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https://issues.apache.org/jira/browse/SOLR-5354?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13833312#comment-13833312
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Hoss Man commented on SOLR-5354:
--------------------------------
Steve: looks great for the most part.
a few comments / questions...
* call me paranoid, but i really dislike distrib tests that *only* use the
query() method to ensure that the distrib response is the same as the control
response -- could we please add some assertions that use queryServer() to prove
the docs are coming back in the right order in the distrib test?
* the test should really sanity check that multi-level sorts (eg: "payload asc,
id desc") are working properly
* we should be really clear & careful in the javadocs for
FieldType.marshalSortValue and FieldType.unmarshalSortValue -- in your patch
they refer to "a value of this FieldType" but that's not actually what they
operate on. They operate on the values used by the FieldComparator returned by
the SortField for this FieldType (ie: SortableDoubleField's toObject returns a
Double, but the marshal method operates on ByteRef)
* I'm confused why we still need comparatorNatural() and it's use for
REWRITEABLE. Why not actually rewrite() the SortField using the local
IndexSearcher and then wrap the rewritten SortField's FieldComparator using
comparatorFieldComparator() just like any other SortField? Since we're only
ever going to compare the raw values on the coordinator it shouldn't matter if
we rewrite in terms of the local IndexSearcher - it's the best we can do, and
that seems safer then assuming REWRITABLE == function and trusting
comparatorNatural. (ie: consider someone who writes a custom FieldType that
uses REWRITABLE)
* don't the marshal methods in StrField, TextField, and CollationField need
null checks (for the possibilities of docs w/o a value in the sort field?)
* do we even have any existing tests of distributed sorting on strings &
numerics using sortMisstingLast / sortMissingFirst to be sure we don't break
that?
> Distributed sort is broken with CUSTOM FieldType
> ------------------------------------------------
>
> Key: SOLR-5354
> URL: https://issues.apache.org/jira/browse/SOLR-5354
> Project: Solr
> Issue Type: Bug
> Components: SearchComponents - other
> Affects Versions: 4.4, 4.5, 5.0
> Reporter: Jessica Cheng
> Assignee: Steve Rowe
> Labels: custom, query, sort
> Attachments: SOLR-5354.patch, SOLR-5354.patch
>
>
> We added a custom field type to allow an indexed binary field type that
> supports search (exact match), prefix search, and sort as unsigned bytes
> lexicographical compare. For sort, BytesRef's UTF8SortedAsUnicodeComparator
> accomplishes what we want, and even though the name of the comparator
> mentions UTF8, it doesn't actually assume so and just does byte-level
> operation, so it's good. However, when we do this across different nodes, we
> run into an issue where in QueryComponent.doFieldSortValues:
> // Must do the same conversion when sorting by a
> // String field in Lucene, which returns the terms
> // data as BytesRef:
> if (val instanceof BytesRef) {
> UnicodeUtil.UTF8toUTF16((BytesRef)val, spare);
> field.setStringValue(spare.toString());
> val = ft.toObject(field);
> }
> UnicodeUtil.UTF8toUTF16 is called on our byte array,which isn't actually
> UTF8. I did a hack where I specified our own field comparator to be
> ByteBuffer based to get around that instanceof check, but then the field
> value gets transformed into BYTEARR in JavaBinCodec, and when it's
> unmarshalled, it gets turned into byte[]. Then, in QueryComponent.mergeIds, a
> ShardFieldSortedHitQueue is constructed with ShardDoc.getCachedComparator,
> which decides to give me comparatorNatural in the else of the TODO for
> CUSTOM, which barfs because byte[] are not Comparable...
> From Chris Hostetter:
> I'm not very familiar with the distributed sorting code, but based on your
> comments, and a quick skim of the functions you pointed to, it definitely
> seems like there are two problems here for people trying to implement
> custom sorting in custom FieldTypes...
> 1) QueryComponent.doFieldSortValues - this definitely seems like it should
> be based on the FieldType, not an "instanceof BytesRef" check (oddly: the
> comment event suggestsion that it should be using the FieldType's
> indexedToReadable() method -- but it doesn't do that. If it did, then
> this part of hte logic should work for you as long as your custom
> FieldType implemented indexedToReadable in a sane way.
> 2) QueryComponent.mergeIds - that TODO definitely looks like a gap that
> needs filled. I'm guessing the sanest thing to do in the CUSTOM case
> would be to ask the FieldComparatorSource (which should be coming from the
> SortField that the custom FieldType produced) to create a FieldComparator
> (via newComparator - the numHits & sortPos could be anything) and then
> wrap that up in a Comparator facade that delegates to
> FieldComparator.compareValues
> That way a custom FieldType could be in complete control of the sort
> comparisons (even when merging ids).
> ...But as i said: i may be missing something, i'm not super familia with
> that code. Please try it out and let us know if thta works -- either way
> please open a Jira pointing out the problems trying to implement
> distributed sorting in a custom FieldType.
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