org.exist.xquery
Interface Expression

All Known Subinterfaces:

Optimizable

All Known Implementing Classes:

AbstractExpression, AbstractMatchFunction, AtomicToString, Atomize, AttributeConstructor, BasicFunction, BinaryDoc, BinaryOp, BinaryToString, BindingExpression, BuiltinFunctions, CallFunction, CastableExpression, CastExpression, CatchFunction, CDATAConstructor, Clear, CollatingFunction, Collations, CollectionName, CombiningExpression, CommentConstructor, Compile, ConditionalExpression, CountInstances, Create, Delete, DescribeFunction, DocumentConstructor, DocumentNameOrId, DynamicAttributeConstructor, DynamicCardinalityCheck, DynamicCommentConstructor, DynamicNameCheck, DynamicPIConstructor, DynamicTextConstructor, DynamicTypeCheck, ElementConstructor, EnclosedExpr, EncodeURL, Eval, Except, ExclusiveLockFunction, ExtCollection, ExtDoctype, ExtDocument, ExtensionExpression, ExtFulltext, ExtNear, ExtPhrase, ExtRegexp, ExtRegexpOr, ExtXCollection, FileRead, FilteredExpression, FilterNested, ForExpr, FtIndexLookup, FunAbs, FunAdjustTimezone, FunAvg, FunBaseURI, FunBoolean, FunCeiling, FunCodepointEqual, FunCodepointsToString, FunCompare, FunConcat, FunContains, FunCount, Function, FunctionCall, FunctionFunction, FunCurrentDateTime, FunData, FunDateTime, FunDeepEqual, FunDefaultCollation, FunDistinctValues, FunDoc, FunDocAvailable, FunDoctype, FunDocumentURI, FunEmpty, FunEncodeForURI, FunEndsWith, FunError, FunEscapeHTMLURI, FunEscapeURI, FunExactlyOne, FunExists, FunFloor, FunGetDateComponent, FunGetDurationComponent, FunId, FunImplicitTimezone, FunIndexOf, FunInScopePrefixes, FunInsertBefore, FunIRIToURI, FunItemAt, FunLang, FunLast, FunLocalName, FunMatches, FunMax, FunMin, FunName, FunNamespaceURI, FunNamespaceURIForPrefix, FunNilled, FunNodeName, FunNormalizeSpace, FunNormalizeUnicode, FunNot, FunNumber, FunOneOrMore, FunPosition, FunQName, FunRemove, FunReplace, FunResolveQName, FunResolveURI, FunReverse, FunRoot, FunRound, FunRoundHalfToEven, FunStartsWith, FunString, FunStringJoin, FunStringPad, FunStringToCodepoints, FunStrLength, FunSubSequence, FunSubstring, FunSubstringAfter, FunSubstringBefore, FunSum, FunTokenize, FunTrace, FunTranslate, FunTrueOrFalse, FunUnEscapeURI, FunUnordered, FunUpperOrLowerCase, FunZeroOrOne, FuzzyIndexTerms, FuzzyMatchAll, FuzzyMatchAny, GeneralComparison, GetAttribute, GetAttributeNames, GetBuild, GetCookieNames, GetCookieValue, GetData, GetExistHome, GetHeader, GetHeaderNames, GetHostname, GetID, GetMemory, GetMethod, GetModuleLoadPath, GetNodeById, GetParameter, GetParameterNames, GetQueryString, GetRevision, GetServerName, GetServerPort, GetUploadedFile, GetUploadedFileName, GetURI, GetURL, GetVersion, GrammarTooling, HighlightMatches, IndexKeyDocuments, IndexKeyOccurrences, IndexKeys, IndexTerms, IndexType, Insert, InstanceOfExpression, InternalFunctionCall, Intersection, Invalidate, JavaCall, KWICDisplay, LetExpr, LiteralValue, LocationStep, LockFunction, LogFunction, LogicalOp, MatchCount, MatchRegexp, MD5, Modification, ModuleInfo, NamespaceConstructor, NGramSearch, NodeComparison, NodeConstructor, NodeId, OpAnd, OpNumeric, OpOr, PathExpr, PIConstructor, Predicate, Profile, PrologFunctions, QNameFunctions, QNameIndexLookup, QuantifiedExpression, RandomFunction, RangeExpression, RedirectTo, RegexpFilter, RemoveAttribute, Rename, Replace, RootNode, SequenceConstructor, Serialize, SetAttribute, SetCookie, SetCurrentUser, SetHeader, SharedLockFunction, Shutdown, SimpleStep, Step, StreamBinary, SystemProperty, SystemTime, TextConstructor, TextRank, Tokenize, Transform, TreatAsExpression, TriggerSystemTask, TypeswitchExpression, UnaryExpr, Union, UntypedValueCheck, Update, UserDefinedFunction, UUID, Validation, ValueComparison, VariableDeclaration, VariableReference, XMLDBAbstractCollectionManipulator, XMLDBAuthenticate, XMLDBChangeUser, XMLDBChmodCollection, XMLDBChmodResource, XMLDBCollection, XMLDBCollectionExists, XMLDBCopy, XMLDBCreateCollection, XMLDBCreated, XMLDBCreateUser, XMLDBDeleteUser, XMLDBGetChildCollections, XMLDBGetChildResources, XMLDBGetCurrentUser, XMLDBGetMimeType, XMLDBGetUserOrGroup, XMLDBHasLock, XMLDBIsAdmin, XMLDBLoadFromPattern, XMLDBMove, XMLDBPermissions, XMLDBPermissionsToString, XMLDBRegisterDatabase, XMLDBRemove, XMLDBRename, XMLDBSetCollectionPermissions, XMLDBSetResourcePermissions, XMLDBSize, XMLDBStore, XMLDBURIFunctions, XMLDBUserAccess, XMLDBXUpdate

