Hi, I'm completely new to monetdb and have been dropped in at the deep end with an application support issue at a customer site. The release running is FEB2013 SP6 on Windows Server 2012 64 bit. There are customizations including aggregate functions written in MAL so the issue may not derive from monetdb source. I have searched bug lists but not found an obvious match for the error that is being reported, so I'm wondering whether anyone has experienced similar symptoms and found a solution. (Bug 3375 is the closest match and was fixed in the release in use) The reported problem is that the application works normally for a period until something causes monetdb to consistently report errors: Error: GDK reported error. SQLState: 22000 ErrorCode: 0 Error: BATfetchjoin(tmp_3662,tmp_4362) does not hit always (|bn|=0 != 2660745=|l|) => can't use fetchjoin. SQLState: 22000 ErrorCode: 0 It has been noted that the error appears to be in response to some SQL which up to that point had been working : select count(*) as "_m1_", avg("B"."C") as "_m2_" from "A" left outer join "B" on "A"."A_ID" = "B"."A_ID" Further, there is a foreign key relationship defined: ALTER TABLE "B" ADD CONSTRAINT fk_B FOREIGN KEY ("A_ID") REFERENCES "A"("A_ID") and dropping the index corresponding to the foreign key causes monetdb to recover. i.e. drop index fk_B All suggestions would be gratefully appreciated. In the meantime, I will try to reproduce the issue in house. Thanks, John Burgess ________________________________