I was doing concurrent inserts (just running monetdb_query('INSERT INTO ...'); in a loop) with 2 workers. After ~172,000 inserts on the first worker I got this message: Error: SQLException:optimizer: 'deadcode' should be used at least once !SQLException:optimizer: pipeline set to 'inline,remap,evaluate,costModel,coercions,emptySet,aliases,mergetable,deadcode,constants,commonTerms,joinPath,deadcode,reduce,garbageCollector,dataflow,history,multiplex' And at the same time on the second worker I got: Error: SQLException:optimizer: 'multiplex' should be the last !SQLException:optimizer: 'deadcode' should be used at least once !SQLException:optimizer: pipeline set to 'inline,remap,evaluate,costModel,coercions,emptySet,aliases,mergetable,deadcode,constants,commonTerms,joinPath,deadcode,reduce,garbageCollector,dataflow,history,multiplex' Does anyone know what this might mean? At first I thought I may have made too big of a transaction but it seems monetdb runs in autocommit mode by default. Thanks, Guillaume