tableworks.java

一个用java写的开源的数据库系统

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package org.hsqldb;

import java.sql.SQLException;
import java.util.Vector;
import java.util.Hashtable;

// fredt@users 20020520 - patch 1.7.0 - ALTER TABLE support
// tony_lai@users 20020820 - patch 595172 by tlai@users - drop constraint fix

/**
 * The methods in this class perform alterations to the structure of an
 * existing table which may result in a new Table object
 *
 * @version 1.7.0
 */
class TableWorks {

    private Table table;

    TableWorks(Table table) {
        this.table = table;
    }

    Table getTable() {
        return table;
    }

// fredt@users 20020225 - patch 1.7.0 - require existing index for foreign key

    /**
     *  Creates a foreign key according to current sql.strict_fk or
     *  sql.strong_fk settings. Foreign keys are enforced via indexes on both
     *  the referencing (child) and referenced (parent) tables.
     *  <p>
     *  If sql.strict_fk is set (default for new databases) a pre-existing
     *  primary key or unique index is required on the referenced columns
     *  of the referenced table.
     *  <p>
     *  When there is no primary key or unique index, a new index is created
     *  automatically. If sql.strong_fk is set in the abasence of
     *  sql.strict_fk, this automatic index will be a unique index. Otherwise
     *  (for compatibility with existing data created with HSQLDB 1.61 or
     *  earlier) it will be an ordinary index.
     *
     *  The non-unique index on the referencing table is created if none
     *  exits. The existence of a PK or unique constraint is required for
     *  backward referencing foreign keys. This is becuase the index must
     *  always be created before the foreign key DDL is processed.
     *  Any index, including a user-defined one can be used for forward
     *  referencing FK's.
     *
     *  Foriegn keys on temp tables can reference other temp tables with the
     *  same rules above. When they reference other permanent tables, the
     *  sql.strict_fk is always applied. Foreign keys on permanent tables
     *  cannot reference temp tables.
     *
     *  Currently, duplicate foreign keys can be declared, but they do not
     *  create any additional indexes. (fred@users)
     *
     * @param  fkcol
     * @param  expcol
     * @param  fkname           foreign key name
     * @param  expTable
     * @param  cascade        foreign key enforces cascading deletes
     * @throws SQLException
     */
    void createForeignKey(int fkcol[], int expcol[], HsqlName fkname,
                          Table expTable,
                          boolean cascade) throws SQLException {

        if (table.getConstraint(fkname.name) != null) {
            throw Trace.error(Trace.CONSTRAINT_ALREADY_EXISTS);
        }

        int interval = table.dDatabase.getTableIndex(table)
                       - table.dDatabase.getTableIndex(expTable);
        Index exportindex = (interval == 0)
                            ? expTable.getConstraintIndexForColumns(expcol,
                                true)
                            : expTable.getIndexForColumns(expcol, true);
        boolean strict =
            table.dDatabase.getProperties().isPropertyTrue("sql.strict_fk");

        strict = strict || (!expTable.isTemp() && table.isTemp());

        if (expTable.isTemp() &&!table.isTemp()) {
            throw Trace.error(Trace.FOREIGN_KEY_NOT_ALLOWED,
                              "referenced table cannot be TEMPORARY");
        }

        if (strict && (exportindex == null ||!exportindex.isUnique())) {
            throw Trace.error(Trace.INDEX_NOT_FOUND,
                              "needs unique index on referenced columns of "
                              + expTable.getName().statementName);
        }

        Index fkindex = (interval >= 0)
                        ? table.getConstraintIndexForColumns(fkcol, false)
                        : table.getIndexForColumns(fkcol, false);

        if (fkindex == null) {
            HsqlName iname = HsqlName.makeAutoName("IDX");

            fkindex = createIndex(fkcol, iname, false);
        }

        boolean strong =
            table.dDatabase.getProperties().isPropertyTrue("sql.strong_fk");

        if (exportindex == null || (strong &&!exportindex.isUnique())) {
            HsqlName   iname = HsqlName.makeAutoName("FK");
            TableWorks tw    = new TableWorks(expTable);

            exportindex = tw.createIndex(expcol, iname, strong);
            expTable    = tw.getTable();
        }

        HsqlName pkname = HsqlName.makeAutoName("REF", fkname.name);
        Constraint c = new Constraint(pkname, fkname, expTable, table,
                                      expcol, fkcol, exportindex, fkindex,
                                      cascade);

        table.addConstraint(c);
        expTable.addConstraint(new Constraint(pkname, c));
    }

// fredt@users 20020315 - patch 1.7.0 - create index bug
// this method would break existing foreign keys as the table order in the DB
// was changed. Instead, we now link in place of the old table

    /**
     *  Because of the way indexes and column data are held in memory and
     *  on disk, it is necessary to recreate the table when an index is added
     *  to a non-empty table. (fredt@users)
     *