The
ExtendableQueryParser enables arbitrary query parser extension based on a customizable field naming scheme. The lucene query syntax allows implicit and explicit field definitions as query prefix followed by a colon (':') character. The
ExtendableQueryParser allows to encode extension keys into the field symbol associated with a registered instance of
ParserExtension. A customizable separation character separates the extension key from the actual field symbol. The
ExtendableQueryParser splits (
Extensions.SplitExtensionField(string, string)) the extension key from the field symbol and tries to resolve the associated
ParserExtension. If the parser can't resolve the key or the field token does not contain a separation character,
ExtendableQueryParser yields the same behavior as its super class
QueryParser. Otherwise, if the key is associated with a
ParserExtension instance, the parser builds an instance of
ExtensionQuery to be processed by
ParserExtension.Parse(ExtensionQuery).If a extension field does not contain a field part the default field for the query will be used.
To guarantee that an extension field is processed with its associated extension, the extension query part must escape any special characters like '*' or '['. If the extension query contains any whitespace characters, the extension query part must be enclosed in quotes. Example ('_' used as separation character):
title_customExt:"Apache Lucene\?" OR content_customExt:prefix\*
Search on the default field:
_customExt:"Apache Lucene\?" OR _customExt:prefix\*
The ExtendableQueryParser itself does not implement the logic how field and extension key are separated or ordered. All logic regarding the extension key and field symbol parsing is located in Extensions. Customized extension schemes should be implemented by sub-classing Extensions.
For details about the default encoding scheme see Extensions.
Extensions ParserExtension ExtensionQuery 