Aklakan commented on code in PR #2925:
URL: https://github.com/apache/jena/pull/2925#discussion_r1916869473
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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:
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 (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> |
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