Hi Gregory, thank you very much for you answer!
> > > what is the default implementation for GiST index? B-Tree or R-Tree? > > That is, if i execute the following SQL command: > > > > CREATE index ON table USING Gist (column) > > > > what is the type of the index that is actually built? > > uhm, GIST. GIST is a particular type of index just like btree. according to the documentation (ch 11.2) "GiST indexes are not a single kind of index, but rather an infrastructure within wich many different indexing strategies can be implemented", and (ch 50.1) "B-Tree, R-Tree and many other indexing schemes can be implemented in GiST". Moreover, according to what i found on the web (see http://www.sai.msu.su/~megera/postgres/gist/ ) some of such implementations are now included in the core of Postgres. I supposed there was a way to specify one among the implementation provided. What are you actually trying to do? Do you have a particular problem you're > trying to solve? I wanted to test the suitability and the efficiency of R-Tree/GiST for query involving standard PostgreSQL temporal column data. > How can I specify in SQL one of the two implementations provided (e.g. > > R-Tree)? > > R-Tree indexes don't exist in Postgres any more. GIST indexes are very > similar > only more general. They handle 2D geometric data types like RTree did > previously as well as n-dimensional data types and other more exotic > things > like intarrays and full text search. Are these functionalities all included by default in the standard GiST indexing? There are different "kinds" of GIST indexes which you can specify by > specifying an operator class with you define the index. But most data types > only have a single operator class available to them so that's probably not > what you need unless you're trying to do something unusual. An "operator class" defines a set of operators which can be optimized by an > index organized the same way and usually correspond to a particular > interpretation of the data type. Is the specification of the operator class done when I create the index? Or is the suitable operator class automatically loaded according to the data type of the column on which I build the index? And if I would specify a different operator class, how can i do it? May I provide a different operator class beyond the ones provided? Thank you very much. Regards, -Elena
