[Feature Request] /msearch API fails if any query is malformed

[colinking]

Is your feature request related to a problem? Please describe

In the example below, we run two queries on the ecommerce dataset via an /msearch request. The first query is valid, but the second query is malformed (due to the null value). The entire /msearch API fails with a 400 error and we do not get a response for the first query.

curl -s "http://localhost:3955/_msearch" -H 'Content-Type: application/json' -d'
{ "index": "ecommerce"}
{ "query": { "term": {"customer_first_name.keyword": "Jason"} }, "from": 0, "size": 1 }
{ "index": "ecommerce"}
{ "query": { "term": {"customer_first_name.keyword": null } }, "from": 0, "size": 1 }
' | jq .
{
  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception",
        "reason": "field name is null or empty"
      }
    ],
    "type": "illegal_argument_exception",
    "reason": "field name is null or empty"
  },
  "status": 400
}

Contrast this with what happens if the second query is malformed in a different way, such as referencing an index that doesn't exist. In this case, the /msearch API returns a response for the first query, and an error for the second query.

curl -s "http://localhost:3955/_msearch" -H 'Content-Type: application/json' -d'
{ "index": "ecommerce"}
{ "query": { "term": {"customer_first_name.keyword": "Jason"} }, "from": 0, "size": 1 }
{ "index": "ecommerce2"}
{ "query": { "term": {"customer_first_name.keyword": "Selena" } }, "from": 0, "size": 1 }
' | jq .
{
  "took": 4,
  "responses": [
    {
      "took": 4,
      "timed_out": false,
      "_shards": {
        "total": 1,
        "successful": 1,
        "skipped": 0,
        "failed": 0
      },
      "hits": {
        "total": {
          "value": 65,
          "relation": "eq"
        },
        "max_score": 4.268148,
        "hits": [
          {
            "_index": "ecommerce",
            "_id": "89",
            "_score": 4.268148,
            "_source": {
              "category": [
                "Men's Clothing",
                "Men's Accessories"
              ],
              "currency": "EUR",
              "customer_first_name": "Jason",
              "customer_full_name": "Jason Jacobs",
              "customer_gender": "MALE",
              "customer_id": 16,
              "customer_last_name": "Jacobs",
              "customer_phone": "",
              "day_of_week": "Monday",
              "day_of_week_i": 0,
              "email": "[email protected]",
              "manufacturer": [
                "Elitelligence"
              ],
              "order_date": "2016-12-19T20:09:36+00:00",
              "order_id": 575797,
              "products": [
                {
                  "base_price": 14.99,
                  "discount_percentage": 0,
                  "quantity": 1,
                  "manufacturer": "Elitelligence",
                  "tax_amount": 0,
                  "product_id": 18217,
                  "category": "Men's Clothing",
                  "sku": "ZO0555205552",
                  "taxless_price": 14.99,
                  "unit_discount_amount": 0,
                  "min_price": 7.2,
                  "_id": "sold_product_575797_18217",
                  "discount_amount": 0,
                  "created_on": "2016-12-19T20:09:36+00:00",
                  "product_name": "Long sleeved top - dark blue/pink",
                  "price": 14.99,
                  "taxful_price": 14.99,
                  "base_unit_price": 14.99
                },
                {
                  "base_price": 10.99,
                  "discount_percentage": 0,
                  "quantity": 1,
                  "manufacturer": "Elitelligence",
                  "tax_amount": 0,
                  "product_id": 21624,
                  "category": "Men's Accessories",
                  "sku": "ZO0602206022",
                  "taxless_price": 10.99,
                  "unit_discount_amount": 0,
                  "min_price": 5.17,
                  "_id": "sold_product_575797_21624",
                  "discount_amount": 0,
                  "created_on": "2016-12-19T20:09:36+00:00",
                  "product_name": "Wallet - brown",
                  "price": 10.99,
                  "taxful_price": 10.99,
                  "base_unit_price": 10.99
                }
              ],
              "sku": [
                "ZO0555205552",
                "ZO0602206022"
              ],
              "taxful_total_price": 25.98,
              "taxless_total_price": 25.98,
              "total_quantity": 2,
              "total_unique_products": 2,
              "type": "order",
              "user": "jason",
              "geoip": {
                "country_iso_code": "US",
                "location": {
                  "lon": -74,
                  "lat": 40.8
                },
                "region_name": "New York",
                "continent_name": "North America",
                "city_name": "New York"
              },
              "event": {
                "dataset": "sample_ecommerce"
              }
            }
          }
        ]
      },
      "status": 200
    },
    {
      "error": {
        "root_cause": [
          {
            "type": "index_not_found_exception",
            "reason": "no such index [ecommerce2]",
            "index": "ecommerce2",
            "resource.id": "ecommerce2",
            "resource.type": "index_or_alias",
            "index_uuid": "_na_"
          }
        ],
        "type": "index_not_found_exception",
        "reason": "no such index [ecommerce2]",
        "index": "ecommerce2",
        "resource.id": "ecommerce2",
        "resource.type": "index_or_alias",
        "index_uuid": "_na_"
      },
      "status": 404
    }
  ]
}

In both cases, only one of the two queries is malformed. However, only the second scenario gives us a partial response. This contrasts with the docs, which state: " OpenSearch executes each search independently, so the failure of one doesn’t affect the others."

