Add filter to remove search weighting engine

[rebeccahum]

Description of the Change

Add a filter, so there's an option to turn off the weighting engine.

Alternate Designs

#2512, but there are too many moving parts.

Benefits

The user will be able to simplify the below query (i.e. using the example searching for "hello"):

{
  "from": 0,
  "size": 10,
  "sort": [
    {
      "_score": {
        "order": "desc"
      }
    }
  ],
  "query": {
    "function_score": {
      "query": {
        "bool": {
          "should": [
            {
              "bool": {
                "must": [
                  {
                    "bool": {
                      "must": [
                        {
                          "multi_match": {
                            "query": "hello",
                            "type": "phrase",
                            "fields": [
                              "post_title^1",
                              "post_excerpt^1",
                              "post_content^1",
                              "post_author.display_name^1",
                              "terms.post_tag.name^1",
                              "terms.category.name^1",
                              "terms.ep_custom_result.name^9999"
                            ],
                            "boost": 3,
                            "operator": "AND"
                          }
                        },
                        {
                          "multi_match": {
                            "query": "hello",
                            "fields": [
                              "post_title^1",
                              "post_excerpt^1",
                              "post_content^1",
                              "post_author.display_name^1",
                              "terms.post_tag.name^1",
                              "terms.category.name^1",
                              "terms.ep_custom_result.name^9999"
                            ],
                            "type": "phrase",
                            "slop": 5
                          }
                        }
                      ]
                    }
                  }
                ],
                "filter": [
                  {
                    "match": {
                      "post_type.raw": "post"
                    }
                  }
                ]
              }
            },
            {
              "bool": {
                "must": [
                  {
                    "bool": {
                      "must": [
                        {
                          "multi_match": {
                            "query": "hello",
                            "type": "phrase",
                            "fields": [
                              "post_title^1",
                              "post_excerpt^1",
                              "post_content^1",
                              "post_author.display_name^1",
                              "terms.ep_custom_result.name^9999"
                            ],
                            "boost": 3,
                            "operator": "AND"
                          }
                        },
                        {
                          "multi_match": {
                            "query": "hello",
                            "fields": [
                              "post_title^1",
                              "post_excerpt^1",
                              "post_content^1",
                              "post_author.display_name^1",
                              "terms.ep_custom_result.name^9999"
                            ],
                            "type": "phrase",
                            "slop": 5
                          }
                        }
                      ]
                    }
                  }
                ],
                "filter": [
                  {
                    "match": {
                      "post_type.raw": "page"
                    }
                  }
                ]
              }
            }
          ]
        }
      },
      "functions": [
        {
          "gauss": {
            "post_date_gmt": {
              "scale": "360d",
              "decay": 0.9,
              "offset": "0d"
            }
          }
        },
        {
          "weight": 0.001
        }
      ],
      "score_mode": "multiply",
      "boost_mode": "multiply"
    }
  },
  "post_filter": {
    "bool": {
      "must": [
        {
          "terms": {
            "post_type.raw": [
              "post",
              "page"
            ]
          }
        },
        {
          "terms": {
            "post_status": [
              "publish"
            ]
          }
        }
      ]
    }
  },
  "track_total_hits": true
}

Compared to the simplified query:

{
  "from": 0,
  "size": 10,
  "sort": [
    {
      "_score": {
        "order": "desc"
      }
    }
  ],
  "query": {
    "function_score": {
      "query": {
        "bool": {
          "must": [
            {
              "multi_match": {
                "query": "hello",
                "type": "phrase",
                "fields": [
                  "post_title",
                  "post_excerpt",
                  "post_content"
                ],
                "boost": 3,
                "operator": "AND"
              }
            },
            {
              "multi_match": {
                "query": "hello",
                "fields": [
                  "post_title",
                  "post_excerpt",
                  "post_content"
                ],
                "type": "phrase",
                "slop": 5
              }
            }
          ]
        }
      },
      "functions": [
        {
          "gauss": {
            "post_date_gmt": {
              "scale": "360d",
              "decay": 0.9,
              "offset": "0d"
            }
          }
        },
        {
          "weight": 0.001
        }
      ],
      "score_mode": "multiply",
      "boost_mode": "multiply"
    }
  },
  "post_filter": {
    "bool": {
      "must": [
        {
          "terms": {
            "post_type.raw": [
              "post",
              "page"
            ]
          }
        },
        {
          "terms": {
            "post_status": [
              "publish"
            ]
          }
        }
      ]
    }
  },
  "track_total_hits": true
}

Possible Drawbacks

None that I can think of.

Verification Process

Use add_filter( 'ep_load_search_weighting', '__return_false' ); and observe the change in ES query.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Changelog Entry

Added: Filter ep_load_search_weighting to disable search weighting engine.

[felipeelia]

Hey @rebeccahum, thanks for the PR! Do you mind moving the filter to the Weighting->setup() method (early returning if true) and also adding the doc block? This will be introduced in 4.0.0 (for the @since tag.) Thanks!

[rebeccahum]

@felipeelia Done!

[felipeelia]

Thanks @rebeccahum! As we need it merged to 4.x.x rather than develop I'll work on that conflict and merge it asap.