[CALCITE-4327] RelBuilder#scan(...) should work when used in RelRule#onMatch as call.builder()

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.26.0
• Component/s: core
• Assignee: Unassigned
• Reporter: Vladimir Sitnikov
• Created: 11/Oct/20 13:15
• Updated: 11/Oct/20 22:53

Description

It turns out RelBuilder#relOptSchema is often null.
For instance,

public abstract class RelOptRuleCall {
  public RelBuilder builder() {
    return rule.relBuilderFactory.create(rel(0).getCluster(), /* schema= */ null);
  }

It leads to NPE in user code.
I suggest either populate relOptSchema with root schema by default or remove the field to avoid confusion for those who would try scan(...) method.

It might make sense to add RelOptSchema parameter to scan(Iterable<String>) method as well.

Sample use case:

    @Override
    public void onMatch(RelOptRuleCall call) {
        List<String> indexName = ...;
        RelBuilder relBuilder = call.builder()
                .scan(indexName);

Caused by: java.lang.NullPointerException
	at org.apache.calcite.tools.RelBuilder.scan(RelBuilder.java:1094)
	at com.github.vlsi.mat.calcite.schema.objects.InstanceAccessByClassIdRule.onMatch(InstanceAccessByClassIdRule.java:44)
	at org.apache.calcite.plan.volcano.VolcanoRuleCall.onMatch(VolcanoRuleCall.java:229)
	... 75 more