Error when doing a prefix search when the prefix is min_chars -1

[joancf]

Elasticsearch Version

8.6.2

Installed Plugins

elastiknn-8.6.2.1.zip

Java Version

openjdk 18.0.2.1 2022-08-18

OS Version

docker: Linux c30f7a57fb60 5.4.0-139-generic #156-Ubuntu SMP Fri Jan 20 17:27:18 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

Problem Description

When doing a prefix search over a text field with index_prefixes and min_chars = X , if the length of the prefix is X-1, the search fails with a lucene null pointer error:

this error has been reported (and solved) for openserarch, here opensearch-project/OpenSearch#2826

Steps to Reproduce

1 crate an index with index prefix and index some docs:

PUT test_prefix
{
  "mappings": {
    "properties": {
      "t": {
        "type": "text",
        "index_prefixes": {"min_chars":3}
      }
    }
  }
}

POST test_prefix/_doc
{
  "t":"This is the test to these kind of errors"
}

Do the search , the first and second work correctly while the last one, with a prefix of min_chars-1 fails

GET test_prefix/_search
{"query":{"prefix":{"t": "t"}}}

GET test_prefix/_search
{"query":{"prefix":{"t": "the"}}}

GET test_prefix/_search
{"query":{"prefix":{"t": "th"}}}

simple_query_string also fails

GET test_prefix/_search
{"query":{"simple_query_string":{"fields":["t"], "query":"th*"}}}

The regexp is the only option to do the search, but i could not find information on the documentation if regexp queries take advantage of the index_prefix

GET test_prefix/_search
{"query":{"regexp": {
      "t": {
        "value": "th.*",
        "flags": "ALL",
        "case_insensitive": true,
        "max_determinized_states": 10000,
        "rewrite": "constant_score"
      }
    }}}

Output

the error produced is the next

{
  "error" : {
    "root_cause" : [
      {
        "type" : "null_pointer_exception",
        "reason" : "Cannot invoke \"org.apache.lucene.search.MultiTermQuery$RewriteMethod.rewrite(org.apache.lucene.index.IndexReader, org.apache.lucene.search.MultiTermQuery)\" because \"this.rewriteMethod\" is null"
      }
    ],
    "type" : "search_phase_execution_exception",
    "reason" : "all shards failed",
    "phase" : "query",
    "grouped" : true,
    "failed_shards" : [
      {
        "shard" : 0,
        "index" : "test_prefix",
        "node" : "KPamBItNTOi2hLRNTFcTMw",
        "reason" : {
          "type" : "null_pointer_exception",
          "reason" : "Cannot invoke \"org.apache.lucene.search.MultiTermQuery$RewriteMethod.rewrite(org.apache.lucene.index.IndexReader, org.apache.lucene.search.MultiTermQuery)\" because \"this.rewriteMethod\" is null"
        }
      }
    ],
    "caused_by" : {
      "type" : "null_pointer_exception",
      "reason" : "Cannot invoke \"org.apache.lucene.search.MultiTermQuery$RewriteMethod.rewrite(org.apache.lucene.index.IndexReader, org.apache.lucene.search.MultiTermQuery)\" because \"this.rewriteMethod\" is null",
      "caused_by" : {
        "type" : "null_pointer_exception",
        "reason" : "Cannot invoke \"org.apache.lucene.search.MultiTermQuery$RewriteMethod.rewrite(org.apache.lucene.index.IndexReader, org.apache.lucene.search.MultiTermQuery)\" because \"this.rewriteMethod\" is null"
      }
    }
  },
  "status" : 500
}

[elasticsearchmachine]

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