Namespace List
Here is a list of all documented namespaces with brief descriptions:

Xapian | The Xapian namespace contains public interfaces for the Xapian library
Auto | Database factory functions which determine the database type automatically
Chert | Database factory functions for the chert backend
InMemory | Database factory functions for the inmemory backend
Remote | Database factory functions for the remote backend
Unicode | Functions associated with handling Unicode characters
AssertionError | AssertionError is thrown if a logical assertion inside Xapian fails
BB2Weight | This class implements the BB2 weighting scheme
BM25PlusWeight | Xapian::Weight subclass implementing the BM25+ probabilistic formula
BM25Weight | Xapian::Weight subclass implementing the BM25 probabilistic formula
BoolWeight | Class implementing a "boolean" weighting scheme
Compactor | Compact a database, or merge and compact several
CoordWeight | Xapian::Weight subclass implementing Coordinate Matching
Database | This class is used to access a database, or a group of databases
DatabaseClosedError | Indicates an attempt to access a closed database
DatabaseCorruptError | DatabaseCorruptError indicates database corruption was detected
DatabaseCreateError | DatabaseCreateError indicates a failure to create a database
DatabaseError | DatabaseError indicates some sort of database related error
DatabaseLockError | DatabaseLockError indicates failure to lock a database
DatabaseModifiedError | DatabaseModifiedError indicates a database was modified
DatabaseNotFoundError | Indicates an attempt to access a database not present
DatabaseOpeningError | DatabaseOpeningError indicates failure to open a database
DatabaseVersionError | DatabaseVersionError indicates that a database is in an unsupported format
DateRangeProcessor | Handle a date range
DateValueRangeProcessor | Handle a date range
DecreasingValueWeightPostingSource | Read weights from a value which is known to decrease as docid increases
DLHWeight | This class implements the DLH weighting scheme, which is a representative scheme of the Divergence from Randomness Framework by Gianni Amati
DocNotFoundError | Indicates an attempt to access a document not present in the database
Document | A handle representing a document in a Xapian database
DPHWeight | This class implements the DPH weighting scheme
Enquire | This class provides an interface to the information retrieval system for the purpose of searching
Error | All exceptions thrown by Xapian are subclasses of Xapian::Error
ErrorHandler | Decide if a Xapian::Error exception should be ignored
ESet | Class representing a list of search results
ESetIterator | Iterator over a Xapian::ESet
ExpandDecider | Virtual base class for expand decider functor
ExpandDeciderAnd | ExpandDecider subclass which rejects terms using two ExpandDeciders
ExpandDeciderFilterPrefix | ExpandDecider subclass which restrict terms to a particular prefix
ExpandDeciderFilterTerms | ExpandDecider subclass which rejects terms in a specified list
FeatureUnavailableError | Indicates an attempt to use a feature which is unavailable
FieldProcessor | Base class for field processors
FixedWeightPostingSource | A posting source which returns a fixed weight for all documents
GreatCircleMetric | Calculate the great-circle distance between two coordinates on a sphere
IfB2Weight | This class implements the IfB2 weighting scheme
IneB2Weight | This class implements the IneB2 weighting scheme
InL2Weight | This class implements the InL2 weighting scheme
InternalError | InternalError indicates a runtime problem of some sort
InvalidArgumentError | InvalidArgumentError indicates an invalid parameter value was passed to the API
InvalidOperationError | InvalidOperationError indicates the API was used in an invalid way
KeyMaker | Virtual base class for key making functors
LatLongCoord | A latitude-longitude coordinate
LatLongCoords | A sequence of latitude-longitude coordinates
LatLongCoordsIterator | An iterator across the values in a LatLongCoords object
LatLongDistanceKeyMaker | KeyMaker subclass which sorts by distance from a latitude/longitude
LatLongDistancePostingSource | Posting source which returns a weight based on geospatial distance
LatLongMetric | Base class for calculating distances between two lat/long coordinates
LMWeight | Xapian::Weight subclass implementing the Language Model formula
LogicError | The base class for exceptions indicating errors in the program logic
MatchDecider | Base class for matcher decision functor
MatchSpy | Abstract base class for match spies
MSet | Class representing a list of search results
MSetIterator | Iterator over a Xapian::MSet
MultiValueKeyMaker | KeyMaker subclass which combines several values
NetworkError | Indicates a problem communicating with a remote database
NetworkTimeoutError | Indicates a timeout expired while communicating with a remote database
NumberRangeProcessor | Handle a number range
NumberValueRangeProcessor | Handle a number range
PL2PlusWeight | Xapian::Weight subclass implementing the PL2+ probabilistic formula
PL2Weight | This class implements the PL2 weighting scheme
PositionIterator | Class for iterating over term positions
PostingIterator | Class for iterating over a list of terms
PostingSource | Base class which provides an "external" source of postings
Query | Class representing a query
QueryParser | Build a Xapian::Query object from a user query string
QueryParserError | Indicates a query string can't be parsed
RangeError | RangeError indicates an attempt to access outside the bounds of a container
RangeProcessor | Base class for range processors
Registry | Registry for user subclasses
RSet | A relevance set (R-Set)
RuntimeError | The base class for exceptions indicating errors only detectable at runtime
SerialisationError | Indicates an error in the std::string serialisation of an object
SimpleStopper | Simple implementation of Stopper class - this will suit most users
Stem | Class representing a stemming algorithm
StemImplementation | Class representing a stemming algorithm implementation
Stopper | Abstract base class for stop-word decision functor
StringValueRangeProcessor | Handle a string range
TermGenerator | Parses a piece of text and generate terms
TermIterator | Class for iterating over a list of terms
TfIdfWeight | Xapian::Weight subclass implementing the tf-idf weighting scheme
TradWeight | Xapian::Weight subclass implementing the traditional probabilistic formula
UnimplementedError | UnimplementedError indicates an attempt to use an unimplemented feature
Utf8Iterator | An iterator which returns Unicode character values from a UTF-8 encoded string
ValueCountMatchSpy | Class for counting the frequencies of values in the matching documents
ValueIterator | Class for iterating over document values
ValueMapPostingSource | A posting source which looks up weights in a map using values as the key
ValuePostingSource | A posting source which generates weights from a value slot
ValueRangeProcessor | Base class for value range processors
ValueSetMatchDecider | MatchDecider filtering results based on whether document values are in a user-defined set
ValueWeightPostingSource | A posting source which reads weights from a value slot
Weight | Abstract base class for weighting schemes
WildcardError | WildcardError indicates an error expanding a wildcarded query
WritableDatabase | This class provides read/write access to a database