I have followed the instructions below to no avail .... any thoughts? http://jdbc.postgresql.org/documentation/83/query.html#query-with-cursor
This is what happens when I reduce the fetch_size to 50 ... stops after about 950msec and 120 fetches (6k rows) .... 13:59:56,054 [PerfDataMigrator] ERROR com.hyper9.storage.sample.persistence.PersistenceManager:3216 - Unexpected error while migrating sample data: 6000 org.postgresql.util.PSQLException: ERROR: portal "C_14" does not exist at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1592) at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1327) at org.postgresql.core.v3.QueryExecutorImpl.fetch(QueryExecutorImpl.java:1527) at org.postgresql.jdbc2.AbstractJdbc2ResultSet.next(AbstractJdbc2ResultSet.java:1843) at org.apache.commons.dbcp.DelegatingResultSet.next(DelegatingResultSet.java:169) at org.apache.commons.dbcp.DelegatingResultSet.next(DelegatingResultSet.java:169) at com.hyper9.storage.sample.persistence.PersistenceManager$Migrator.run(PersistenceManager.java:3156) at java.lang.Thread.run(Thread.java:619) Cheers Dave On Thu, Apr 15, 2010 at 2:42 PM, Dave Crooke <dcro...@gmail.com> wrote: > Hey folks > > I am trying to do a full table scan on a large table from Java, using a > straightforward "select * from foo". I've run into these problems: > > 1. By default, the PG JDBC driver attempts to suck the entire result set > into RAM, resulting in *java.lang.OutOfMemoryError* ... this is not cool, > in fact I consider it a serious bug (even MySQL gets this right ;-) I am > only testing with a 9GB result set, but production needs to scale to 200GB > or more, so throwing hardware at is is not feasible. > > 2. I tried using the official taming method, namely * > java.sql.Statement.setFetchSize(1000)* and this makes it blow up entirely > with an error I have no context for, as follows (the number C_10 varies, > e.g. C_12 last time) ... > > org.postgresql.util.PSQLException: ERROR: portal "C_10" does not exist > at > org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:1592) > at > org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:1327) > at > org.postgresql.core.v3.QueryExecutorImpl.fetch(QueryExecutorImpl.java:1527) > at > org.postgresql.jdbc2.AbstractJdbc2ResultSet.next(AbstractJdbc2ResultSet.java:1843) > > This is definitely a bug :-) > > > Is there a known workaround for this ... will updating to a newer version > of the driver fix this? > > Is there a magic incation of JDBC calls that will tame it? > > Can I cast the objects to PG specific types and access a hidden API to turn > off this behaviour? > > If the only workaround is to explicitly create a cursor in PG, is there a > good example of how to do this from Java? > > Cheers > Dave > > > > > >