Highlighting Error with `span_field_masking` Requires Indexing Offsets Unexpectedly #101804

ahoogol · 2023-11-04T10:30:09Z

Elasticsearch Version

8.10.4

Installed Plugins

No response

Java Version

bundled

OS Version

Elastic Cloud - GCP - Iowa (us-central1)

Problem Description

I encountered an issue when using the span_field_masking feature in Elasticsearch. When attempting to use the highlighter with this feature, the following error is thrown:

{
  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception",
        "reason": "field 'text' was indexed without offsets, cannot highlight"
      }
    ],
    "type": "search_phase_execution_exception",
    "reason": "all shards failed",
    "phase": "query",
    "grouped": true,
    "failed_shards": [
      {
        "shard": 0,
        "index": "test_mask",
        "node": "jUZ9p0ZtR6-xYevegW6O_Q",
        "reason": {
          "type": "illegal_argument_exception",
          "reason": "field 'text' was indexed without offsets, cannot highlight"
        }
      }
    ],
    "caused_by": {
      "type": "illegal_argument_exception",
      "reason": "field 'text' was indexed without offsets, cannot highlight",
      "caused_by": {
        "type": "illegal_argument_exception",
        "reason": "field 'text' was indexed without offsets, cannot highlight"
      }
    }
  },
  "status": 400
}

If I set "index_options": "offsets" in the mapping of the masked field 'stem', highlighting works as expected. However, I'm puzzled as to why the highlighter requires indexing offsets. I'd like to understand why the highlighter doesn't re-analyze the text to calculate offsets dynamically. My concern is that indexing offsets increases the index size, which I want to avoid.

Steps to Reproduce

PUT test_mask
{
  "mappings": {
    "properties": {
      "text": {
        "type": "text",
        "analyzer": "whitespace"
      },
      "stem": {
        "type": "text",
        "analyzer": "whitespace"
      }
    }
  }
}

PUT test_mask/_doc/1
{
  "text": "a _ a b",
  "stem": "_ b _ _"
}

GET test_mask/_search
{
  "query": {
    "span_near": {
      "clauses": [
        {
          "span_term": {
            "text": {
              "value": "a"
            }
          }
        },
        {
          "span_field_masking": {
            "field": "text", 
            "query": {
              "span_term": {
                "stem": {
                  "value": "b"
                }
              }
            }
          }
        }
      ],
      "slop": 0,
      "in_order": true
    }
  },
  "highlight": {
    "pre_tags": "(", 
    "post_tags": ")", 
    "fields": {
      "*": {}
    },
    "type": "unified"
  }
}

Expected result

I was expecting the highlight to look like this:

"highlight": {
  "text": [
    "(a) (_) a b"
  ]
}

The text was updated successfully, but these errors were encountered:

elasticsearchmachine · 2023-11-06T09:01:24Z

Pinging @elastic/es-search (Team:Search)

benwtrent · 2023-11-06T14:02:20Z

This is due to highlight.weight_matches_mode.enabled. I am not 100% sure why we are trying to get the offsets here.

But, to get around this bug,

PUT test_mask/_settings
{
  "index" : {
    "highlight.weight_matches_mode.enabled" : "false"
  }
}

Need to still dig into the correct fix here.

benwtrent · 2023-11-06T14:08:29Z

error-trace:

