tablefilter.java

一个可以在applet窗体上持行sql语句并显示返回结果的程序

/*
 * TableFilter.java
 */

package org.hsql;
import java.sql.*;
import java.util.Vector;

class TableFilter {
  private Table tTable;
  private String sAlias;
  private Index iIndex;
  private Node nCurrent;
  private Object oEmptyData[];
  private Expression eStart,eEnd;
  private Expression eAnd;
  private boolean bOuterJoin;

  // this is public to improve performance
  Object oCurrentData[];

  // Object[] getCurrent() {
  //   return oCurrentData;
  // }
  TableFilter(Table t,String alias,boolean outerjoin) {
    tTable=t;
    iIndex=null;
    sAlias=alias!=null ? alias : t.getName();
    bOuterJoin=outerjoin;
    oEmptyData=tTable.getNewRow();
  }
  String getName() {
    return sAlias;
  }
  Table getTable() {
    return tTable;
  }
  void setCondition(Expression e) throws SQLException {
    int type=e.getType();
    Expression e1=e.getArg();
    Expression e2=e.getArg2();
    if(type==Expression.AND) {
      setCondition(e1);
      setCondition(e2);
      return;
    }
    int candidate;
    switch(type) {
    case Expression.NOT_EQUAL:
    case Expression.LIKE:  // todo: maybe use index
    case Expression.IN:
      candidate=0;
      break;
    case Expression.EQUAL:
      candidate=1;
      break;
    case Expression.BIGGER:
    case Expression.BIGGER_EQUAL:
      candidate=2;
      break;
    case Expression.SMALLER:
    case Expression.SMALLER_EQUAL:
      candidate=3;
      break;
    default:
      // not a condition so forget it
      return;
    }
    if(e1.getFilter()==this) {
      // ok include this
    } else if(e2.getFilter()==this && candidate!=0) {
      // swap and try again to allow index usage
      e.swapCondition();
      setCondition(e);
      return;
    } else {
      // unrelated: don't include
      return;
    }
    Trace.assert(e1.getFilter()==this,"setCondition");
    if(!e2.isResolved()) {
      return;
    }
    if(candidate==0) {
      addAndCondition(e);
      return;
    }
    int i=e1.getColumnNr();
    Index index=tTable.getIndexForColumn(i);
    if(index==null || (iIndex!=index && iIndex!=null)) {
      // no index or already another index is used
      addAndCondition(e);
      return;
    }
    iIndex=index;
    if(candidate==1) {
      // candidate for both start & end
      if(eStart!=null || eEnd!=null) {
        addAndCondition(e);
        return;
      }
      eStart=new Expression(e);
      eEnd=eStart;
    } else if(candidate==2) {
      // candidate for start
      if(eStart!=null) {
        addAndCondition(e);
        return;
      }
      eStart=new Expression(e);
    } else if(candidate==3) {
      // candidate for end
      if(eEnd!=null) {
        addAndCondition(e);
        return;
      }
      eEnd=new Expression(e);
    }
    e.setTrue();
  }
  boolean findFirst() throws SQLException {
    if(iIndex==null) {
      iIndex=tTable.getPrimaryIndex();
    }
    if(eStart==null) {
      nCurrent=iIndex.first();
    } else {
      int type=eStart.getArg().getDataType();
      Object o=eStart.getArg2().getValue(type);
      nCurrent=iIndex.findFirst(o,eStart.getType());
    }
    while(nCurrent!=null) {
      oCurrentData=nCurrent.getData();
      if(!test(eEnd)) {
        break;
      }
      if(test(eAnd)) {
        return true;
      }
      nCurrent=iIndex.next(nCurrent);
    }
    oCurrentData=oEmptyData;
    if(bOuterJoin) {
      return true;
    }
    return false;
  }
  boolean next() throws SQLException {
    if(bOuterJoin && nCurrent==null) {
      return false;
    }
    nCurrent=iIndex.next(nCurrent);
    while(nCurrent!=null) {
      oCurrentData=nCurrent.getData();
      if(!test(eEnd)) {
        break;
      }
      if(test(eAnd)) {
        return true;
      }
      nCurrent=iIndex.next(nCurrent);
    }
    oCurrentData=oEmptyData;
    return false;
  }

  private void addAndCondition(Expression e) {
    Expression e2=new Expression(e);
    if(eAnd==null) {
      eAnd=e2;
    } else {
      Expression and=new Expression(Expression.AND,eAnd,e2);
      eAnd=and;
    }
    e.setTrue();
  }
  private boolean test(Expression e) throws SQLException {
    if(e==null) {
      return true;
    }
    return e.test();
  }
}