Package org.basex.query.expr

Class Preds

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.expr.Arr

org.basex.query.expr.Preds

Direct Known Subclasses:

Filter, Step

public abstract class Preds
extends Arr

Abstract predicate expression, implemented by Filter and Step.

Author:

BaseX Team 2005-22, BSD License, Christian Gruen

Field Summary

Fields inherited from class org.basex.query.expr.Arr

exprs

Fields inherited from class org.basex.query.expr.ParseExpr

exprType, info

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Preds(InputInfo info, SeqType seqType, Expr... preds)	Constructor.

Method Summary

Modifier and Type	Method	Description
Expr	compile(CompileContext cc)	Compiles and optimizes the expression, assigns types and cardinalities.
Expr	flattenEbv(Expr root, boolean ebv, CompileContext cc)	Flattens predicates for boolean evaluation.
boolean	inlineable(InlineContext ic)	Checks if inlining is possible.
protected boolean	match(Item item, QueryContext qc)	Checks if the specified item matches the predicates.
boolean	mayBePositional()	Checks if at least one of the predicates may be positional.
protected static boolean	numeric(Expr expr)	Checks if the specified expression returns an empty sequence or a deterministic numeric value.
protected boolean	simplify(CompileContext cc, Expr root)	Simplifies all predicates.
void	toString(QueryString qs)	Creates a query string.
protected abstract Expr	type(Expr expr)	Assigns the expression type.

Methods inherited from class org.basex.query.expr.Arr

accept, allAreValues, args, checkUp, copyAll, count, equals, exprSize, flatten, has, inline, mayBePositional, removeEmpty, simplifyAll, toXml

Methods inherited from class org.basex.query.expr.ParseExpr

adoptType, atomValue, checkAllUp, checkNoEmpty, checkNoEmpty, checkNoneUp, checkNoUp, checkType, checkType, checkUp, copyType, ctxValue, data, ebv, info, item, iter, refineType, seqType, size, test, toArray, toArray, toAtomItem, toB64, toB64, toBin, toBin, toBoolean, toBoolean, toBytes, toBytes, toDouble, toDouble, toElem, toFloat, toFunction, toItem, toItem, toLong, toLong, toMap, toMap, toNode, toNode, toNodeOrNull, toNumber, toNumberOrNull, toQNm, toQNm, toString, toString, toStringOrNull, toToken, toToken, toTokenOrNull, toZeroToken, value

Methods inherited from class org.basex.query.expr.Expr

arg, atomItem, atomIter, copy, ddo, funcType, hasFreeVars, indexAccessible, isSimple, markTailCalls, mergeEbv, optimize, optimizePos, simplify, simplifyFor, typeCheck, uses, vacuous, visitAll

Methods inherited from class org.basex.query.expr.ExprInfo

description, toErrorString, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Preds

protected Preds(InputInfo info,
                SeqType seqType,
                Expr... preds)

Constructor.

Parameters:

info - input info

seqType - sequence type

preds - predicates

Method Detail

compile

public Expr compile(CompileContext cc)
             throws QueryException

Description copied from class: Expr

Compiles and optimizes the expression, assigns types and cardinalities.

Overrides:

compile in class Arr

Parameters:

cc - compilation context

Returns:

optimized expression

Throws:

QueryException - query exception

type

protected abstract Expr type(Expr expr)

Assigns the expression type.

Parameters:

expr - root expression (can be null)

Returns:

actual root expression (can be null)

match

protected final boolean match(Item item,
                              QueryContext qc)
                       throws QueryException

Checks if the specified item matches the predicates.

Parameters:

item - item to be checked

qc - query context

Returns:

result of check

Throws:

QueryException - query exception

simplify

protected final boolean simplify(CompileContext cc,
                                 Expr root)
                          throws QueryException

Simplifies all predicates.

Parameters:

cc - compilation context

root - root expression

Returns:

true if evaluation can be skipped

Throws:

QueryException - query exception

flattenEbv

public final Expr flattenEbv(Expr root,
                             boolean ebv,
                             CompileContext cc)
                      throws QueryException

Flattens predicates for boolean evaluation. Drops solitary context values, flattens nested predicates.

Parameters:

root - root expression

ebv - EBV check

cc - compilation context

Returns:

optimized or original expression

Throws:

QueryException - query exception

numeric

protected static boolean numeric(Expr expr)

Checks if the specified expression returns an empty sequence or a deterministic numeric value.

Parameters:

expr - expression

Returns:

result of check

mayBePositional

public boolean mayBePositional()

Checks if at least one of the predicates may be positional.

Returns:

result of check

inlineable

public boolean inlineable(InlineContext ic)

Description copied from class: Expr

Checks if inlining is possible. This function is called by InlineContext.inlineable(org.basex.query.expr.Expr...) and: CNode.inlineable(org.basex.query.InlineContext) returns false if the new expression construct new nodes. The following tests might reject inlining if the expression is a context reference:

• inlineable(org.basex.query.InlineContext)
• Path.inlineable(org.basex.query.InlineContext)
• SimpleMap.inlineable(org.basex.query.InlineContext)
• StaticJavaCall.inlineable(org.basex.query.InlineContext)
• TransformWith.inlineable(org.basex.query.InlineContext)

Overrides:

inlineable in class Arr

Parameters:

ic - inlining context

Returns:

result of check

toString

public void toString(QueryString qs)

Description copied from class: ExprInfo

Creates a query string.

Specified by:

toString in class ExprInfo

Parameters:

qs - query string builder