(Sorry, Daniel. Forgot to cc pgsql-hackers.) Hi, Daniel Thanks a lot for your response. As I can see for now, in my FYP, as the acyclic schema has the property that it has a join tree. I will check how many join trees it has and investigate any best option for the RSN schema. If it does have, I will modify the planner to just use this join tree if it detects a RSN database, then no need to use System R to search through all possible join trees. The implementation is narrow to only RSN schema. It might be too constraint for Postgres as a generic database system. For 'loose index join', I googled it and find the two sites useful to understand. http://dev.mysql.com/doc/refman/5.5/en/loose-index-scan.html http://wiki.postgresql.org/wiki/Loose_indexscan This is implemented in MySQL already, while Postgres only emulates the access method. Do you have any mail thread talking about the current design and progress? About the second topic, so currently TABLESAMPLE is not implemented inside Postgres? I didn't see this query before, but I googled it just now and the query seems very weird and interesting. http://www.fotia.co.uk/fotia/DY.18.TheTableSampleClause.aspx Still, do you have any mail thread talking about this? Thanks.
-- Best Regards Huang Qi Victor