Inconsistent usage of ScriptScoreFunction in FiltersFunctionScoreQuery #3464
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ghost
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@brwe cool! thanks for recording those commit IDs |
brwe
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Aug 19, 2013
…Query This commit fixes inconsistencies in `function_score` and `filters_function_score` using scripts, see issue elastic#3464 The method 'ScoreFunction.factor(docId)' is removed completely, since the name suggests that this method actually computes a factor which was not the case. Multiplying the computed score is now handled by 'FiltersFunctionScoreQuery' and 'FunctionScoreQuery' and not implicitely performed in 'ScoreFunction.factor(docId, subQueryScore)' as was the case for 'BoostScoreFunction' and 'DecayScoreFunctions'. This commit also fixes the explain function for FiltersFunctionScoreQuery. Here, the influence of the maxBoost was never printed. Furthermore, the queryBoost was printed as beeing multiplied to the filter score. Closes elastic#3464
brwe
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Aug 23, 2013
…Query This commit fixes inconsistencies in `function_score` and `filters_function_score` using scripts, see issue #3464 The method 'ScoreFunction.factor(docId)' is removed completely, since the name suggests that this method actually computes a factor which was not the case. Multiplying the computed score is now handled by 'FiltersFunctionScoreQuery' and 'FunctionScoreQuery' and not implicitely performed in 'ScoreFunction.factor(docId, subQueryScore)' as was the case for 'BoostScoreFunction' and 'DecayScoreFunctions'. This commit also fixes the explain function for FiltersFunctionScoreQuery. Here, the influence of the maxBoost was never printed. Furthermore, the queryBoost was printed as beeing multiplied to the filter score. Closes #3464
mute
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Jul 29, 2015
…Query This commit fixes inconsistencies in `function_score` and `filters_function_score` using scripts, see issue elastic#3464 The method 'ScoreFunction.factor(docId)' is removed completely, since the name suggests that this method actually computes a factor which was not the case. Multiplying the computed score is now handled by 'FiltersFunctionScoreQuery' and 'FunctionScoreQuery' and not implicitely performed in 'ScoreFunction.factor(docId, subQueryScore)' as was the case for 'BoostScoreFunction' and 'DecayScoreFunctions'. This commit also fixes the explain function for FiltersFunctionScoreQuery. Here, the influence of the maxBoost was never printed. Furthermore, the queryBoost was printed as beeing multiplied to the filter score. Closes elastic#3464
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Scoring in
function_scoreandfilters_function_scorequeries is potentially inconsistent when using scripts.Brief overview of related classes
function_scoreandfilters_function_scoreallow a user to modify the score of a query (referred to as 'subQueryScore' from here on).In brief, there are two classes that compute scores based on a query and some function:
FunctionScoreQuery, which only has one function andFiltersFunctionScoreQuerywhich combines the result of several functions. For both classes, the function can be aScriptScoreFunction.ScoreFunction: Computes a score for a document. The two relevant methods are:score(docId, subQueryScore): computes a new score taking into account thesubQueryScoreand some other properties of a documents.factor(docId): computes a score solely based on properties of the document.FunctionScoreQuery.score()computes:score =
subQueryBoost*ScoreFunction.score(docId, subQueryScore)FiltersFunctionScoreQuery.CustomBoostFactorScorer.score()computes:score =
subQueryScore*subQueryBoost*combine(ScoreFunction1.factor(docId), ScoreFunction2.factor(docId),…)where combine can mean add, multiply, lowest value, etc.
The problem
ScoreFunctions.factor(docId)implies that the method computes a factor only and does not take into account thesubQueryScore. This is the way theScoreFunctionsare used inFiltersFunctionScoreQuery.CustomBoostFactorScorer: The methodfactor()is called for each score function and the result is than later multiplied to thesubQueryScore.However, the
ScriptScoreFunctionviolates this principle: scripts can use the_scorevariable which should be initialized with thesubQueryScorebefore the script is run, seeScriptScoreFunction.score(..). IfScriptScoreFunction.factor()is called, then the behavior is undefined, since the_scorevariable is either wrong or maybe even not initialized.This might cause unexpected behavior since this inconsistency is not transparent to the user.
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