root / trunk / libraries / libGDBMS / src / main / java / com / hardcode / gdbms / engine / instruction / Field.java @ 10627
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package com.hardcode.gdbms.engine.instruction; |
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import com.hardcode.gdbms.driver.exceptions.ReadDriverException; |
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import com.hardcode.gdbms.engine.data.DataSource; |
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import com.hardcode.gdbms.engine.values.Value; |
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/**
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* Clase que representa un campo en un DataSource. La clase por s? sola no
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* identifica al campo, ya que la tabla a la que pertenece el campo viene
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* definida por un ?ndice entero. Esto se debe a que para definir un campo es
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* necesario tambi?n un array de tablas sobre las que se aplica dicho ?ndice.
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*
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* @author Fernando Gonz?lez Cort?s
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*/
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public class Field extends AbstractExpression implements Expression { |
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private DataSource[] tables; |
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private int dataSourceIndex; |
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private int fieldId; |
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private DataSource dataSource; |
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/**
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* Indice de la tabla donde se encuentra el campo al que este objeto hace
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* referencia
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*
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* @return
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*/
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public int getDataSourceIndex() { |
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return dataSourceIndex;
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} |
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/**
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* Identificador del campo al que este objeto hace referencia
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*
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* @return
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*/
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public int getFieldId() { |
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return fieldId;
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} |
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/**
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* Establece el ?ndice dentr de un array de tablas del campo al que este
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* objeto hace referencia
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*
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* @param source
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*/
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public void setDataSourceIndex(int source) { |
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dataSourceIndex = source; |
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} |
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/**
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* Establece el identificador al que este objeto hace referencia
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*
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* @param i
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*/
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public void setFieldId(int i) { |
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fieldId = i; |
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} |
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/**
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* Obtiene la colecci?n de tablas sobre las que los ?ndices dataSourceIndex
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* y fieldId son v?lidos
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*
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* @return
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*/
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public DataSource[] getTables() { |
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return tables;
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} |
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/**
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* Establece la colecci?n de tablas sobre las que se definen los ?ndices
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* dataSourceIndex y fieldId
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*
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* @param sources
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*/
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public void setTables(DataSource[] sources) { |
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tables = sources; |
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} |
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/**
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* Devuelve el ?ndice que ocupa el campo en la colecci?n de los campos de
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* todas las tablas del array tables.
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*
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* @return ?ndice absoluto del campo
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* @throws ReadDriverException TODO
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*/
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public int getAbsoluteIndex() throws ReadDriverException { |
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int acum = 0; |
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for (int table = 0; table < dataSourceIndex; table++) { |
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acum += tables[table].getFieldCount(); |
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} |
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acum += fieldId; |
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return acum;
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} |
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/**
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* @see com.hardcode.gdbms.engine.instruction.Expression#evaluate(long)
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*/
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public Value evaluate(long row) throws EvaluationException { |
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try {
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return dataSource.getFieldValue(row, getAbsoluteIndex());
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} catch (ReadDriverException e) {
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throw new EvaluationException(); |
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} |
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} |
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/**
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* Obtiene la fuente de datos sobre la que obtiene su valor este campo en
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* su m?todo evaluate
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*
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* @return
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*/
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public DataSource getDataSource() { |
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return dataSource;
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} |
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/**
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* Establece la fuente de datos sobre la que obtiene su valor este campo en
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* su m?todo evaluate
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*
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* @param source
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*/
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public void setDataSource(DataSource source) { |
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dataSource = source; |
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} |
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/**
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* @see com.hardcode.gdbms.engine.instruction.Expression#getFieldName()
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*/
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public String getFieldName() { |
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return null; |
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} |
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/**
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* @see com.hardcode.gdbms.engine.instruction.Expression#isLiteral()
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*/
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public boolean isLiteral() { |
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return false; |
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} |
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/**
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* @see com.hardcode.gdbms.engine.instruction.Expression#simplify()
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*/
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public void simplify() { |
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} |
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/**
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* @see com.hardcode.gdbms.engine.instruction.Expression#calculateLiteralCondition()
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*/
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public void calculateLiteralCondition() { |
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} |
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} |