ColumnResolver.java

/*
 * Copyright 2014-2015 the original author or authors
 *
 * 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.
 */
package com.wplatform.ddal.dbobject.table;

import com.wplatform.ddal.command.dml.Select;
import com.wplatform.ddal.command.expression.Expression;
import com.wplatform.ddal.command.expression.ExpressionColumn;
import com.wplatform.ddal.value.Value;

/**
 * A column resolver is list of column (for example, a table) that can map a
 * column name to an actual column.
 */
public interface ColumnResolver {

    /**
     * Get the table alias.
     *
     * @return the table alias
     */
    String getTableAlias();

    /**
     * Get the column list.
     *
     * @return the column list
     */
    Column[] getColumns();

    /**
     * Get the list of system columns, if any.
     *
     * @return the system columns or null
     */
    Column[] getSystemColumns();

    /**
     * Get the row id pseudo column, if there is one.
     *
     * @return the row id column or null
     */
    Column getRowIdColumn();

    /**
     * Get the schema name.
     *
     * @return the schema name
     */
    String getSchemaName();

    /**
     * Get the value for the given column.
     *
     * @param column the column
     * @return the value
     */
    Value getValue(Column column);

    /**
     * Get the table filter.
     *
     * @return the table filter
     */
    TableFilter getTableFilter();

    /**
     * Get the select statement.
     *
     * @return the select statement
     */
    Select getSelect();

    /**
     * Get the expression that represents this column.
     *
     * @param expressionColumn the expression column
     * @param column           the column
     * @return the optimized expression
     */
    Expression optimize(ExpressionColumn expressionColumn, Column column);

}