- All Implemented Interfaces:
public class NGramSearcher extends SearcherHandles NGram indexes by splitting query terms to them into grams and combining summary field values from such fields into the original text.
This declares it must be placed after Juniper searchers because it assumes Juniper token separators (which are returned on bolding) are not replaced by highlight tags when this is run (and "after" means "before" from the point of view of the result).
Constructors Constructor Description
All Methods Instance Methods Concrete Methods Modifier and Type Method Description
createGramRoot(Query query)Creates the root of the query subtree which will contain the grams to match, called by
splitToGrams(com.yahoo.prelude.query.Item, java.lang.String, int, com.yahoo.search.Query).
fill(Result result, java.lang.String summaryClass, Execution execution)Fill hit properties with data using the given summary class.
getGramSplitter()Returns the (thread-safe) object to use to split the query text into grams.
search(Query query, Execution execution)Override this to implement your searcher.
splitToGrams(Item term, java.lang.String text, int gramSize, Query query)Splits the given item into n-grams and adds them as a CompositeItem containing WordItems searching the index of the input term.
Methods inherited from class com.yahoo.component.chain.ChainedComponent
getAnnotatedDependencies, getDefaultAnnotatedDependencies, getDependencies, initDependencies
Methods inherited from class com.yahoo.component.AbstractComponent
clone, compareTo, deconstruct, getClassName, getId, getIdString, hasInitializedId, initId, isDeconstructable, setIsDeconstructable
searchDescription copied from class:
SearcherOverride this to implement your searcher.
Searcher implementation subclasses will, depending on their type of logic, do one of the following:
- Query processors: Access the query, then call execution.search and return the result
- Result processors: Call execution.search to get the result, access it and return
- Sources (which produces results): Create a result, add the desired hits and return it.
- Federators (which forwards the search to multiple subchains): Call search on the desired subchains in parallel and get the results. Combine the results to one and return it.
- Workflows: Call execution.search as many times as desired, using different queries. Eventually return a result.
Hits come in two kinds - concrete hits are actual content of the kind requested by the user, meta hits are hits which provides information about the collection of hits, on the query, the service and so on.
The query specifies a window into a larger result list that must be returned from the searcher through hits and offset; Searchers which returns list of hits in the top level in the result must return at least hits number of hits (or if impossible; all that are available), starting at the given offset. In addition, searchers are allowed to return any number of meta hits (although this number is expected to be low). For hits contained in nested hit groups, the concept of a window defined by hits and offset is not well defined and does not apply.
Error handling in searchers:
- Unexpected events: Throw any RuntimeException. This query will fail with the exception message, and the error will be logged
- Expected events: Create (new Result(Query, ErrorMessage) or add result.setErrorIfNoOtherErrors(ErrorMessage) an error message to the Result.
- Recoverable user errors: Add a FeedbackHit explaining the condition and how to correct it.
fillDescription copied from class:
SearcherFill hit properties with data using the given summary class. Calling this on already filled results has no cost.
This needs to be overridden by federating searchers to contact search sources again by propagating the fill call down through the search chain, and by source searchers which talks to fill capable backends to request the data to be filled. Other searchers do not need to override this.
splitToGramsSplits the given item into n-grams and adds them as a CompositeItem containing WordItems searching the index of the input term. If the result is a single gram, that single WordItem is returned rather than the AndItem
term- the term to split, must be an item which implement the IndexedItem and BlockItem "mixins"
text- the text of the item, just stringValue() if the item is a TermItem
gramSize- the gram size to split to
query- the query in which this rewriting is done
- the root of the query subtree produced by this, containing the split items
protected final com.yahoo.language.process.GramSplitter getGramSplitter()Returns the (thread-safe) object to use to split the query text into grams.
protected CompositeItem createGramRoot(Query query)Creates the root of the query subtree which will contain the grams to match, called by
splitToGrams(com.yahoo.prelude.query.Item, java.lang.String, int, com.yahoo.search.Query). This hook is provided to make it easy to create a subclass which matches grams using a different composite item, e.g an OrItem.
This default implementation return new AndItem();
query- the input query, to make it possible to return a different composite item type depending on the query content
- the composite item to add the gram items to in
splitToGrams(com.yahoo.prelude.query.Item, java.lang.String, int, com.yahoo.search.Query)