Thanks, Konstantin. I have logged https://issues.apache.org/jira/browse/CALCITE-4597 to make the policy configurable. Eventually I would like to allow empty row types throughout the system, but until then, rules and RelFieldTrimmer should follow Postel’s law [1] and accept empty row types but try not to produce them.
Julian [1] https://en.wikipedia.org/wiki/Robustness_principle > On May 5, 2021, at 12:51 AM, Konstantin Orlov <kor...@gridgain.com> wrote: > >> Konstantin, can you log it, please > > Yes, sure. Here it is [1] > > [1] https://issues.apache.org/jira/browse/CALCITE-4596 > <https://issues.apache.org/jira/browse/CALCITE-4596> > > -- > Regards, > Konstantin Orlov > > > >> On 4 May 2021, at 21:29, Julian Hyde <jh...@apache.org> wrote: >> >> Regardless of which direction we go (allowing zero-field record types, or >> disallowing them), Konstantin has found a bug. Konstantin, can you log it, >> please. >> >> On 2021/04/29 14:25:27, Konstantin Orlov <kor...@gridgain.com> wrote: >>> Hi all. >>> >>> I faced a problem preventing certain queries being planned because >>> RelFieldTrimmer throws >>> an ArrayIndexOutOfBoundsException with message "Index -1 out of bounds for >>> length 0”. >>> >>> The problem is here [1]: >>> >>> // If they are asking for no fields, we can't give them what they want, >>> // because zero-column records are illegal. Give them the last field, >>> // which is unlikely to be a system field. >>> if (fieldsUsed.isEmpty()) { >>> fieldsUsed = ImmutableBitSet.range(fieldCount - 1, fieldCount); >>> } >>> >>> In case fieldsUsed.isEmpty we returns last field, but it is currently >>> possible that fieldCount=0 as well. >>> >>> After some investigation I find out that the reason is empty record derived >>> as row type for Aggregate. >>> It is possible when an aggregate has an empty group key and no aggregate >>> calls. >>> >>> So the question is whether an empty record is a legal row type for an >>> aggregation node? >>> >>> Below is a reproducer for this problem, just put it at RelFieldTrimmerTest: >>> >>> @Test void test() { >>> class ContextImpl implements Context { >>> final Object target; >>> >>> ContextImpl(Object target) { >>> this.target = Objects.requireNonNull(target, "target"); >>> } >>> >>> @Override public <T extends Object> @Nullable T unwrap(Class<T> clazz) { >>> if (clazz.isInstance(target)) { >>> return clazz.cast(target); >>> } >>> return null; >>> } >>> } >>> >>> // RelBuilder hides problem when simplifyValues=true, hence we need to >>> disable it >>> final RelBuilder builder = RelBuilder.create(config() >>> .context(new >>> ContextImpl(RelBuilder.Config.DEFAULT.withSimplifyValues(false))).build()); >>> >>> final RelNode root = >>> builder.scan("EMP") >>> .aggregate(builder.groupKey()) >>> .filter(builder.literal(false)) >>> .project(builder.literal(42)) >>> .build(); >>> >>> final RelFieldTrimmer fieldTrimmer = new RelFieldTrimmer(null, builder); >>> fieldTrimmer.trim(root); // fails with ArrayIndexOutOfBoundsException: >>> Index -1 out of bounds for length 0 >>> } >>> >>> >>> [1] >>> https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/sql2rel/RelFieldTrimmer.java#L1197 >>> >>> -- >>> Regards, >>> Konstantin Orlov >>> >>> >>> >>> >>> >
