[jira] [Created] (CALCITE-4995) ArrayIndexOutOfBoundsException caused by RelFieldTrimmer on SEMI/ANTI join

["Ruben Q L (Jira)" <ji...@apache.org>]

Ruben Q L created CALCITE-4995:
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             Summary: ArrayIndexOutOfBoundsException caused by RelFieldTrimmer on SEMI/ANTI join
                 Key: CALCITE-4995
                 URL: https://issues.apache.org/jira/browse/CALCITE-4995
             Project: Calcite
          Issue Type: Bug
          Components: core
    Affects Versions: 1.29.0
            Reporter: Ruben Q L
            Assignee: Ruben Q L


(Unit test to be provided)

It seems {{RelFieldTrimmer}} can cause an {{ArrayIndexOutOfBoundsException}} on certain plans involving SEMI/ANTI join (i.e. joins that do NOT project the RHS fields).
The root cause seems to be the "early return" in {{RelFieldTrimmer#trimFields(Join join, ImmutableBitSet fieldsUsed, Set<RelDataTypeField> extraFields)}} when nothing has been trimmed inside join's inputs (so the join itself can be return as it is):
{code:java}
    if (changeCount == 0
        && mapping.isIdentity()) {
      return result(join, Mappings.createIdentity(fieldCount));
    }
{code}
The problem is that this {{fieldCount}} is an addition of LHS + RHS fields (+ system fields); but in case of a SEMI/ANTI the mappings to be returned must not consider RHS fields (since they are not projected by these join types).

The problem only happens here (when the trimmer does not trim the join). Notice that, a few lines below, in the "other return scenario" of the method (when something has been trimmed), there is a special treatment of the mapping for ANTI/SEMI, so things will work fine in this case:
{code:java}
    switch (join.getJoinType()) {
    case SEMI:
    case ANTI:
      // For SemiJoins and AntiJoins only map fields from the left-side
      if (join.getJoinType() == JoinRelType.SEMI) {
        relBuilder.semiJoin(newConditionExpr);
      } else {
        relBuilder.antiJoin(newConditionExpr);
      }
      Mapping inputMapping = inputMappings.get(0);
      mapping = Mappings.create(MappingType.INVERSE_SURJECTION,
          join.getRowType().getFieldCount(),
          newSystemFieldCount + inputMapping.getTargetCount());
      for (int i = 0; i < newSystemFieldCount; ++i) {
        mapping.set(i, i);
      }
      offset = systemFieldCount;
      newOffset = newSystemFieldCount;
      for (IntPair pair : inputMapping) {
        mapping.set(pair.source + offset, pair.target + newOffset);
      }
      break;
    default:
      relBuilder.join(join.getJoinType(), newConditionExpr);
    }
    relBuilder.hints(join.getHints());
    return result(relBuilder.build(), mapping);
{code}



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