/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2010, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.dialect;

import java.sql.Types;

import org.hibernate.dialect.function.NoArgSQLFunction;
import org.hibernate.dialect.function.VarArgsSQLFunction;
import org.hibernate.type.StandardBasicTypes;

/**
 * A SQL dialect for Ingres 9.3 and later versions.
 * <p />
 * Changes:
 * <ul>
 * <li>Support for the SQL functions current_time, current_timestamp and current_date added</li>
 * <li>Type mapping of <code>Types.TIMESTAMP</code> changed from "timestamp with time zone" to "timestamp(9) with time zone"</li>
 * <li>Improved handling of "SELECT...FOR UPDATE" statements</li>
 * <li>Added support for pooled sequences</li>
 * <li>Added support for SELECT queries with limit and offset</li>
 * <li>Added getIdentitySelectString</li>
 * <li>Modified concatination operator</li>
 * </ul>
 * 
 * @author Enrico Schenk
 * @author Raymond Fan
 */
public class Ingres9Dialect extends IngresDialect {
    public Ingres9Dialect() {
        super();
        registerDateTimeFunctions();
        registerDateTimeColumnTypes();
        registerFunction( "concat", new VarArgsSQLFunction( StandardBasicTypes.STRING, "(", "||", ")" ) );
    }

	/**
	 * Register functions current_time, current_timestamp, current_date
	 */
	protected void registerDateTimeFunctions() {
		registerFunction("current_time", new NoArgSQLFunction("current_time", StandardBasicTypes.TIME, false));
		registerFunction("current_timestamp", new NoArgSQLFunction("current_timestamp", StandardBasicTypes.TIMESTAMP, false));
		registerFunction("current_date", new NoArgSQLFunction("current_date", StandardBasicTypes.DATE, false));
	}

	/**
	 * Register column types date, time, timestamp
	 */
	protected void registerDateTimeColumnTypes() {
		registerColumnType(Types.DATE, "ansidate");
		registerColumnType(Types.TIMESTAMP, "timestamp(9) with time zone");
	}

	// lock acquisition support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	/**
	 * Does this dialect support <tt>FOR UPDATE</tt> in conjunction with outer
	 * joined rows?
	 * 
	 * @return True if outer joined rows can be locked via <tt>FOR UPDATE</tt>.
	 */
	public boolean supportsOuterJoinForUpdate() {
		return false;
	}

	/**
	 * Is <tt>FOR UPDATE OF</tt> syntax supported?
	 * 
	 * @return True if the database supports <tt>FOR UPDATE OF</tt> syntax;
	 *         false otherwise.
	 */
	public boolean forUpdateOfColumns() {
		return true;
	}

	// SEQUENCE support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    /**
     * Get the select command used to retrieve the last generated sequence
     * value.
     *
     * @return Statement to retrieve last generated sequence value
     */
    public String getIdentitySelectString() {
         return "select last_identity()";
    }

	/**
	 * Get the select command used retrieve the names of all sequences.
	 * 
	 * @return The select command; or null if sequences are not supported.
	 * @see org.hibernate.tool.hbm2ddl.SchemaUpdate
	 */
	public String getQuerySequencesString() {
		return "select seq_name from iisequences";
	}

	/**
	 * Does this dialect support "pooled" sequences. Not aware of a better name
	 * for this. Essentially can we specify the initial and increment values?
	 * 
	 * @return True if such "pooled" sequences are supported; false otherwise.
	 * @see #getCreateSequenceStrings(String, int, int)
	 * @see #getCreateSequenceString(String, int, int)
	 */
	public boolean supportsPooledSequences() {
		return true;
	}

	// current timestamp support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	/**
	 * Should the value returned by {@link #getCurrentTimestampSelectString} be
	 * treated as callable. Typically this indicates that JDBC escape sytnax is
	 * being used...
	 * 
	 * @return True if the {@link #getCurrentTimestampSelectString} return is
	 *         callable; false otherwise.
	 */
	public boolean isCurrentTimestampSelectStringCallable() {
		return false;
	}

	/**
	 * Does this dialect support a way to retrieve the database's current
	 * timestamp value?
	 * 
	 * @return True if the current timestamp can be retrieved; false otherwise.
	 */
	public boolean supportsCurrentTimestampSelection() {
		return true;
	}

	/**
	 * Retrieve the command used to retrieve the current timestammp from the
	 * database.
	 * 
	 * @return The command.
	 */
	public String getCurrentTimestampSelectString() {
		return "select current_timestamp";
	}

	/**
	 * Expression for current_timestamp
	 */
	public String getCurrentTimestampSQLFunctionName() {
		return "current_timestamp";
	}

	// union subclass support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	/**
	 * Does this dialect support UNION ALL, which is generally a faster variant
	 * of UNION?
	 * 
	 * @return True if UNION ALL is supported; false otherwise.
	 */
	public boolean supportsUnionAll() {
		return true;
	}

	// Informational metadata ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	/**
	 * For the underlying database, is READ_COMMITTED isolation implemented by
	 * forcing readers to wait for write locks to be released?
	 * 
	 * @return true
	 */
	public boolean doesReadCommittedCauseWritersToBlockReaders() {
		return true;
	}

	/**
	 * For the underlying database, is REPEATABLE_READ isolation implemented by
	 * forcing writers to wait for read locks to be released?
	 * 
	 * @return true
	 */
	public boolean doesRepeatableReadCauseReadersToBlockWriters() {
		return true;
	}

	// limit/offset support ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

	/**
	 * Does this dialect's LIMIT support (if any) additionally support
	 * specifying an offset?
	 * 
	 * @return true
	 */
	public boolean supportsLimitOffset() {
		return true;
	}

	/**
	 * Does this dialect support bind variables (i.e., prepared statememnt
	 * parameters) for its limit/offset?
	 * 
	 * @return false
	 */
	public boolean supportsVariableLimit() {
		return false;
	}

	/**
	 * Does the <tt>LIMIT</tt> clause take a "maximum" row number instead
	 * of a total number of returned rows?
	 */
	public boolean useMaxForLimit() {
		return false;
	}

	/**
	 * Add a <tt>LIMIT</tt> clause to the given SQL <tt>SELECT</tt>
	 * 
	 * @return the modified SQL
	 */
	public String getLimitString(String querySelect, int offset, int limit) {
        StringBuffer soff = new StringBuffer(" offset " + offset);
        StringBuffer slim = new StringBuffer(" fetch first " + limit + " rows only");
		StringBuffer sb = new StringBuffer(querySelect.length() +
            soff.length() + slim.length()).append(querySelect);
		if (offset > 0) {
			sb.append(soff);
		}
        if (limit > 0) {
            sb.append(slim);
        }
		return sb.toString();
	}
}
