Hi Marc,

Thank you for your response.

If I understand correctly, with TinkerPop 3.5 I will be able to sort on property with missing values. It is a good news.

Do you know it JanusGraph 0.6.0 will be release with that version ?

Regarding the impact of the step order on index use, I wrote a strategy [1] that put HasStep and OrderStep before FilterStep if they follow a GraphStep.

Best regards,

Toom.

[1] https://gist.github.com/To-om/e7e406d85dcdd65bc2a533960b50a1d2

On Thursday, December 3, 2020 at 8:17:27 AM UTC+1 HadoopMarc wrote:

Hi Toom,

No solution, but the exception that you mention comes from TinkerPop:

https://github.com/apache/tinkerpop/blob/b4928e1262174a68c3dc1f3234d4340e266f8d98/docs/src/upgrade/release-3.5.x.asciidoc      (not released yet)

Apparently, you want all selected vertices, including the ones with null properties, so I would wait for TinkerPop 3.5 and in the mean time use your own workaround for a single filter criterion and do the ordering outside gremlin for more complex sets of filtering criteria.

Best wishes,      Marc

Op woensdag 2 december 2020 om 08:13:05 UTC+1 schreef t...@...:

Hello,

I'm using JanusGraph with Cassandra (0.5.2) and ElasticSearch.

I try to optimize my queries and use the mixed indexes as much as possible, in particular for sortings, but I have some difficulties:

It is not possible to sort by properties that can have missing values (or I get a "The property does not exist as the key has no associated value for the provided element"). Therefore I used ".order().by(coalesce(values('closingDate'), new Date()))" but in this case, the index is not used.

If there is only one sorting criterion, I probably can do something like:

g.inject(1).union(

  g.V().hasLabel('Case').has('closingDate').order().by('closingDate'),

  g.V().hasLabel('Case').hasNot('closingDate'))

But what is my best option if I want to use several criteria?

I also note that the FilterRankingStrategy strategy can have negative effect on performance when there are filters that don't use  index. For example, the following query is faster without step reordering.

g.V().hasLabel('Case').has('closingDate').order().by('closingDate').filter(out('attachment').has('file'))

FilterRanking swaps order() and filter() steps and then index is not used for sorting.

Any help will be much appreciated.

Toom.

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