tablefilter.java

非常棒的java数据库

/*
 * Copyright 2004-2008 H2 Group. Licensed under the H2 License, Version 1.0
 * (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.table;

import java.sql.SQLException;

import org.h2.command.Parser;
import org.h2.command.dml.Select;
import org.h2.constant.SysProperties;
import org.h2.engine.Right;
import org.h2.engine.Session;
import org.h2.expression.ConditionAndOr;
import org.h2.expression.Expression;
import org.h2.index.Cursor;
import org.h2.index.Index;
import org.h2.index.IndexCondition;
import org.h2.message.Message;
import org.h2.result.Row;
import org.h2.result.SearchRow;
import org.h2.result.SortOrder;
import org.h2.util.ObjectArray;
import org.h2.util.StringUtils;
import org.h2.value.Value;

/**
 * A table filter represents a table that is used in a query. There is one such
 * object whenever a table (or view) is used in a query. For example the
 * following query has 2 table filters: SELECT * FROM TEST T1, TEST T2.
 */
public class TableFilter implements ColumnResolver {
    private static final int BEFORE_FIRST = 0, FOUND = 1, AFTER_LAST = 2, NULL_ROW = 3;
    private final Table table;
    private final Select select;
    private String alias;
    private Session session;
    private Index index;
    private IndexColumn[] indexColumns;
    private Cursor cursor;
    private int scanCount;
    private boolean used; // used in the plan

    // conditions that can be used for direct index lookup (start or end)
    private final ObjectArray indexConditions = new ObjectArray();

    // conditions that can't be used for index lookup, 
    // but for row filter for this table (ID=ID, NAME LIKE '%X%')
    private Expression filterCondition;

    // the complete join condition
    private Expression joinCondition;
    private SearchRow currentSearchRow;
    private Row current;
    private int state;

    private TableFilter join;

    private boolean outerJoin;
    private boolean foundOne;
    private Expression fullCondition;

    public TableFilter(Session session, Table table, String alias, boolean rightsChecked, Select select)
            throws SQLException {
        this.session = session;
        this.table = table;
        this.alias = alias;
        this.select = select;
        if (!rightsChecked) {
            session.getUser().checkRight(table, Right.SELECT);
        }
    }

    public Select getSelect() {
        return select;
    }

    public Table getTable() {
        return table;
    }

    public void lock(Session session, boolean exclusive, boolean force) throws SQLException {
        table.lock(session, exclusive, force);
        if (join != null) {
            join.lock(session, exclusive, force);
        }
    }

    public PlanItem getBestPlanItem(Session session) throws SQLException {
        PlanItem item;
        if (indexConditions.size() == 0) {
            item = new PlanItem();
            item.setIndex(table.getScanIndex(session));
            item.cost = item.getIndex().getCost(session, null);
        } else {
            int len = table.getColumns().length;
            int[] masks = new int[len];
            for (int i = 0; i < indexConditions.size(); i++) {
                IndexCondition condition = (IndexCondition) indexConditions.get(i);
                if (condition.isEvaluatable()) {
                    if (condition.isAlwaysFalse()) {
                        masks = null;
                        break;
                    } else {
                        int id = condition.getColumn().getColumnId();
                        masks[id] |= condition.getMask();
                    }
                }
            }
            item = table.getBestPlanItem(session, masks);
        }
        if (join != null) {
            setEvaluatable(join);
            item.setJoinPlan(join.getBestPlanItem(session));
            // TODO optimizer: calculate cost of a join: should use separate
            // expected row number and lookup cost
            item.cost += item.cost * item.getJoinPlan().cost;
        }
        return item;
    }

    private void setEvaluatable(TableFilter join) {
        // this table filter is now evaluatable - in all sub-joins
        do {
            Expression e = join.getJoinCondition();
            if (e != null) {
                e.setEvaluatable(this, true);
            }
            join = join.getJoin();
        } while (join != null);
    }

    public void setPlanItem(PlanItem item) {
        setIndex(item.getIndex());
        if (join != null) {
            if (item.getJoinPlan() != null) {
                join.setPlanItem(item.getJoinPlan());
            }
        }
    }

