??>> I'm surprised you are seeing this difference on Postmodern, unless ??>> your input name is matching a large number of objects (i.e. s is ??>> large). I had thought that the native PostgreSQL backend, ??>> postmodern, ??>> fixed the linear cost problem of CL-SQL indices and provides the ??>> same ??>> O(s) performance that BDB does, but I'm not certain (Henrik? ??>> Robert?). It sounds like you are seeing a high linear cost.
RLR> Postmodern does exactly the same thing that CL-SQL does in this RLR> respect; the code was copied directly from the CL-SQL code. from original Henrik's announcement: ---- The implementation is actually quite different from the clsql backend. ... The db-postmodern cursor is based on a sql cursor. Each btree has its own database table. ---- IE> SQL backend cannot support the ordering constraints of an index IE> without reading all the objects into memory and postmodern cannot support them too. however we do not really need to support ordering to do by-value queries. as for by-range queries, they should work in db-postmodern when keys are strings-only or integers-only, which is probably most useful case. we are going to improve it to support NILs among values. by the way, "ugly fix" Henrik mentions in original post is blocking range queries. for now we cannot even do even by-value queries because of "special way" map-index works, so "ugly fix" is needed. but we are going to provide optimized specialization for doing by-value queries, and fix stuff so by-range queries will work at least in some limited way. also in process of improving cursor implementation we are going to provide optional "compatible" mode that will allow degrading to CLSQL backend style (fetch everything and sort on Lisp side), so people who want to do funky range queries will be able to do so, but they will loose ability to work with arbitrarily large tables. it might be possible to implement lisp-compare in postgres somehow, but IMHO it doesn't worth effort to do so -- range queries make sense when you know type of data. _______________________________________________ elephant-devel site list elephant-devel@common-lisp.net http://common-lisp.net/mailman/listinfo/elephant-devel