Describe the solution you'd like

I would like the /msearch API to return the following response for the first scenario. This would give us a partial response, and would prevent the failure of the second query from impacting the first query.

curl -s "http://localhost:3955/_msearch" -H 'Content-Type: application/json' -d'
{ "index": "ecommerce"}
{ "query": { "term": {"customer_first_name.keyword": "Jason"} }, "from": 0, "size": 1 }
{ "index": "ecommerce"}
{ "query": { "term": {"customer_first_name.keyword": null } }, "from": 0, "size": 1 }
' | jq .
{
  "took": 4,
  "responses": [
    {
      "took": 4,
      "timed_out": false,
      "_shards": {
        "total": 1,
        "successful": 1,
        "skipped": 0,
        "failed": 0
      },
      "hits": {
        "total": {
          "value": 65,
          "relation": "eq"
        },
        "max_score": 4.268148,
        "hits": [
          {
            "_index": "ecommerce",
            "_id": "89",
            "_score": 4.268148,
            "_source": {
              "category": [
                "Men's Clothing",
                "Men's Accessories"
              ],
              "currency": "EUR",
              "customer_first_name": "Jason",
              "customer_full_name": "Jason Jacobs",
              "customer_gender": "MALE",
              "customer_id": 16,
              "customer_last_name": "Jacobs",
              "customer_phone": "",
              "day_of_week": "Monday",
              "day_of_week_i": 0,
              "email": "[email protected]",
              "manufacturer": [
                "Elitelligence"
              ],
              "order_date": "2016-12-19T20:09:36+00:00",
              "order_id": 575797,
              "products": [
                {
                  "base_price": 14.99,
                  "discount_percentage": 0,
                  "quantity": 1,
                  "manufacturer": "Elitelligence",
                  "tax_amount": 0,
                  "product_id": 18217,
                  "category": "Men's Clothing",
                  "sku": "ZO0555205552",
                  "taxless_price": 14.99,
                  "unit_discount_amount": 0,
                  "min_price": 7.2,
                  "_id": "sold_product_575797_18217",
                  "discount_amount": 0,
                  "created_on": "2016-12-19T20:09:36+00:00",
                  "product_name": "Long sleeved top - dark blue/pink",
                  "price": 14.99,
                  "taxful_price": 14.99,
                  "base_unit_price": 14.99
                },
                {
                  "base_price": 10.99,
                  "discount_percentage": 0,
                  "quantity": 1,
                  "manufacturer": "Elitelligence",
                  "tax_amount": 0,
                  "product_id": 21624,
                  "category": "Men's Accessories",
                  "sku": "ZO0602206022",
                  "taxless_price": 10.99,
                  "unit_discount_amount": 0,
                  "min_price": 5.17,
                  "_id": "sold_product_575797_21624",
                  "discount_amount": 0,
                  "created_on": "2016-12-19T20:09:36+00:00",
                  "product_name": "Wallet - brown",
                  "price": 10.99,
                  "taxful_price": 10.99,
                  "base_unit_price": 10.99
                }
              ],
              "sku": [
                "ZO0555205552",
                "ZO0602206022"
              ],
              "taxful_total_price": 25.98,
              "taxless_total_price": 25.98,
              "total_quantity": 2,
              "total_unique_products": 2,
              "type": "order",
              "user": "jason",
              "geoip": {
                "country_iso_code": "US",
                "location": {
                  "lon": -74,
                  "lat": 40.8
                },
                "region_name": "New York",
                "continent_name": "North America",
                "city_name": "New York"
              },
              "event": {
                "dataset": "sample_ecommerce"
              }
            }
          }
        ]
      },
      "status": 200
    },
    {
      "error": {
        "root_cause": [
          {
            "type": "illegal_argument_exception",
            "reason": "field name is null or empty"
          }
        ],
        "type": "illegal_argument_exception",
        "reason": "field name is null or empty"
      },
      "status": 400
    }
  ]
}

If this is considered a breaking change, I'd propose making this behavior opt-in via a boolean request argument.

Related component

Search

Describe alternatives you've considered

We could call the Validate Query on each of the queries we want to execute, but that adds latency to our overall search performance. A bulk version of this API would help, but we'd still prefer if this happened automatically within msearch.

Additional context

The examples above were tested on OpenSearch 2.18 using the dataset from here.