de.akquinet.jbosscc.guttenbase.statements.SplitByColumnSelectMinMaxStatementCreator Maven / Gradle / Ivy

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package de.akquinet.jbosscc.guttenbase.statements;

import java.sql.SQLException;
import java.util.List;

import de.akquinet.jbosscc.guttenbase.hints.SplitColumnHint;
import de.akquinet.jbosscc.guttenbase.meta.ColumnMetaData;
import de.akquinet.jbosscc.guttenbase.meta.TableMetaData;
import de.akquinet.jbosscc.guttenbase.repository.ConnectorRepository;
import de.akquinet.jbosscc.guttenbase.tools.SplitColumn;

/**
 * Sometimes the amount of data exceeds any buffer. In these cases we need to split the data by some given range, usually the primary key.
 * I.e., the data is read in chunks where these chunks are split using the ID column range of values.
 * 
 * Read minimum and maxim value of that column.
 * 
 * 
 * © 2012 akquinet tech@spree
 * 
 * 
 * @Uses-Hint {@link SplitColumnHint}
 * @author M. Dahm
 */
public class SplitByColumnSelectMinMaxStatementCreator extends AbstractSelectStatementCreator {
	public SplitByColumnSelectMinMaxStatementCreator(final ConnectorRepository connectorRepository, final String connectorId) {
		super(connectorRepository, connectorId);
	}

	@Override
	protected String createColumnClause(final List columns) throws SQLException {
		assert !columns.isEmpty();
		final TableMetaData tableMetaData = columns.get(0).getTableMetaData();
		final ColumnMetaData splitColumn = _connectorRepository.getConnectorHint(_connectorId, SplitColumn.class).getValue()
				.getSplitColumn(tableMetaData);

		return "MIN(" + splitColumn.getColumnName() + "), MAX(" + splitColumn.getColumnName() + ")";
	}
}