    public void prepare() throws SQLException {
        // forget all unused index conditions
        for (int i = 0; i < indexConditions.size(); i++) {
            IndexCondition condition = (IndexCondition) indexConditions.get(i);
            if (!condition.isAlwaysFalse()) {
                Column col = condition.getColumn();
                if (index.getColumnIndex(col) < 0) {
                    indexConditions.remove(i);
                    i--;
                }
            }
        }
        if (join != null) {
            if (SysProperties.CHECK && join == this) {
                throw Message.getInternalError("self join");
            }
            join.prepare();
        }
        if (filterCondition != null) {
            filterCondition = filterCondition.optimize(session);
        }
        if (joinCondition != null) {
            joinCondition = joinCondition.optimize(session);
        }
    }

    public void startQuery(Session session) throws SQLException {
        this.session = session;
        scanCount = 0;
        if (join != null) {
            join.startQuery(session);
        }
    }

    public void reset() {
        if (join != null) {
            join.reset();
        }
        state = BEFORE_FIRST;
        foundOne = false;
    }

    public boolean next() throws SQLException {
        boolean alwaysFalse = false;
        if (state == AFTER_LAST) {
            return false;
        } else if (state == BEFORE_FIRST) {
            SearchRow start = null, end = null;
            for (int i = 0; i < indexConditions.size(); i++) {
                IndexCondition condition = (IndexCondition) indexConditions.get(i);
                if (condition.isAlwaysFalse()) {
                    alwaysFalse = true;
                    break;
                }
                Column column = condition.getColumn();
                int type = column.getType();
                int id = column.getColumnId();
                Value v = condition.getCurrentValue(session).convertTo(type);
                boolean isStart = condition.isStart(), isEnd = condition.isEnd();
                IndexColumn idxCol = indexColumns[id];
                if (idxCol != null && (idxCol.sortType & SortOrder.DESCENDING) != 0) {
                    // if the index column is sorted the other way, we swap end and start
                    // NULLS_FIRST / NULLS_LAST is not a problem, as nulls never match anyway
                    boolean temp = isStart;
                    isStart = isEnd;
                    isEnd = temp;
                }
                if (isStart) {
                    // TODO index: start.setExpression(id, bigger(start.getValue(id), e));
                    if (start == null) {
                        start = table.getTemplateRow();
                    }
                    start.setValue(id, v);
                }
                if (isEnd) {
                    // TODO index: end.setExpression(id, smaller(end.getExpression(id), e));
                    if (end == null) {
                        end = table.getTemplateRow();
                    }
                    end.setValue(id, v);
                }
            }
            if (!alwaysFalse) {
                cursor = index.find(session, start, end);
                if (join != null) {
                    join.reset();
                }
            }
        } else {
            // state == FOUND || LAST_ROW
            // the last row was ok - try next row of the join
            if (join != null && join.next()) {
                return true;
            }
        }
        while (true) {
            // go to the next row
            if (state == NULL_ROW) {
                break;
            }
            if (alwaysFalse) {
                state = AFTER_LAST;
            } else {
                if ((++scanCount & 4095) == 0) {
                    checkTimeout();
                }
                if (cursor.next()) {
                    currentSearchRow = cursor.getSearchRow();
                    current = null;
                    // cursor.get();
                    state = FOUND;
                } else {
                    state = AFTER_LAST;
                }
            }
            // if no more rows found, try the null row (for outer joins only)
            if (state == AFTER_LAST) {
                if (outerJoin && !foundOne) {
                    state = NULL_ROW;
                    current = table.getNullRow();
                    currentSearchRow = current;
                } else {
                    break;
                }
            }
            if (!isOk(filterCondition)) {
                continue;
            }
            boolean joinConditionOk = isOk(joinCondition);
            if (state == FOUND) {
                if (joinConditionOk) {
                    foundOne = true;
                } else {
                    continue;
                }
            }
            if (join != null) {
                join.reset();
                if (!join.next()) {
                    continue;
                }