[richfaces-issues] [JBoss JIRA] Created: (RF-8262) Unnecessary filtering of fields in a Richfaces DataTable

[Sebastian Rueber (JIRA)]

Unnecessary filtering of fields in a Richfaces DataTable
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                 Key: RF-8262
                 URL: https://jira.jboss.org/jira/browse/RF-8262
             Project: RichFaces
          Issue Type: Patch
      Security Level: Public (Everyone can see)
          Components: component, component-ScrollableDataTable, component-tables
            Reporter: Sebastian Rueber



This patch is a solution for the DataTable problem, when using the internal filter.

e.g.:
<rich:dataTable value="${bean.listDataModel}" var="row">
  <rich:column filterBy="row.name" />

reason for this problem is the class org.richfaces.model.ModifiableModel with its method filter(...)

the method filter(...) always calculates the filterBy value for all cells and rows in the table, which has the 
filter expression.

example:
500 rows and 7 columns leads to 3500 calculations. it depends on how complex the expressions are, but it
may take a while.

in some cases the expressions are calculated unnecessary.

example 1: empty filter fields
if the user has not entered any filter expressions in fields with a filter attribute, for example if the table is rendered initialy.
calculated expressions 3500
needed expressions 0

example 2: shortcut evaluation
the filter fields are linked by an AND logical operator. that means, if you have 7 fields and the first does not match,
the remaining 6 field should not be evaluated.
calculated expressions 3500
needed expressions 3500 - x

in our application we are using our own table model, but i would like to contribute some code, which may give you
an idea, how to fix this quickly.

solution code for filter method

@Override
protected List<Object> filter(List<FilterField> aFilterFields) {
  List<Object> filteredCollection = new ArrayList<Object>();
  ExpressionFactory tempFactory = new ExpressionFactory(FacesContext.getCurrentInstance(), var, aFilterFields);

  for (Object temp : rowKeys) {
    Integer tempKey = (Integer) temp;
    Sample tempSample = data.get(tempKey);

    if (accept(tempSample, aFilterFields, tempFactory)) {
      filteredCollection.add(tempKey);
    }
  }
  rowKeys = filteredCollection;
  return rowKeys;
}

public boolean accept(Sample aSample, List<FilterField> aFilterList, ExpressionFactory aFactory) {
  for (FilterField filterField : aFilterList) {
    if (filterField instanceof ExtendedFilterField) {
      String filterValue = ((ExtendedFilterField) filterField).getFilterValue();
      if (filterValue != null) {
        filterValue = filterValue.trim().toUpperCase(locale);
        if (filterValue.length() > 0) {
          // delayed until here, were it is really needed
          Object property = aFactory.eval(filterField.getExpression(), aSample);
          if (property == null || !property.toString().trim().toUpperCase(locale).startsWith(filterValue)) {
            return false;
          }
        }
      }
    } else {
      Object property = aFactory.eval(filterField.getExpression(), aSample);
      if (!((Boolean) property).booleanValue()) {
        return false;
      }
    }
  }
  return true;
}


solution code for the ExpressionFactory



package org.richfaces.model.impl.expressive;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import javax.el.ELContext;
import javax.el.ELResolver;
import javax.el.MethodExpression;
import javax.el.ValueExpression;
import javax.faces.application.Application;
import javax.faces.component.UIViewRoot;
import javax.faces.context.FacesContext;

import org.richfaces.model.Field;

public class ExpressionFactory {

  private Map<javax.el.Expression, Expression> expressionMap;

  public ExpressionFactory(FacesContext context, final String var, List<? extends Field> sortOrder) {

    Application application = context.getApplication();
    ELResolver resolver = application.getELResolver();
    ELContext elContext = context.getELContext();

    expressionMap = new HashMap<javax.el.Expression, Expression>();

    for (Field field : sortOrder) {
      javax.el.Expression elExpression = field.getExpression();
      Expression expression;

      if (elExpression instanceof ValueExpression) {
        ValueExpression valueExpression = (ValueExpression) elExpression;

        if (valueExpression.isLiteralText()) {
          String expressionString = valueExpression.getExpressionString();

          if (expressionString.startsWith(UIViewRoot.UNIQUE_ID_PREFIX)) {
            expression = new NullExpression(expressionString);
          } else {
            expression = new SimplePropertyExpression(expressionString, elContext, resolver);
          }
        } else {
          expression = new ValueBindingExpression(context, valueExpression, var);
        }
      } else if (elExpression instanceof MethodExpression) {
        expression = new MethodBindingExpression(context, (MethodExpression) elExpression);
      } else {
        throw new IllegalArgumentException();
      }

      expressionMap.put(elExpression, expression);
    }
  }

  public Object eval(javax.el.Expression anExpression, Object anObject) {
    return expressionMap.get(anExpression).evaluate(anObject);
  }
}




 


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