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Fusion 5.9
    Fusion 5.9

    Chunking Neural Hybrid Query Stage

    The Chunking Neural Hybrid Query stage performs hybrid lexical-semantic search that combines BM25-type lexical search with KNN dense vector search via Solr. This stage differs from the Neural Hybrid Stage because it supports chunking.

    Not sure which hybrid query stage is right for you? Read about the differences between the hybrid query stages.

    This feature is only available in Fusion 5.9.x for versions 5.9.12 and later.

    Click Get Started below to see how to enable chunking in Fusion:

    About the Lexical Query Squash Factor

    The Lexical Query Squash Factor field lets you input a value that squashes the lexical query scores from 0..inf to 0..1. This setting helps prevent the lexical query from dominating the final score, and normalizes the score into a range that works well with vector similarity scores. Additionally, it helps prevent the vanishing gradient problem, which occurs when very high lexical scores are mapped to values extremely close to 1, such as 0.99999999. During the hybrid search calculation, these near-1 values can cause the system to lose sensitivity to subtle differences in lexical relevance, effectively 'squashing' the gradient and reducing the impact of lexical scoring.

    Lucidworks recommends setting the Lexical Query Squash Factor to the inverse of the maximum lexical score observed across your queries. This helps balance the impact of lexical and vector scores, leading to more accurate and nuanced search results.

    Prefiltering

    Prefiltering is a technique that can improve performance and accuracy by filtering documents before applying the algorithm, reducing the number of documents that need to be processed. This is especially effective with the KNN algorithm.

    Prefiltering is disabled by default. To enable it, uncheck Block pre-filtering in this stage.

    When prefiltering is enabled, you can configure the filters using one or more of these methods:

    • Security filters

      You can use security filters as prefilters by placing the Graph Security Trimming Stage after this one in the pipeline. Then Fusion uses the security trimming filter as a prefilter.

    • JavaScript

      When prefiltering is enabled, this stage adds a preFilterKey object to the Javascript ctx object. You can place a Javascript stage after this one and use it to access the preFilterKey object, as in this example:

      var QueryRequestAndResponse = Java.type('com.lucidworks.apollo.pipeline.query.QueryRequestAndResponse');
if(ctx.hasProperty("preFilterKey")) {
  var preFilter = ctx.getProperty("preFilterKey");
  var wrapper = QueryRequestAndResponse.create(request,response,0)
  preFilter.addFilter(wrapper, 'id:* OR foo_s:bar');
}

    • Additional Query Parameters stage

      If you do not want to create a JavaScript stage, you can create additional query parameters to prefilter the documents to be processed by using what the previous JavaScript example adds to the request. The following example uses a single prefilter:

      "fq" = "{!bool filter=$vectorPreFilter}"
"vectorPreFilter" = "EXAMPLE_FILTER"

      The following example uses multiple prefilters:

      "fq": "{!bool filter=$filterClauses}",
"vectorPreFilter": "{!bool should=$filterClauses}",
"filterClauses": ["id:EXAMPLE_FILTER1","id:EXAMPLE_FILTER2"]

    Query pipeline stage condition examples

    Stages can be triggered conditionally when a script in the Condition field evaluates to true. Some examples are shown below.

    Run this stage only for mobile clients:

    params.deviceType === "mobile"

    Run this stage when debugging is enabled:

    params.debug === "true"

    Run this stage when the query includes a specific term:

    params.q && params.q.includes("sale")

    Run this stage when multiple conditions are met:

    request.hasParam("fusion-user-name") && request.getFirstParam("fusion-user-name").equals("SuperUser");
!request.hasParam("isFusionPluginQuery")

    The first condition checks that the request parameter "fusion-user-name" is present and has the value "SuperUser". The second condition checks that the request parameter "isFusionPluginQuery" is not present.

    Configuration

    When entering configuration values in the UI, use unescaped characters, such as \t for the tab character. When entering configuration values in the API, use escaped characters, such as \\t for the tab character.

    Hybrid of Multi-Vector and Lexical Search. Will be skipped if query string is blank or wildcard (* or *:*). Note this will not work well if the incoming q parameter is a Solr query parser string (e.g. field_t:foo) rather than a raw user query string. Note: The resulting query will ALWAYS be written to <request.params.q>.

    skip - boolean

    Set to true to skip this stage.

    Default: false

    label - string

    A unique label for this stage.

    <= 255 characters

    condition - string

    Define a conditional script that must result in true or false. This can be used to determine if the stage should process or not.

    lexicalQuery - stringrequired

    The lexical query itself is retrieved from here. This field supports Template Expressions such as '<request.params.q>' to evaluate the original user query.

    Default: <request.params.q>

    lexicalWeight - numberrequired

    Relative weight of the lexical query. If this value is 0, no re-ranking will be applied using the lexical query scores.

    <= 10

    exclusiveMaximum: false

    Default: 0.1

    lexicalSquash - numberrequired

    The squash factor for the lexical query. This value is used to squash the lexical query scores from 0..inf to 0..1, which can help to prevent the lexical query from dominating the final score. NOTE: A good value here would be the inverse of the lexical maximum score across all queries for the given collection. NOTE: If this value is 0.0, the resulting squashed lexical scores will ALL by 0.0, resulting in lexical recall but vector scoring.

    <= 10

    exclusiveMaximum: false

    Default: 0.1

    vectorQueryField - stringrequired

    The name of the Solr field for knn vector search.

    vector - stringrequired

    The Vector itself is retrieved from here. This field supports Template Expressions such as '<ctx.vector>' to evaluate the context variable resulting from a previous stage, such as the Vectorize Query via Lucidworks AI stage.

    Default: <ctx.vector>

    vectorWeight - numberrequired

    Relative weight of the vector query.

    >= 0.001

    <= 10

    exclusiveMinimum: false

    exclusiveMaximum: false

    Default: 0.9

    minReturnSim - numberrequired

    The minimum vector similarity value to qualify as a match from the Vector portion of the hybrid query.

    <= 1

    exclusiveMaximum: false

    Default: 0.5

    minTraverseSim - numberrequired

    The minimum vector similarity value to use when walking the graph during the Vector portion of the hybrid query. Must be lower than, or equal to, the Min Return Vector Similarity

    <= 1

    exclusiveMaximum: false

    Default: 0.5

    vecSimForLexOnly - boolean

    Compute the vector similarity score for documents that are not in the vector result set but are in the lexical result set.

    Default: true

    vecPreFilterBoolean - boolean

    Checkbox to indicate whether or not to prevent pre-filtering. If checked, preFilter="" will be added to the vector query, which will prevent pre-filtering from being applied to the query.

    Default: true