[英]What does cause Antlr to create a large tokenstream resulting in out of memory
我們的Web應用程序之一經常死於內存不足。 我們從內存轉儲中收集的稀疏數據表明我們的antlr解析實現中存在問題。 我們看到的是一個antlr令牌流,其中包含超過一百萬個項目。 尚未找到導致此問題的輸入文本。
這可能與零寬度項目beeing匹配有關嗎? 語法中是否可能會導致內存使用過多的另一個問題?
這是我們當前使用的語法:
grammar AdvancedQueries;
options {
language = Java;
output = AST;
ASTLabelType=CommonTree;
}
tokens {
FOR;
END;
FIELDSEARCH;
TARGETFIELD;
RELATION;
NOTNODE;
ANDNODE;
NEARDISTANCE;
OUTOFPLACE;
}
@header {
package de.bsmo.fast.parsing;
}
@lexer::header {
package de.bsmo.fast.parsing;
}
startExpression : orEx;
expressionLevel4
: LPARENTHESIS! orEx RPARENTHESIS! | atomicExpression | outofplace;
expressionLevel3
: (fieldExpression) | expressionLevel4 ;
expressionLevel2
: (nearExpression) | expressionLevel3 ;
expressionLevel1
: (countExpression) | expressionLevel2 ;
notEx : NOT^? a=expressionLevel1 ;
andEx : (notEx -> notEx)
(AND? a=notEx -> ^(ANDNODE $andEx $a))*;
orEx : andEx (OR^ andEx)*;
countExpression : COUNT LPARENTHESIS countSub RPARENTHESIS RELATION NUMBERS -> ^(COUNT countSub RELATION NUMBERS);
countSub
: orEx;
nearExpression : NEAR LPARENTHESIS (WORD|PHRASE) MULTIPLESEPERATOR (WORD|PHRASE) MULTIPLESEPERATOR NUMBERS RPARENTHESIS -> ^(NEAR WORD* PHRASE* ^(NEARDISTANCE NUMBERS));
fieldExpression : WORD PROPERTYSEPERATOR fieldSub -> ^(FIELDSEARCH ^(TARGETFIELD WORD) fieldSub );
fieldSub
: WORD | PHRASE | LPARENTHESIS! orEx RPARENTHESIS!;
atomicExpression
: WORD
| PHRASE
| NUMBERS
;
//Out of place are elements captured that may be in the parseable input but need to be ommited from output later
//Those unwanted elements are captured here.
//MULTIPLESEPERATOR capture unwanted ","
outofplace
: MULTIPLESEPERATOR -> ^(OUTOFPLACE ^(MULTIPLESEPERATOR));
fragment NUMBER : ('0'..'9');
fragment CHARACTER : ('a'..'z'|'A'..'Z'|'0'..'9'|'*'|'?');
fragment QUOTE : ('"');
fragment LESSTHEN : '<';
fragment MORETHEN: '>';
fragment EQUAL: '=';
fragment SPACE : ('\u0009'|'\u0020'|'\u000C'|'\u00A0');
fragment WORDMATTER: ('!'|'0'..'9'|'\u0023'..'\u0027'|'*'|'+'|'\u002D'..'\u0039'|'\u003F'..'\u007E'|'\u00A1'..'\uFFFE');
LPARENTHESIS : '(';
RPARENTHESIS : ')';
AND : ('A'|'a')('N'|'n')('D'|'d');
OR : ('O'|'o')('R'|'r');
ANDNOT : ('A'|'a')('N'|'n')('D'|'d')('N'|'n')('O'|'o')('T'|'t');
NOT : ('N'|'n')('O'|'o')('T'|'t');
COUNT:('C'|'c')('O'|'o')('U'|'u')('N'|'n')('T'|'t');
NEAR:('N'|'n')('E'|'e')('A'|'a')('R'|'r');
PROPERTYSEPERATOR : ':';
MULTIPLESEPERATOR : ',';
WS : (SPACE) { $channel=HIDDEN; };
NUMBERS : (NUMBER)+;
RELATION : (LESSTHEN | MORETHEN)? EQUAL // '<=', '>=', or '='
| (LESSTHEN | MORETHEN); // '<' or '>'
PHRASE : (QUOTE)(.)*(QUOTE);
WORD : WORDMATTER* ;
造成這種情況的最常見原因是令牌的長度可以為0。在文件中的任何其他兩個令牌之間可以有無數個這樣的令牌。 現在,定義這樣的令牌會在ANTLR 4中導致編譯器警告。
以下規則可以匹配空字符串:
WORD : WORDMATTER*;
也許您打算使用以下內容代替?
WORD : WORDMATTER+;
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