It’s a bit unusual that you are converting physical algebra (enumerable) to SQL.
EnumerableLimit only exists in physical algebra. In logical algebra, there is Sort, which includes an optional limit and offset. So, you could perhaps convert EnumerableLimit to Sort before calling RelToSqlConverter. Or add a handler to RelToSqlConverter that does this internally. In any case, please log a JIRA case. Contributions welcome. Julian > On Mar 11, 2019, at 1:20 PM, Anupam Aggarwal <[email protected]> > wrote: > > Hi, > > We are using calcite to do MV rewrite, for we convert the original sql to > a relNode, optimize the relNode and reconvert it back to Sql (using > RelToSqlConverter) > > Currently a query like this > > *Select * from foo.bar where limit 10 ; * > > Results in the following plan (after a MV rewrite to a different table) > > EnumerableLimit(fetch=[1]): rowcount = 1.0, cumulative cost = {1.0 rows, > 2.0 cpu, 0.0 io}, id = 303 > EnumerableTableScan(table=[[viewSchema, barView]]): rowcount = 1.0, > cumulative cost = {0.0 rows, 1.0 cpu, 0.0 io}, id = 176 > > While converting the relNode to sql using RelToSqlConverter we get an > exception saying > Caused by: java.lang.reflect.InvocationTargetException > Caused by: java.lang.AssertionError: Need to implement > org.apache.calcite.adapter.enumerable.EnumerableLimit > > Seems like RelToSqlConverter does not handle EnumerableLimit , Is this a bug ? > The fix is adding a visit method to RelToSqlConverter with > EnumerableLimit as the function argument. > > > public Result visit(EnumerableLimit e) { > Result x = visitChild(0, e.getInput()); > Builder builder = x.builder(e, Clause.FETCH); > > if (e.fetch != null) { > builder = x.builder(e, Clause.FETCH); > builder.setFetch(builder.context.toSql(null, e.fetch)); > x = builder.result(); > } > if (e.offset != null) { > builder = x.builder(e, Clause.OFFSET); > builder.setOffset(builder.context.toSql(null, e.offset)); > x = builder.result(); > } > return x; > } > > Found some relevant discussion here - > https://jira.apache.org/jira/browse/CALCITE-1003. > Can you please help in understanding if this handling is correct? (or > if there is a better way ) > > Thanks > Anupam
