Aklakan commented on code in PR #2925:
URL: https://github.com/apache/jena/pull/2925#discussion_r1918597769
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jena-arq/src/main/java/org/apache/jena/sparql/engine/iterator/QueryIterLateral.java:
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@@ -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:
> In general, some system have optimizations that on the static analysis of
the query.
Well, the tradeoff to what extend existing implementations need to drive
restrictions of new features in a standard.
For the sake of closing the issue, should I modify/simplify the logic in
QueryIterLateral or should I leave the slightly more general approach as it is
for now? ~Essentially, the var scope check should prevent non-empty sets of
commonVars.~ No, commonVars is non-empty in the case of nested laterals. I need
to check what change would be necessary.
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