Smart Answers Detailed Pipeline Setup

Index pipeline setup
- Model input transformation script
- Model output transformation script
Query pipeline setup

Typically, you can use the default pipelines included with Fusion AI. This topic provides information you can use to customize these pipelines. See also Configure The Smart Answers Pipelines.

"question-answering" index pipeline

question-answering default index pipeline

Machine Learning

"question-answering" query pipeline

question-answering default query pipeline

Index pipeline setup

Stages in the default "question-answering" index pipeline

question-answering default index pipeline

Typically, only one custom index stage needs to be configured in your index pipeline:

the Machine Learning index stage.

Tip	If you are using a dynamic schema, make sure this stage is added after the Solr Dynamic Field Name Mapping stage.

There are several required parameters: * Model ID - The ID of the model. * Model input transformation script - Configures input to the model . documentFeatureField - The text field to encode to the dense vectors, such as answer_t or body_t (the default value). * Model output transformation script - Maps model output into the document fields. compressedVectorField - The field that stores compressed dense vectors. Fusion compresses dense vectors to strings. The compressed version is used as the default to get better query runtime performance. Default value: compressed_document_vector_s. keepUncompressedVector - Specifies should uncompressed vector be stored in Solr. Uncompressed vectors require more storage and it’s not recommended to return it during the query time as it might affect query performance. Default value: false vectorField - The field that stores uncompressed dense vectors. It’s stored only if keepUncompressedVector is set to true. Default value: document_vector_ds clustersField - The field that stores answer clusters IDs. Default value: document_clusters_ss. distancesField - The field that stores distances between a document vector and its closest cluster centers. This can be used for eDiscovery purposes. For example, we can explore the clusters by sorting documents in ascending order based on this distance to clusters centers. Default value: document_distances_ds. ** numClusters - This value denotes how many clusters each document can belong to. In most cases it’s better to use just one or two clusters, since we already provide a query pipeline stage to find multiple clusters at query time.

+ NOTE: This value should be less than or equal to the number of clusters specified in the model training. Default value: 1.

Model input transformation script

/*
Name of the document field to feed into the encoder.
*/
var documentFeatureField = "body_t"

/*
Model input construction.
*/
var modelInput = new java.util.HashMap()
modelInput.put("text", doc.getFirstFieldValue(documentFeatureField))
modelInput.put("pipeline", "index")
modelInput.put("compress", "true")
modelInput.put("unidecode", "true")
modelInput.put("lowercase", "false")

modelInput

Model output transformation script

/*
Name of the field to store the compressed encoded vector in the document.

Compressed vector field will be added to the document only if `compress = "true"` was
passed into the `modelInput`.
*/
var compressedVectorField = "compressed_document_vector_s"

/*
Name of the field to store the uncompressed encoded vector in the document.

By default uncompressed vector wouldn't be added to the document.
Change `keepUncompressedVector` to true if you want to keep uncompressed vector.
*/
var keepUncompressedVector = false
var vectorField = "document_vector_ds"

/*
Clustering fields that keep cluster IDs and distances to the clusters.
NOTE: Only models from the training module will provide clustering fields.
*/
var clustersField = "document_clusters_is"
var distancesField = "document_distances_ds"

/*
Variable `numClusters` specifies how many top clusters should be kept for the document.
The value should be less or equal to the value in the training configuration.
The default value of 1 is a good choice for most cases.
*/
var numClusters = 1

/*
Model output parsing.
*/
if (modelOutput.containsKey("compressed_vector")) {
 doc.addField(compressedVectorField, modelOutput.get("compressed_vector")[0])
}

if (keepUncompressedVector) {
 doc.addField(vectorField, modelOutput.get("vector"))
}

if (numClusters > 0 && modelOutput.containsKey("clusters")) {
 doc.addField(clustersField, modelOutput.get("clusters").subList(0, numClusters))
 doc.addField(distancesField, modelOutput.get("distances").subList(0, numClusters))
}

Query pipeline setup

Stages in the default "question-answering" query pipeline

question-answering default query pipeline

In the "question-answering" query pipeline, all stages (except the Solr Query stage) can be tuned for better Smart Answers:

Query Fields
Rewrite Pagination Parameters for Ranking
Filter Stop Words
Machine Learning
Escape Query
Query-Document Vectors Distance
Computer Mathematical Expression
Result Document Field Sorting

You can also configure the number of clusters used in deep encoding.

