Hi, The following documentation page explains the GiST API to extensions authors: http://www.postgresql.org/docs/current/static/gist-implementation.htm
I think we should be a little more verbose, and at least explains some more the big picture: same/consistent/union are responsible for correctness of the index while penalty and picksplit are responsible for performances of it, which leaves compress/decompress, to use when leaf/nodes are not the same datatype. This leaf/node construct is explained in the last paragraph of following page, but can exists directly into the C module too: http://www.postgresql.org/docs/current/static/xindex.html The consistent and union should get a lot of attention, and when exactly do your operators need RECHECK is still unclear to me. It's hard to give precise advices about consistent/union in a generic way, but I've been given the following general rule (thanks RhodiumToad): (z is consistent with x) implies (z is consistent with union(x,y)) What's unclear too is memory management: when to palloc() and when to reuse arguments given by -core GiST support functions. I know it was a game of trial and error to get it right, and while I know it's working now, I'd be in a bad position to explain how and why. Maybe reading the source code is what to do here, but a detailed API expectancies page in the documentation wouldn't hurt... Regards, -- dim I didn't propose a real doc patch mainly because english isn't my native language, and while you'll have to reword the content...
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