indexupdateplanner.java

用java语言简单实现数据库的初步功能

package simpledb.index.planner;

import static simpledb.index.metadata.IndexInfo.*;

import java.util.Iterator;
import java.util.Map;

import simpledb.record.RID;
import simpledb.server.SimpleDB;
import simpledb.tx.Transaction;
import simpledb.index.Index;
import simpledb.index.metadata.IndexInfo;
import simpledb.parse.*;
import simpledb.planner.*;
import simpledb.query.*;

/**
 * A modification of the basic update planner.
 * It dispatches each update statement to the corresponding
 * index planner.
 * It also now understands the "create index" statement.
 * @author Edward Sciore
 */
public class IndexUpdatePlanner implements UpdatePlanner {
	
	public int executeInsert(InsertData data, Transaction tx) {
		Plan plan = new TablePlan(data.tableName(), tx);

		// first, insert the record
		UpdateScan s = (UpdateScan) plan.open();
		s.insert();
		RID rid = s.getRid();

		// then modify each field, inserting an index record if appropriate
		Map<String,IndexInfo> indexes = SimpleDB.mdMgr().getIndexInfo(data.tableName(), tx);
		Iterator<Constant> valIter = data.vals().iterator();
		for (String fldname : data.fields()) {
			Constant val = valIter.next();
			s.setVal(fldname, val);

			IndexInfo ii = indexes.get(fldname);
			if (ii != null) {
				Index idx = ii.open();
 				idx.insert(val, rid);
				idx.close();
			}
		}
		s.close();
		return 1;
	}
	
	public int executeDelete(DeleteData data, Transaction tx) {
		String tblname = data.tableName();
		Plan p = new TablePlan(tblname, tx);
		p = new SelectPlan(p, data.pred());
		Map<String,IndexInfo> indexes = SimpleDB.mdMgr().getIndexInfo(tblname, tx);

		UpdateScan s = (UpdateScan) p.open();
		int count = 0;
		while(s.next()) {
			// first, delete the record's RID from every index
			RID rid = s.getRid();
			for (String fldname : indexes.keySet()) {
				Constant val = s.getVal(fldname);
				Index idx = indexes.get(fldname).open();
				idx.delete(val, rid);
				idx.close();
			}
			// then delete the record
			s.delete();
			count++;
		}
		s.close();
		return count;
	}

	public int executeModify(ModifyData data, Transaction tx) {
		String tblname = data.tableName();
		String fldname = data.targetField();
		Plan p = new TablePlan(tblname, tx);
		p = new SelectPlan(p, data.pred());

		IndexInfo ii = SimpleDB.mdMgr().getIndexInfo(tblname, tx).get(fldname);
		Index idx = (ii == null) ? null : ii.open();

		UpdateScan s = (UpdateScan) p.open();
		int count = 0;
		while(s.next()) {
			// first, update the record
			Constant newval = data.newValue().evaluate(s);
			Constant oldval = s.getVal(fldname);
			s.setVal(data.targetField(), newval);

			// then update the appropriate index, if it exists
			if (idx != null) {
				RID rid = s.getRid();
				idx.delete(oldval, rid);
				idx.insert(newval, rid);
			}
			count++;
		}
		if (idx != null) idx.close();
		s.close();
		return count;
	}
	
	public int executeCreateTable(CreateTableData data, Transaction tx) {
		SimpleDB.mdMgr().createTable(data.tableName(), data.newSchema(), tx);
		return 0;
	}

	public int executeCreateView(CreateViewData data, Transaction tx) {
		SimpleDB.mdMgr().createView(data.viewName(), data.viewDef(), tx);
		return 0;
	}
	
	public int executeCreateIndex(CreateIndexData data, Transaction tx) {
		SimpleDB.mdMgr().createIndex(data.tableName(), data.fieldName(), BTREE, tx);
		return 0;
	}
}