The Query Fields stage

The first stage is Query Fields which should have one main parameter specified:

Return Fields - Since documents should be retrieved with vectors and clusters, make sure to include the documents’ Vector Field and Clusters Field, which are compressed_document_vector_s and document_clusters_ss by default.

The Rewrite Pagination Parameters for Reranking stage

The Rewrite Pagination Parameters for Reranking query stage is used to specify how many results from Solr should be used to create a pool of candidates for further re-ranking via model. It’s done under the hood, so users would still see the number of results controlled by "start" and "rows" query parameters.

Number of Results - Number of results to request from Solr, to be re-ranked by downstream stages. Default value: 500. This parameter affects both results accuracy and query time performance. Increasing the number can lead to better accuracy but worse query time performance and vice versa.

Note
This parameter can be dynamically overwritten by rowsFromSolrToRerank raw query parameter in the request.

The Filter Stop Words stage

When limited data is provided to train FAQ or coldstart models, the model may not be able to learn the weights of stop words accurately. Especially when using Solr to retrieve the top x results (if Number of Clusters is set to 0 in the Machine Learning stage), stop words may have high impact on Solr. User can use this stage to provide customized stop words list by providing them in Words to filter part of the stage.

See Filter Stop Words for reference information. See also Best Practices.

The Machine Learning ("Query Encoding") stage

The Machine Learning query stage configuration is very similar to the index stage.

Tip	If you are using the cluster retrieval configuration in Example 1, then this stage should be located before the Solr Query stage.

The important configuration keys are as follows:

Model ID - This is the model deployment name you chose when you configured the model training job

Model output transformation script - Maps model output into the document fields

documentClustersField - Document clusters Solr field name. If clustering is used then Filter Query is constructed against this field to return all documents that have the same clusters as the query. This concept is similar to Inverted File Index (IVF).

Note
Only models from the training module support clustering. Default value: document_clusters_is

numClusters - The number of clusters that should be used for each query. This value should be less than or equal to the number of clusters specified in the model training. Default value: 0

Note	By default it’s set to 0 which means that clustering isn’t used. Fusion returns a pool of candidates based solely on the Solr score, then performs re-ranking. If you want to use clustering, value 10 is a good choice for most cases.

Note	If the number of clusters is greater than 0 and the search term is `:`, there will be a limited number of documents shown in the result rather than showing the whole collection. That’s because `:` will be assigned to certain clusters.

Model input transformation script

/*
Model input construction.
*/
var modelInput = new java.util.HashMap()
modelInput.put("text", request.getFirstParam("q"))
modelInput.put("pipeline", "query")
modelInput.put("compress", "false")
modelInput.put("unidecode", "true")
modelInput.put("lowercase", "false")

modelInput

Model output transformation script

/*
Document clusters Solr field name. If clustering is used then Filter Query is
constructed against this field to return all documents that have the same clusters as
query. This concept is similar to Inverted File Index (IVF).

NOTE: Only models from the training module support clustering.
*/
var documentClustersField = "document_clusters_is"

/*
Variable `numClusters` specifies how many top clusters should be used for each query.
The value should be less or equal to the value in the training configuration.
By default it's set to 0 which means that clustering isn't used. If you want to use
clustering, value 10 is a good choice for most cases.
*/
var numClusters = 0

/*
Model output parsing.
*/
var queryVector = modelOutput.get("vector").stream().mapToDouble(function(d){return d}).toArray()
context.put("query_vector", queryVector)

if (numClusters > 0 && modelOutput.containsKey("clusters")) {
   clusters = Java.from(modelOutput.get("clusters").subList(0, numClusters))
   if (clusters.length > 1) {
     fq = documentClustersField+":("+clusters.join(' OR ')+")"
   } else {
     fq = documentClustersField+":"+clusters[0]
   }

   request.putSingleParam("q", "*:*")
   request.addParam("fq", fq)
}

The Escape Query stage

The Escape Query query stage escapes Lucene/Solr reserved characters in a query. In the Smart Answers use case, queries are natural-language questions. They tend to be longer than regular queries and with punctuation which we don’t want to interpret as Lucene/Solr query operators.

