UpdateStatement.java

/**********************************************************************
Copyright (c) 2015 Andy Jefferson and others. All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

Contributors:
     ...
 **********************************************************************/
package org.datanucleus.store.rdbms.sql;

import java.util.Iterator;
import java.util.Map;

import org.datanucleus.store.rdbms.RDBMSStoreManager;
import org.datanucleus.store.rdbms.identifier.DatastoreIdentifier;
import org.datanucleus.store.rdbms.sql.expression.BooleanExpression;
import org.datanucleus.store.rdbms.sql.expression.BooleanSubqueryExpression;
import org.datanucleus.store.rdbms.sql.expression.SQLExpression;
import org.datanucleus.store.rdbms.table.Table;

/**
 * SQL UPDATE Statement representation.
 * This will create a statement like
 * <pre>
 * UPDATE {tbl}
 * SET {expr}={val}, {expr}={val}, ...
 * WHERE {boolExpr} [AND|OR] {boolExpr} ...
 * </pre>
 * Any joins are converted into a WHERE clause like
 * <pre>
 * EXISTS (SELECT * FROM OTHER_TBL ...)
 * </pre>
 */
public class UpdateStatement extends SQLStatement
{
    /** Array of update expressions when the statement is an UPDATE. */
    protected SQLExpression[] updates = null;

    /**
     * Constructor for an UPDATE statement.
     * @param rdbmsMgr Store Manager
     * @param table The primary table to UPDATE
     * @param alias Alias for the primary table
     * @param tableGroupName Group name for the primary table
     * @param extensions Any extensions (optional)
     */
    public UpdateStatement(RDBMSStoreManager rdbmsMgr, Table table, DatastoreIdentifier alias, String tableGroupName, Map<String, Object> extensions)
    {
        super(null, rdbmsMgr, table, alias, tableGroupName, extensions);
    }

    /**
     * Method to set the UPDATE clause of the statement.
     * @param exprs The update clause expression
     */
    public void setUpdates(SQLExpression[] exprs)
    {
        invalidateStatement();

        updates = exprs;
    }

    public boolean hasUpdates()
    {
        if (updates == null)
        {
            return false;
        }

        for (int i=0;i<updates.length;i++)
        {
            if (updates[i] != null)
            {
                return true;
            }
        }
        return false;
    }

    public synchronized SQLText getSQLText()
    {
        if (sql != null)
        {
            return sql;
        }

        // Generate the SET component of the statement since some need it to formulate the basic UPDATE component
        SQLText setSQL = new SQLText("SET ");
        if (updates != null && updates.length > 0)
        {
            for (int i=0;i<updates.length;i++)
            {
                if (updates[i] != null)
                {
                    if (i != 0)
                    {
                        setSQL.append(",");
                    }
                    setSQL.append(updates[i].toSQLText());
                }
            }
        }

        sql = rdbmsMgr.getDatastoreAdapter().getUpdateTableStatement(primaryTable, setSQL);

        if (joins != null)
        {
            // Joins present so convert to "... WHERE EXISTS (SELECT * FROM OTHER_TBL ...)"
            Iterator<SQLJoin> joinIter = joins.iterator();

            // Create sub-statement selecting the first joined table, joining back to the outer statement
            SQLJoin subJoin = joinIter.next();
            SQLStatement subStmt = new SelectStatement(this, rdbmsMgr, subJoin.getTargetTable().getTable(), subJoin.getTargetTable().getAlias(), subJoin.getTargetTable().getGroupName());
            subStmt.whereAnd(subJoin.getCondition(), false);
            if (where != null)
            {
                // Move the WHERE clause to the sub-statement
                subStmt.whereAnd(where, false);
            }

            // Put any remaining joins into the sub-statement
            while (joinIter.hasNext())
            {
                SQLJoin join = joinIter.next();
                subStmt.joins.add(join);
            }

            // Set WHERE clause of outer statement to "EXISTS (sub-statement)"
            BooleanExpression existsExpr = new BooleanSubqueryExpression(this, "EXISTS", subStmt);
            where = existsExpr;
        }
        if (where != null)
        {
            sql.append(" WHERE ").append(where.toSQLText());
        }

        return sql;
    }
}