Quadcap Embeddable Database

com/quadcap/sql/Constraint.java

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package com.quadcap.sql;

/* Copyright 1999 - 2003 Quadcap Software.  All rights reserved.
 *
 * This software is distributed under the Quadcap Free Software License.
 * This software may be used or modified for any purpose, personal or
 * commercial.  Open Source redistributions are permitted.  Commercial
 * redistribution of larger works derived from, or works which bundle
 * this software requires a "Commercial Redistribution License"; see
 * http://www.quadcap.com/purchase.
 *
 * Redistributions qualify as "Open Source" under  one of the following terms:
 *   
 *    Redistributions are made at no charge beyond the reasonable cost of
 *    materials and delivery.
 *
 *    Redistributions are accompanied by a copy of the Source Code or by an
 *    irrevocable offer to provide a copy of the Source Code for up to three
 *    years at the cost of materials and delivery.  Such redistributions
 *    must allow further use, modification, and redistribution of the Source
 *    Code under substantially the same terms as this license.
 *
 * Redistributions of source code must retain the copyright notices as they
 * appear in each source code file, these license terms, and the
 * disclaimer/limitation of liability set forth as paragraph 6 below.
 *
 * Redistributions in binary form must reproduce this Copyright Notice,
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 * forth as paragraph 6 below, in the documentation and/or other materials
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 *
 * The Software is provided on an "AS IS" basis.  No warranty is
 * provided that the Software is free of defects, or fit for a
 * particular purpose.  
 *
 * Limitation of Liability. Quadcap Software shall not be liable
 * for any damages suffered by the Licensee or any third party resulting
 * from use of the Software.
 */

import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;

import java.util.Vector;

import java.sql.SQLException;

import com.quadcap.sql.index.Btree;

import com.quadcap.util.Debug;

/**
 * A constraint is a condition which must be satisfied relative to
 * the rows of a table.  Constraint checking hooks are available for
 * both before and after table-modifying operations.
 *
 * @author Stan Bailes
 */
public abstract class Constraint implements Externalizable {
    transient Table             table;
    transient int[]             columns;
    Vector                      colNames        = new Vector();
    String                      name            = null;
    int                         spec            = 0;

    // bits 0..1 of the constraint
    public static final int     FULL            = (1 << 0);
    public static final int     PARTIAL         = (1 << 1);

    // two actions bits for update and delete
    public static final int     NOACTION        = 0;
    public static final int     CASCADE         = 1;
    public static final int     SETNULL         = 2;
    public static final int     SETDEFAULT      = 3;

    // bits 2..3 (action)
    public static final int     UPDATE          = 2;
    // bits 4..5 (action)
    public static final int     DELETE          = 4;

    // bit 6
    public static final int     DEFERRABLE      = (1 << 6);
    // bit 7
    public static final int     INIT_DEFERRED   = (1 << 7);
    // bit 8
    public static final int     GLOBAL          = (1 << 8);

    /**
     * Default constructor
     */
    public Constraint() {}

    /**
     * Construct a named constraint
     */
    public Constraint(String name) {
        this.name = name;
    }

    /**
     * Construct a named constraint with a list of columns
     */
    public Constraint(String name, Vector colNames) {
        this.name = name;
        this.colNames = colNames;
    }

    /**
     * Return the constraint's name
     */
    public String getName() {
        return name;
    }

    /**
     * Set the constraint's name
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * Get the referential action for the specified operation (UPD OR DEL)
     */
    public int getRefAction(int opType) {
        return (spec >> opType) & 0x3;
    }

    /**
     * String names for Various referential actions
     */
    static String[] refActions = { "NO ACTION", "CASCADE", "SET NULL",
                                   "SET DEFAULT" };

    /**
     * Return the referential action for the specified operation
     */
    public String getRefActionString(int opType) {
        return refActions[getRefAction(opType)];
    }

    /**
     * Set the 'global' flag
     */
    public void setGlobal(boolean g) {
        if (g) {
            spec |= GLOBAL;
        } else {
            spec &= ~GLOBAL;
        }
    }

    /**
     * Get the 'global' flag
     */
    public boolean isGlobal() { return (spec & GLOBAL) != 0; }

    /**---INSERT
     * Called before a row is INSERTED, with an opportunity to signal
     * a constraint violation if one can be detected.
     */
    abstract public void checkInsert(Session session, Row row)
        throws SQLException, IOException
    ;

    /**
     * Called after the specified row has been inserted, with the resulting
     * row ID, and with the active index.  Constraints which maintain state
     * (such as an index) would extend this class and implement this
     * method to update the index
     */
    abstract public void applyInsert(Session session, Row row, long rowId,
                                     Constraint activeIndex)
        throws SQLException, IOException
    ;

    /**----DELETE
     * Called before a row is DELETED, with an opportunity to signal a
     * constraint violation if one can be detected.
     */
    abstract public void checkDelete(Session session, Row row, long rowId)
        throws SQLException, IOException
    ;

    /**
     * Called after a row has been deleted, with the old row and row ID.
     * Constraints which maintain state (such as an index) would extend
     * this class and implement this method to update the index.
     */
    abstract public void applyDelete(Session session, Row row, long rowId,
                                     Constraint activeIndex)
        throws SQLException, IOException
    ;

    /**----UPDATE
     * Called before a row is UPDATED, with an opportunity to signal a
     * constraint violation if one can be detected.
     *
     * Because the oldRow may be 'lazy', it's important to instantiate
     * whatever items are going to be needed later by applyUpdate *now*,
     * otherwise, apply may get the 'new' versions of those items, because
     * the underlying byte stream is modified by the time applyUpdate
     * gets called.
     */
    abstract public void checkUpdate(Session session, byte[] oldKey, Row row,
                                     Row oldRow, long rowId,
                                     Constraint activeIndex)
        throws SQLException, IOException
    ;

