Introduces query parameter ef_search for NMSLIB

[shatejas]

Description

Integrates NMSLIB with ef_search

curl -XGET "http://localhost:9200/nmslib-hnsw-index/_search" -H 'Content-Type: application/json' -d'
{
  "query": {
    "knn": {
      "nmslib_vector": {
        "vector": [2, 3, 5],
        "k": 2,
        "method_parameters" : {
            "ef_search" : 200
        }
        }
      }
    }
  }'

{
  "took": 6,
  "timed_out": false,
  "_shards": {
    "total": 1,
    "successful": 1,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": {
      "value": 2,
      "relation": "eq"
    },
    "max_score": 0.11918951,
    "hits": [
      {
        "_index": "nmslib-hnsw-index",
        "_id": "3",
        "_score": 0.11918951,
        "_source": {
          "nmslib_vector": [
            3.5,
            4.5,
            3.3
          ],
          "price": 12.9
        }
      },
      {
        "_index": "nmslib-hnsw-index",
        "_id": "2",
        "_score": 0.10706638,
        "_source": {
          "nmslib_vector": [
            2.5,
            3.5,
            2.2
          ],
          "price": 7.1
        }
      }
    ]
  }
}

Issues Resolved

#1537

Check List - Pending

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
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[shatejas]

Here is the diff for this patch

[heemin32]

Shouldn't there be a unit test for this change in nmslib code base?

[shatejas]

There are no unit test in the entire lib. There is no way to test it out unless we end up writing it for the entire search which will become a heavy lift.

There is an integ test though and I tested it out using this code shatejas/nmslib@c5dd7cd. I did not add it in the patch because its not generic enough. There are some validations in the hnsw code which is making it difficult to add more parameters in the integ test

@heemin32

[navneet1v]

@shatejas please fix the failing GH actions

[jmazanec15]

lgtm - waiting on CI

[shatejas]

@shatejas please fix the failing GH actions

The build in linux is failing with the same failure as main

[heemin32]

Shouldn't there be a unit test for this change in nmslib code base?

[heemin32]

Build failure will be fixed in #1748