public interface Expression

Base interface implemented by all classes which are part of an XQuery/XPath expression. The main method is eval(Sequence, Item). Please read the description there.

Field Summary

static int	DOT_TEST
static int	EXPRESSION_ID_INVALID Marks an invalid expression id.
static int	IGNORE_CONTEXT
static int	IN_PREDICATE Indicates that the expression is within a predicate or the where clause of a FLWOR.
static int	IN_UPDATE Indicates that the expression is used within an update statement.
static int	IN_WHERE_CLAUSE Indicates that the expression is within a where clause of a FLWOR.
static int	NEED_INDEX_INFO
static int	NO_CONTEXT_ID Indicates that no context id is supplied to an expression.
static int	SINGLE_STEP_EXECUTION Indicates that the query engine will call the expression once for every item in the context sequence.

Method Summary

void	accept(ExpressionVisitor visitor) Start traversing the expression tree using the specified ExpressionVisitor.
void	analyze(AnalyzeContextInfo contextInfo) Statically analyze the expression and its subexpressions.
void	dump(ExpressionDumper dumper) Write a diagnostic dump of the expression to the passed ExpressionDumper.
Sequence	eval(Sequence contextSequence) Evaluate the expression represented by this object.
Sequence	eval(Sequence contextSequence, Item contextItem) Evaluate the expression represented by this object.
XQueryAST	getASTNode() Returns the XQueryAST node from which this expression has been constructed by the parser.
int	getCardinality() The expected cardinality of the return value of the expression.
DocumentSet	getContextDocSet()
int	getContextId()
int	getDependencies() Returns a set of bit-flags, indicating some of the parameters on which this expression depends.
int	getExpressionId() Returns an id which uniquely identifies this expression within the compiled expression tree of the query.
void	resetState() Called to inform an expression that it should reset to its initial state.
int	returnsType() The static return type of the expression.
void	setASTNode(XQueryAST ast)
void	setContextDocSet(DocumentSet contextSet)
void	setPrimaryAxis(int axis)

Field Detail

SINGLE_STEP_EXECUTION

static final int SINGLE_STEP_EXECUTION

Indicates that the query engine will call the expression once for every item in the context sequence. This is what you would expect to be the normal behaviour of an XQuery processor. However, eXist tries to process some types of expressions in one single step for the whole input sequence. So if the flag is not set, the expression is only called once.

