Thank you for the information. Tomorrow, I will also run a few tests to measure the time required to collect tids from the index; however, since I do not work with vanilla postgres, the results may vary.
If the results indicate that this procedure is time-consuming, I maybe will develop an additional patch specifically for b-tree indexes, as they are the default and most commonly used type.
> I think it's to avoid duplicate errors when adding tuples from STIP to the main index, > but couldn't we just suppress that error during validation and skip the new tuple insertion if it already exists?
In some cases, it is not possible: – Some index types (GiST, GIN, BRIN) do not provide an easy way to detect such duplicates. – When we are building a unique index, we cannot simply skip duplicates, because doing so would also skip the rows that should prevent the unique index from being created (unless we add extra logic for B-tree indexes to compare TIDs as well).
> The main index may get huge after building, and iterating over it in a single thread and then sorting tids can be time consuming. My tests indicate that the overhead is minor compared with the time spent scanning the heap and building the index itself.
> At least I guess one can skip it when STIP is empty. Yes, that’s a good idea; I’ll add it later.
> p.s. I noticed that `stip.c` has a lot of functions that don't follow the Postgres coding style of return type on separate line. Hmm... I’ll fix that as well.