java.lang.IllegalArgumentException: field 'text' was indexed without offsets, cannot highlight
  at [email protected]/org.apache.lucene.search.uhighlight.FieldHighlighter.highlightOffsetsEnums(FieldHighlighter.java:157)
  at [email protected]/org.elasticsearch.lucene.search.uhighlight.CustomFieldHighlighter.highlightOffsetsEnums(CustomFieldHighlighter.java:106)
  at [email protected]/org.apache.lucene.search.uhighlight.FieldHighlighter.highlightFieldForDoc(FieldHighlighter.java:83)
  at [email protected]/org.elasticsearch.lucene.search.uhighlight.CustomFieldHighlighter.highlightFieldForDoc(CustomFieldHighlighter.java:63)
  at [email protected]/org.elasticsearch.lucene.search.uhighlight.CustomUnifiedHighlighter.highlightField(CustomUnifiedHighlighter.java:148)
  at [email protected]/org.elasticsearch.search.fetch.subphase.highlight.DefaultHighlighter.highlight(DefaultHighlighter.java:81)
  at [email protected]/org.elasticsearch.search.fetch.subphase.highlight.HighlightPhase$1.process(HighlightPhase.java:69)
  at [email protected]/org.elasticsearch.search.fetch.FetchPhase$1.nextDoc(FetchPhase.java:163)
  at [email protected]/org.elasticsearch.search.fetch.FetchPhaseDocsIterator.iterate(FetchPhaseDocsIterator.java:70)
  at [email protected]/org.elasticsearch.search.fetch.FetchPhase.buildSearchHits(FetchPhase.java:169)
  at [email protected]/org.elasticsearch.search.fetch.FetchPhase.execute(FetchPhase.java:78)
  at [email protected]/org.elasticsearch.search.SearchService.executeFetchPhase(SearchService.java:711)
  at [email protected]/org.elasticsearch.search.SearchService.executeQueryPhase(SearchService.java:682)
  at [email protected]/org.elasticsearch.search.SearchService.lambda$executeQueryPhase$2(SearchService.java:543)
  at [email protected]/org.elasticsearch.action.ActionRunnable$2.accept(ActionRunnable.java:51)
  at [email protected]/org.elasticsearch.action.ActionRunnable$2.accept(ActionRunnable.java:48)
  at [email protected]/org.elasticsearch.action.ActionRunnable$3.doRun(ActionRunnable.java:73)
  at [email protected]/org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26)
  at [email protected]/org.elasticsearch.common.util.concurrent.TimedRunnable.doRun(TimedRunnable.java:33)
  at [email protected]/org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingAbstractRunnable.doRun(ThreadContext.java:983)
  at [email protected]/org.elasticsearch.common.util.concurrent.AbstractRunnable.run(AbstractRunnable.java:26)
  at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
  at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
  at java.base/java.lang.Thread.run(Thread.java:1583)

ahoogol · 2023-11-07T07:22:00Z

This is due to highlight.weight_matches_mode.enabled. I am not 100% sure why we are trying to get the offsets here.

But, to get around this bug,
PUT test_mask/_settings
{
  "index" : {
    "highlight.weight_matches_mode.enabled" : "false"
  }
}
Need to still dig into the correct fix here.

@benwtrent Thank you for your suggestion. While running your suggested command, the error no longer occurs. However, I've noticed that the generated highlight doesn't match my expected output.

With your command:

"highlight": {
   "text": [
     "(a) _ (a) b"
   ],
   "stem": [
     "_ (b) _ _"
   ]
 }

I was expecting the highlight to look like this:

"highlight": {
  "text": [
    "(a) (_) a b"
  ]
}

Is there a way to achieve this expected result while avoiding the error?

benwtrent · 2023-11-07T13:02:46Z

@ahoogol turn on offsets for the fields and use "highlight.weight_matches_mode.enabled" : "true"

ahoogol · 2023-11-08T06:39:13Z

Thank you for your suggestion, @benwtrent. Yes, it highlights correctly when enabling offsets. But, my concern remains about the increase in index size. I'm still exploring alternative approaches to achieve the desired highlight without the need to turn on offsets to keep the index size manageable. If you have any further insights or suggestions, they would be greatly appreciated.

mayya-sharipova · 2023-12-14T20:43:38Z

@ahoogol If you use "require_field_match" : false as a highlighter option, you will get expected results without enabling offsets.

"highlight": {
    "require_field_match" : false,
    "pre_tags": "(", 
    "post_tags": ")", 
    "fields": {
      "*": {}
    },
    "type": "unified"
  }

Why it breaks is that internally we check that we the field we highlight on "text" is the same that the field that has matches "stem", but in this case there are different. That's the failure.

mayya-sharipova · 2023-12-14T20:46:10Z

I will add this to documentation for span_field_masking query and will close this issue.

Improvement includes: 1. Remove reference to Lucene queries (this information is not necessary for Elastic users, and can be outdated) 2. For `span_field_masking` include a node to use "require_field_match" : false parameter for highlighters to work. Closes elastic#101804

ahoogol · 2023-12-16T11:21:42Z

@mayya-sharipova I included "require_field_match": false in the highlighter options, but the resulting output remains different from what I expected:

Your suggestion output: (i tested it in 8.10.0 and 8.11.3)

"highlight": {
  "text": [
    "a _ (a) (b)"
  ]
}

Expected output:

"highlight": {
  "text": [
    "(a) (_) a b"
  ]
}

mayya-sharipova · 2023-12-19T19:19:33Z

@ahoogol Indeed you are right about the expected behaviour, but it is not supported on span_field_masking query. And it would be not easy to support it (without indexing with offsets).

