Gin index support in hypopg

[SrividyaReddy296]

Hi! Are there any plans for GIN indices in hypopg? How difficult that would be to implement?
Thank you!!

[rjuju]

Hi,

I think this has been asked before and I thought it was documented but unfortunately not. Almost all the code is already compatible with GIN (and GiST or other unsupported index methods), the main problem is the size estimation. For btree and other "regular" index methods, it's somewhat easy to get a gross estimate of the number of rows and pages of an index based on the table statistics.

But for GIN and the other unsupported methods it's much more complicated, as it will wildly depends on the operator class used and the data itself. I think that the only way to get a reasonable approximation would be to implement some kind of "hypothetical analyze", to fetch a subset of the table, extract the data and see what you would get out of the operator class functions. But that's a very big project that hasn't been done yet.

If someone has a better idea on how to estimate a GIN (GiST...) index that would be very useful.