04.01.2022 22:19, Tom Lane wrote: > Alexander Lakhin <exclus...@gmail.com> writes: >> While testing the index-only scan fix, I've discovered that replacing >> the index-only scan with the index scan changes contrib/btree_gist >> output because index-only scan for btree_gist returns a string without >> padding. > Ugh, yeah. This seems to be because gbt_bpchar_compress() strips > trailing spaces (using rtrim1) before storing the value. The > idea evidently is to simplify gbt_bpchar_consistent, but it's not > acceptable if the opclass is supposed to support index-only scan. > > I see two ways to fix this: > > * Disallow index-only scan, by removing the fetch function for this > opclass. This'd require a module version bump, so people wouldn't > get that fix automatically. > > * Change gbt_bpchar_compress to not trim spaces (it becomes just > like gbt_text_compress), and adapt gbt_bpchar_consistent to cope. > This does nothing for the problem immediately, unless you REINDEX > affected indexes --- but over time an index's entries would get > replaced with untrimmed versions. I think that the second way is preferable in the long run. It doesn't need an explanation after years, why index-only scan is not supported for that type. One-time mentioning the change and the need for REINDEX in release notes seems more future-oriented to me.
Best regards, Alexander