    /**
     * Called after a row has been updated, with the old row, old key,
     * new row and row ID. 
     * Constraints which maintain state (such as an index) would extend
     * this class and implement this method to update the index.
     */
    abstract public void applyUpdate(Session session, byte[] oldKey, Row row,
                                     Row oldRow, long rowId,
                                     Constraint activeIndex)
        throws SQLException, IOException
    ;

    /**
     * Called when the constraint itself is being removed.  Constraints which
     * allocate resources of any kind should release them here since they
     * are about to be discarded and gc'ed.
     */
    abstract public void delete(Session session)
        throws SQLException, IOException
    ;

    /**
     * Called when the constraint is added.  Constraints which maintain
     * state (e.g., indexes) can build their initial data structures (or
     * whatever it is that they do at this time)
     */
    abstract public void add(Session session)
        throws SQLException, IOException;

    /**
     * Called to undo a constraint-add operation.
     */
    public void undoAdd(Session session)
        throws SQLException, IOException {
        delete(session);
    }


    /**
     * Called to undo a constraint-add operation.
     */
    public void undoDelete(Session session)
        throws SQLException, IOException
    {
        add(session);
    }


    /**
     * Set the deferrable flags
     */
    public void setDeferrable(int def) {
        this.spec |= def;
    }
    
    /**
     * Set the referential integrity flags
     */
    public void setRefSpec(int ref) {
        this.spec |= ref;
    }

    /**
     * Set the contstraint's table
     */
    public void setTable(Table table) throws SQLException {
        this.table = table;
        this.columns = null;
        getColumns();
    }

    /**
     * Get the constraint's table
     */
    public Table getTable() { return this.table; }

    /**
     * Return the referential integrity and deferrability flags
     */
    public int getSpec() {
        return spec;
    }

    /**
     * Convenience method for setting single column constraints.
     */
    public void setColumn(Column column) {
        if (colNames.size() != 0) {
            colNames = new Vector();
        }
        colNames.add(column.getName());
        this.columns = null;
    }

    /**
     * For the simple, single column constraint, the constraint's column
     *
     * @exception SQLException if called for a multi-column constraint.
     */
    public Column getColumn() throws SQLException {
        getColumns();
        if (columns.length < 1) throw new SQLException("No column", "Q0000");
        if (columns.length > 1)
            throw new SQLException("Not a single column constraint: " + this,
                                   "Q0000");
        return table.getColumn(columns[0]);
    }

    /**
     * Return the number of columns described by the constraint.
     */
    public int getColumnCount() {
        return colNames.size();
    }

    /**
     * Zero based!!!!
     */
    public Column getColumn(int c) throws SQLException {
        return table.getColumn(columns[c]);
    }

    /**
     * Read me from a stream
     */
    public void readExternal(ObjectInput in)
        throws IOException, ClassNotFoundException
    {
        spec = in.readInt();
        name = (String)in.readObject();
        colNames = (Vector)in.readObject();
        columns = null;
    }

    /**
     * Write me to a stream
     */
    public void writeExternal(ObjectOutput out) throws IOException {
        out.writeInt(spec);
        out.writeObject(name);
        out.writeObject(colNames);
    }

    /**
     * Return the integer indexes in the table's column list of the
     * columns in this constraint.  We return a copy of our internal
     * array, for speed, and trust the caller to not mess with the
     * array...
     */
    public  int[] getColumns() throws SQLException {
        if (columns == null) {
            columns = table.mapColumns(colNames);
        }
        return columns;
    }

    /**
     * Reset any mapped columns (e.g. in case a column is added or deleted)
     */
    public void resetColumns() throws SQLException {
        columns = null;
    }
    
    /**
     * Return a vector containing all of the column names
     */
    public Vector getColumnNames() throws SQLException {
        return colNames;
    }

    /**
     * Funny, but a lot of constraints have indexes.  For the ones that
     * do, this can be a nifty little function.
     */
    public Btree getIndex(Database db) throws IOException {
        return null;
    }

    /**
     * Higher priority (larger numbers) execute first.
     */
    public int getPriority() { return 3; }

    /**
     * Is this constraint 'deferred'?
     */
    public boolean isDeferred() {
        return false;   // only foreign key constraints are deferrable...
    }

    /**
     * Return a displayable representation for debugging
     */
    public String toString() {
        StringBuffer sb = new StringBuffer("Constraint ");
        sb.append(name);
        sb.append(": ");
        if (table == null) {
            sb.append("<null table>");
        } else {
            sb.append(table.getName());
        }
        sb.append("(");
        if (colNames != null) {
            for (int i = 0; i < colNames.size(); i++) {
                if (i > 0) sb.append(',');
                sb.append(colNames.elementAt(i).toString());
            }
        }
        sb.append(")");
        if ((spec & FULL) != 0) sb.append(" FULL");
        if ((spec & PARTIAL) != 0) sb.append(" PARTIAL");

        if (getRefAction(UPDATE) != NOACTION) {
            sb.append(" ON UPDATE ");
            sb.append(getRefActionString(UPDATE));
        }
        if (getRefAction(DELETE) != NOACTION) {
            sb.append(" ON DELETE ");
            sb.append(getRefActionString(DELETE));
        }
        if ((spec & DEFERRABLE) != 0) sb.append(" DEFERRABLE");
        if ((spec & INIT_DEFERRED) != 0) sb.append(" INITIALLY DEFERRED");
        
        return sb.toString();
    }
}