See Also:

Constant Field Values

IN_PREDICATE

static final int IN_PREDICATE

Indicates that the expression is within a predicate or the where clause of a FLWOR.

See Also:

Constant Field Values

IN_WHERE_CLAUSE

static final int IN_WHERE_CLAUSE

Indicates that the expression is within a where clause of a FLWOR. This flag will be set in addition to IN_PREDICATE.

See Also:

Constant Field Values

IN_UPDATE

static final int IN_UPDATE

Indicates that the expression is used within an update statement. Subexpressions should not cache any relevant data as it may be subject to change.

See Also:

Constant Field Values

NEED_INDEX_INFO

static final int NEED_INDEX_INFO

See Also:

Constant Field Values

DOT_TEST

static final int DOT_TEST

See Also:

Constant Field Values

NO_CONTEXT_ID

static final int NO_CONTEXT_ID

Indicates that no context id is supplied to an expression.

See Also:

Constant Field Values

IGNORE_CONTEXT

static final int IGNORE_CONTEXT

See Also:

Constant Field Values

EXPRESSION_ID_INVALID

static final int EXPRESSION_ID_INVALID

Marks an invalid expression id.

See Also:

Constant Field Values

Method Detail

getExpressionId

int getExpressionId()

Returns an id which uniquely identifies this expression within the compiled expression tree of the query.

Returns:

unique id or EXPRESSION_ID_INVALID

analyze

void analyze(AnalyzeContextInfo contextInfo)
             throws XPathException

Statically analyze the expression and its subexpressions. During the static analysis phase, the query engine can detect unknown variables and some type errors.

Throws:

XPathException

eval

Sequence eval(Sequence contextSequence,
              Item contextItem)
              throws XPathException

Evaluate the expression represented by this object. Depending on the context in which this expression is executed, either the context sequence, the context item or both of them may be set. An implementing class should know how to handle this. The general contract is as follows: if the Dependency.CONTEXT_ITEM bit is set in the bit field returned by getDependencies(), the eval method will be called once for every item in the context sequence. The contextItem parameter will be set to the current item. Otherwise, the eval method will only be called once for the whole context sequence and contextItem will be null. eXist tries to process the entire context set in one, single step whenever possible. Thus, most classes only expect context to contain a list of nodes which represents the current context of the expression. The position() function in XPath is an example for an expression, which requires both, context sequence and context item to be set. The context sequence might be a node set, a sequence of atomic values or a single node or atomic value.

Parameters:

contextSequence - the current context sequence.

contextItem - a single item, taken from context. This defines the item, the expression should work on.

Throws:

XPathException

eval

Sequence eval(Sequence contextSequence)
              throws XPathException

Evaluate the expression represented by this object. An overloaded method which just passes the context sequence depending on the expression context.

Throws:

XPathException

setPrimaryAxis

void setPrimaryAxis(int axis)

returnsType

int returnsType()

The static return type of the expression. This method should return one of the type constants defined in class Type. If the return type cannot be determined statically, return Type.ITEM.

getCardinality

int getCardinality()

The expected cardinality of the return value of the expression. Should return a bit mask with bits set as defined in class Cardinality.

getDependencies

int getDependencies()

Returns a set of bit-flags, indicating some of the parameters on which this expression depends. The flags are defined in Dependency.

Returns:

set of bit-flags

resetState

void resetState()

Called to inform an expression that it should reset to its initial state. All cached data in the expression object should be dropped. For example, the document() function calls this method whenever the input document set has changed.

accept

void accept(ExpressionVisitor visitor)

Start traversing the expression tree using the specified ExpressionVisitor.

Parameters:

visitor -

dump

void dump(ExpressionDumper dumper)

Write a diagnostic dump of the expression to the passed ExpressionDumper.

Parameters:

dumper - the expression dumper to write to

setContextDocSet

void setContextDocSet(DocumentSet contextSet)

getContextId

int getContextId()

getContextDocSet

DocumentSet getContextDocSet()

getASTNode

XQueryAST getASTNode()

Returns the XQueryAST node from which this expression has been constructed by the parser. This node contains location information (line number and column) important for error reports.

Returns:

XQueryAST node

setASTNode

void setASTNode(XQueryAST ast)