sequencemanager.java

hsql是很有名的嵌入式数据库

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package org.hsqldb;

import org.hsqldb.HsqlNameManager.HsqlName;
import org.hsqldb.lib.HashMappedList;
import org.hsqldb.persist.Logger;

/**
 * Manages SEQUENCE objects for a Database instance. <p>
 *
 * @author fredt@users
 * @version 1.7.2
 * @since 1.7.2
 */
public class SequenceManager {

    HashMappedList sequenceMap;

    SequenceManager() {
        sequenceMap = new HashMappedList();
    }

    /**
     *  Drops a sequence with the specified name from this Database
     *
     * @param name of the sequence to drop
     * @throws HsqlException if a database access error occurs
     */
    void dropSequence(String name) throws HsqlException {

        boolean found = sequenceMap.containsKey(name);

        Trace.check(found, Trace.SEQUENCE_NOT_FOUND, name);
        sequenceMap.remove(name);
    }

    public NumberSequence getSequence(String name) {
        return (NumberSequence) sequenceMap.get(name);
    }

    NumberSequence createSequence(HsqlName hsqlname, long start,
                                  long increment,
                                  int type) throws HsqlException {

        Trace.check(!sequenceMap.containsKey(hsqlname.name),
                    Trace.SEQUENCE_ALREADY_EXISTS);

        NumberSequence sequence = new NumberSequence(hsqlname, start,
            increment, type);

        sequenceMap.put(hsqlname.name, sequence);

        return sequence;
    }

    String logSequences(Session c, Logger logger) throws HsqlException {

        for (int i = 0; i < sequenceMap.size(); i++) {
            NumberSequence seq = (NumberSequence) sequenceMap.get(i);

            if (seq.wasUsed()) {
                logger.writeSequenceStatement(c, seq);
                seq.resetWasUsed();
            }
        }

        return null;
    }
}