The Query-Document Vectors Distance stage

The Query-Document Vectors Distance query stage computes the distance between a query vector and each candidate document vector. It should be added after the Solr Query stage.

Query Vector Context Key - The context key which stores dense vectors. It should be set to the same value as _Vector Context Key _in the Machine Learning stage. Default value: query_vector.
Document Vector Field - The field which stores dense vectors or their compressed representations. It should be the same as _Vector Field _in Machine Learning stage. Default: compressed_document_vector_s.
Keep document vector field - This option allows you to keep or drop returned document vectors. In most cases it makes sense to drop document vectors after computing vector distances, to improve run time performance. Default: False (unchecked).
Distance Type - Choose one of the supported distance types. For a FAQ solution, cosine_similarity is recommended, which produces values with a maximum value of 1. Higher value means higher similarity. Default: cosine_similarity.
Document Vectors Distance Field - The result document field that contains the distance between its vector and the query vector. Default: vectors_distance.

The Compute Mathematical Expression stage

We can use the Compute Mathematical Expression query stage to combine the Solr score with the vectors similarity score to borrow Solr’s keywords matching capabilities. This stage should be set before the Result Document Field Sorting stage. Result field name in this stage and Sort field in the Result Document Field Sorting stage should be set to the same value.

Math expression - Specify a mathematical formula for combining the Solr score and the vector similarity score. Note that Solr scores do not have an upper bound, so it is best to rescale it by using the max_score value, which is the max Solr score from all returned docs. vectors_distance is the cosine similarity in our case and it already has an upper bound of 1.0. The complete list of supported mathematical expressions is listed in the Oracle documentation.

Default: 0.3 * score / max_score + 0.7 * vectors_distance

Note	We recommend adjusting the ratios 0.3 and 0.7 to other values based on query-time evaluation results (mentioned in the section above). Feel free to try other math expressions (such as log10) to scale the Solr score as well.

Result field name - The document field name that contains the combined score. The same value should be set in the Result Document Field Sorting stage, in the Sort Field parameter. Default: ensemble_score

The Result Document Field Sorting stage

Finally, the Result Document Field Sorting stage sorts results based on vector distances obtained from the previous Vectors distance per Query/Document stage or ensemble score from Compute mathematical expression stage.

Sort Field - The field to use for document sorting. Default value: ensemble_score
Sort order - The sorting order: (asc)ending or (desc)ending. If cosine_similarity is used with higher values meaning higher similarity, then this should be set to desc. Default: desc.

Configuring the number of clusters

Another important parameter to choose is the Number of clusters parameter in the Machine Learning stage in the query pipeline. There are two options for utilizing the dense vectors from a query pipeline:

If set Number of clusters parameter to 0 (default option), then we use Solr to return the top x results, then re-rank using vector cosine similarity, or combine the Solr score with the vector score using our Compute mathematical expression stage. If you choose this option, then adjust Number of Results parameter (Default value 500) in the Rewrite Pagination Parameters for Reranking stage in the query pipeline. This parameter controls how many documents to be returned from Solr to Fusion and re-ranked under the hood. You can adjust this parameter to find a good balance between relevancy and query speed.
If you set the Number of clusters parameter to a value x greater than 0, when a query comes in, Fusion transfers the query into a dense vector and find the closest x clusters to which the query belongs. The pipeline then obtains documents from the same clusters as query and re-ranks them based on the vector cosine similarity between the query and the indexed answers/questions. The good default values can be 1 cluster per document and 10 clusters per query.

Documents from the clusters might be obtained in the following ways: * By using Solr search. Then search space is narrowed by both clusters and Solr. And Solr score might be used in the ensemble in the same way as in the first option described above. * By using only clusters. Then all documents from certain clusters are retrieved for re-ranking. Solr doesn’t narrow the search space, but it’s also not used for ensemble.

Comprehensive evaluation should be done to decide which approach to use.