Hi Laurenz, > > In your approach 1 to 3, what do you mean with "load into main memory"?
I forgot to say: I use Java and connect with JDBC. in approach 1 I do an initial loading of the entire relation, by executing 1 SQL query to load all edges in main memory, where I create my main memory structure as an adjacency list. > Do you > a) make sure that the data you talk about are in the PostgreSQL buffer > cache > or > b) retrieve the data from PostgreSQL and store it somewhere in your > application? In approach 1 I do that, as described before. But after each experiment I restart a new java process. > > To clear PostgreSQL's cache, restart the server. > That should be a fast operation. > Since version 8.3, PostgreSQL is smart enough not to evict the > whole cache for a large sequential scan. > > To flush the filesystem cache (from Linux 2.6.16 on), use > sync; echo 3 > /proc/sys/vm/drop_caches I started to do that , and yes, this solves my problem!! I assume that deleting file system cache implies that also postgres cache is deleted, isn't it ? so i will invoke after each experiment this command thanks a lot!! Markus
