Aklakan commented on code in PR #2925: URL: https://github.com/apache/jena/pull/2925#discussion_r1916869473
########## jena-arq/src/main/java/org/apache/jena/sparql/engine/iterator/QueryIterLateral.java: ########## @@ -292,17 +295,33 @@ public Op transform(OpTable opTable) { // By the assignment restriction, the binding only needs to be added to each row of the table. Table table = opTable.getTable(); // Table vars. - List<Var> vars = new ArrayList<>(table.getVars()); - binding.vars().forEachRemaining(vars::add); - TableN table2 = new TableN(vars); + List<Var> tableVars = table.getVars(); + List<Var> vars = new ArrayList<>(tableVars); + + // Track variables that appear both in the table and the binding. + List<Var> commonVars = new ArrayList<>(); + + // Index variables in a set if there are more than a few of them. + Collection<Var> tableVarsIndex = tableVars.size() > 4 ? new HashSet<>(tableVars) : tableVars; + binding.vars().forEachRemaining(v -> { + if (tableVarsIndex.contains(v)) { + commonVars.add(v); + } else { + vars.add(v); + } + }); + + List<Binding> bindings = new ArrayList<>(table.size()); BindingBuilder builder = BindingFactory.builder(); table.iterator(null).forEachRemaining(row->{ - builder.reset(); - builder.addAll(row); - builder.addAll(binding); - table2.addBinding(builder.build()); + if (Algebra.compatible(row, binding, commonVars.iterator())) { Review Comment: There is potentially another can of worms I was about to open w.r.t. sep7: Perhaps its worthy of opening an issue and discussion on sparql-dev. The reason I added the compatibility check was because I had the following query in mind, which for reasons I do not yet understand is currently prohibited. Removing the restrictions in `SyntaxVarScope.checkLATERAL` on `Element_Data` (and `Element_Bind`) and adding the check for compatible bindings (effectively filtering bindings of tables down to those compatible with the current row; as done in the PR) naturally makes the query work. ```sparql SELECT * { VALUES ?department { <urn:dept1> <urn:dept2> } LATERAL { SELECT * { VALUES (?department ?employee) { ( <urn:dept1> <urn:person1> ) ( <urn:dept1> <urn:person2> ) ( <urn:dept2> <urn:person1> ) } } ORDER BY ?employee LIMIT 1 } } ``` | department | employee | |--------------------|---------| | <urn:dept1> | <urn:person1> | | <urn:dept2> | <urn:person1> | -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: pr-unsubscr...@jena.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: pr-unsubscr...@jena.apache.org For additional commands, e-mail: pr-h...@jena.apache.org