The highlighting behaviour that you expect is based on Matches and was added from 8.10. But it relies on the fact that the highlighted field contains query terms, which is not your case.

I have added a documentation clarifying that span_field_masking query has unexpected highlighting behaviour and should be used with require_field_match = false.

I also modified the type of this issue as a "feature", that we may tackle sometime in the future.

Improvement includes: 1. Remove reference to Lucene queries (this information is not necessary for Elastic users, and can be outdated) 2. For `span_field_masking` include a node to use "require_field_match" : false parameter for highlighters to work. Closes #101804

Improvement includes: 1. Remove reference to Lucene queries (this information is not necessary for Elastic users, and can be outdated) 2. For `span_field_masking` include a node to use "require_field_match" : false parameter for highlighters to work. Closes elastic#101804

elasticsearchmachine · 2024-07-12T09:33:25Z

Pinging @elastic/es-search-relevance (Team:Search Relevance)

ahoogol added >bug needs:triage Requires assignment of a team area label labels Nov 4, 2023

ahoogol changed the title ~~Unexpected Need to index offsets when using span_field_masking~~ Highlighting Error with span_field_masking Requires Indexing Offsets Unexpectedly Nov 4, 2023

pxsalehi added :Search Relevance/Highlighting How a query matched a document and removed needs:triage Requires assignment of a team area label labels Nov 6, 2023

elasticsearchmachine added the Team:Search Meta label for search team label Nov 6, 2023

mayya-sharipova mentioned this issue Dec 15, 2023

Improve span queries documentation #103490

Merged

mayya-sharipova self-assigned this Dec 18, 2023

mayya-sharipova added >feature and removed >bug labels Dec 19, 2023

mayya-sharipova closed this as completed in #103490 Dec 19, 2023

mayya-sharipova reopened this Dec 19, 2023

mayya-sharipova removed their assignment Dec 20, 2023

javanna added >enhancement and removed >feature labels Jun 25, 2024

javanna added Team:Search Relevance Meta label for the Search Relevance team in Elasticsearch and removed Team:Search Meta label for search team labels Jul 12, 2024

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Highlighting Error with `span_field_masking` Requires Indexing Offsets Unexpectedly #101804

Highlighting Error with `span_field_masking` Requires Indexing Offsets Unexpectedly #101804

ahoogol commented Nov 4, 2023 •

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elasticsearchmachine commented Nov 6, 2023

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elasticsearchmachine commented Jul 12, 2024

Highlighting Error with span_field_masking Requires Indexing Offsets Unexpectedly #101804

Highlighting Error with span_field_masking Requires Indexing Offsets Unexpectedly #101804

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ahoogol commented Nov 4, 2023 • edited Loading

Elasticsearch Version

Installed Plugins

Java Version

OS Version

Problem Description

Steps to Reproduce

Expected result

elasticsearchmachine commented Nov 6, 2023

benwtrent commented Nov 6, 2023

benwtrent commented Nov 6, 2023

ahoogol commented Nov 7, 2023 • edited Loading

benwtrent commented Nov 7, 2023

ahoogol commented Nov 8, 2023

mayya-sharipova commented Dec 14, 2023 • edited Loading

mayya-sharipova commented Dec 14, 2023

ahoogol commented Dec 16, 2023 • edited Loading

mayya-sharipova commented Dec 19, 2023 • edited Loading

elasticsearchmachine commented Jul 12, 2024

Highlighting Error with `span_field_masking` Requires Indexing Offsets Unexpectedly #101804

Highlighting Error with `span_field_masking` Requires Indexing Offsets Unexpectedly #101804

ahoogol commented Nov 4, 2023 •

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ahoogol commented Nov 7, 2023 •

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mayya-sharipova commented Dec 14, 2023 •

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ahoogol commented Dec 16, 2023 •

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mayya-sharipova commented Dec 19, 2023 •

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