Hi, I’m facing a strange issue with Flink 1.8.1. I’ve implemented a StreamTableSource that implements FilterableTableSource and ProjectableTableSource. However, I’m seeing that during the logical plan optimization (TableEnvironment.scala:288), the applyPredicates method is called but the resulting plan does NOT contain the source with the filter pushed.
It appears that the problem is in the VolcanoPlanner.findBestExp method; when it reaches “root.buildCheapestPlan”, the resulting RelNode does not contain the filtered source. Additionally, I added a breakpoint in FlinkLogicalTableSourceScan#computeSelfCost, and the tableSource never has the predicates pushed. I verified that in the PushFilterIntoTableSourceScanRule, the resulting source always has the predicates pushed. Amusingly, this issue causes queries like “SELECT a FROM src WHERE a = 123” to be rewritten to “SELECT 123 FROM src” :-) Does anyone have any advice on debugging/working around this without disabling predicate pushdown on the source?
