance would be > equally awful. Can you think of some way of side-stepping the issue? It's unfortunate that SP-GiST is potentially so sensitive to input order. -- Peter Geoghegan
