org.basex.query.expr

Class CmpG

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.Cmp

org.basex.query.expr.CmpG

Direct Known Subclasses:

CmpHashG, CmpSimpleG

public class CmpG
extends Cmp

General comparison.

Author:

BaseX Team 2005-21, BSD License, Christian Gruen

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CmpG.OpG Comparators.

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

Constructor and Description
CmpG(Expr expr1, Expr expr2, CmpG.OpG op, Collation coll, StaticContext sc, InputInfo info) Constructor.

Method Summary

Modifier and Type	Method and Description
CmpG	copy(CompileContext cc, IntObjMap<Var> vm) Copies an expression.
String	description() Returns a string description of the expression.
boolean	equals(Object obj) This function is e.g.
boolean	indexAccessible(IndexInfo ii) Checks if an expression can be rewritten to an index access.
CmpG	invert() If possible, returns an expression with inverted operands.
Bln	item(QueryContext qc, InputInfo ii) Evaluates the expression and returns the resulting item, or Empty.VALUE if the expression yields an empty sequence.
Expr	mergeEbv(Expr expr, boolean or, CompileContext cc) Tries to merge two expressions that are part of an EBV test.
Expr	optimize(CompileContext cc) Optimizes an already compiled expression without recompiling its sub-expressions.
CmpV.OpV	opV() Returns the value operator of the expression.
void	plan(QueryPlan plan) Creates a query plan.
void	plan(QueryString qs) Creates a query string.

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

invert, optPred

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

accept, allAreValues, args, checkUp, compile, copyAll, count, exprSize, flatten, has, inline, inline, inlineable, mayBePositional, simplifyAll

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

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

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

arg, atomItem, atomIter, data, data, ddo, funcType, hasFreeVars, isSimple, markTailCalls, simplifyFor, typeCheck, uses, vacuous, visitAll

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

toErrorString, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

CmpG

public CmpG(Expr expr1,
            Expr expr2,
            CmpG.OpG op,
            Collation coll,
            StaticContext sc,
            InputInfo info)

Constructor.

Parameters:

expr1 - first expression

expr2 - second expression

op - operator

coll - collation (can be null)

sc - static context

info - input info

Method Detail

optimize

public final Expr optimize(CompileContext cc)
                    throws QueryException

Description copied from class: Expr

Optimizes an already compiled expression without recompiling its sub-expressions.

Overrides:

optimize in class Expr

Parameters:

cc - compilation context

Returns:

optimized expression

Throws:

QueryException - query exception

item

public Bln item(QueryContext qc,
                InputInfo ii)
         throws QueryException

Description copied from class: Expr

Evaluates the expression and returns the resulting item, or Empty.VALUE if the expression yields an empty sequence. If this method is not implemented, Expr.value(QueryContext) must be implemented instead.

Overrides:

item in class ParseExpr

Parameters:

qc - query context

ii - input info (only required by Seq instances, which have no input info)

Returns:

item or Empty.VALUE

Throws:

QueryException - query exception

invert

public final CmpG invert()

Description copied from class: Cmp

If possible, returns an expression with inverted operands.

Specified by:

invert in class Cmp

Returns:

original or null

opV

public final CmpV.OpV opV()

Description copied from class: Cmp

Returns the value operator of the expression.

Specified by:

opV in class Cmp

Returns:

operator, or null for node comparisons

mergeEbv

public Expr mergeEbv(Expr expr,
                     boolean or,
                     CompileContext cc)
              throws QueryException

Description copied from class: Expr

Tries to merge two expressions that are part of an EBV test. Called by And, Or), Step and Filter. Overwritten by CmpG, CmpIR, CmpR, CmpSR, ItrPos, Pos and others.

Overrides:

mergeEbv in class Expr

Parameters:

expr - second expression

or - union or intersection

cc - compilation context

Returns:

optimized expression or null

Throws:

QueryException - query exception

indexAccessible

public final boolean indexAccessible(IndexInfo ii)
                              throws QueryException

Description copied from class: Expr

Checks if an expression can be rewritten to an index access. If so, the index expression will be bound to IndexInfo.expr. This method will be called by the Path expression.

Overrides:

indexAccessible in class Expr

Parameters:

ii - index info

Returns:

true if an index can be used

Throws:

QueryException - query exception

copy

public CmpG copy(CompileContext cc,
                 IntObjMap<Var> vm)

Description copied from class: Expr

Copies an expression. Used for inlining functions, or for copying static queries. It is utilized by VarRef.inline(org.basex.query.InlineContext), FuncItem.inline(org.basex.query.expr.Expr[], org.basex.query.CompileContext), Closure.inline(org.basex.query.InlineContext) and StaticFunc.inline(org.basex.query.expr.Expr[], org.basex.query.CompileContext).

Specified by:

copy in class Expr

Parameters:

cc - compilation context

vm - mapping from old variable IDs to new variable copies. Required by Closure.copy(org.basex.query.CompileContext, org.basex.util.hash.IntObjMap<org.basex.query.var.Var>) and VarRef.copy(org.basex.query.CompileContext, org.basex.util.hash.IntObjMap<org.basex.query.var.Var>)

Returns:

copied expression

equals

public final boolean equals(Object obj)

Description copied from class: Arr

This function is e.g. called by:

• If.optimize(CompileContext), Switch.optimize(CompileContext), Typeswitch.optimize(CompileContext), in order to discard identical expressions.
• CmpR.mergeEbv(Expr, boolean, CompileContext) or CmpSR.mergeEbv(Expr, boolean, CompileContext), in order to merge expressions with identical input.
• optimize(CompileContext) or CmpV.optimize(CompileContext), in order to pre-evaluate equality tests.
• optimize(CompileContext) or Pos.get(Expr, CmpV.OpV, InputInfo, CompileContext), in order to compare the start and end value.
• PathCache, in order to find identical root values at runtime.

Must be overwritten by implementing class.

Overrides:

equals in class Arr

description

public String description()

Description copied from class: ExprInfo

Returns a string description of the expression. This method is only called by error messages. Contrary to the ExprInfo.toString() method, arguments are not included in the output.

Overrides:

description in class ExprInfo

Returns:

result of check

plan

public final void plan(QueryPlan plan)

Description copied from class: ExprInfo

Creates a query plan.

Overrides:

plan in class Arr

Parameters:

plan - expression plan

plan

public final void plan(QueryString qs)

Description copied from class: ExprInfo

Creates a query string.

Specified by:

plan in class ExprInfo

Parameters:

qs - query string builder