de.akquinet.jbosscc.guttenbase.hints.impl.DefaultSplitColumn Maven / Gradle / Ivy

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package de.akquinet.jbosscc.guttenbase.hints.impl;

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

import de.akquinet.jbosscc.guttenbase.meta.ColumnMetaData;
import de.akquinet.jbosscc.guttenbase.meta.ColumnType;
import de.akquinet.jbosscc.guttenbase.meta.TableMetaData;
import de.akquinet.jbosscc.guttenbase.tools.SplitColumn;

/**
 * Sometimes the amount of data exceeds buffers. 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.
 * 
 * By default use the first primary key column, if any. Otherwise returns the first column with a numeric type. Otherwise return the first
 * column.
 * 
 * 
 * © 2012 akquinet tech@spree
 * 
 * 
 * @author M. Dahm
 */
public class DefaultSplitColumn implements SplitColumn {
	@Override
	public ColumnMetaData getSplitColumn(final TableMetaData table) throws SQLException {
		final List columns = table.getColumnMetaData();

		for (final ColumnMetaData columnMetaData : columns) {
			if (columnMetaData.isPrimaryKey()) {
				return columnMetaData;
			}
		}

		for (final ColumnMetaData columnMetaData : columns) {
			final String columnClassName = columnMetaData.getColumnClassName();

			if (ColumnType.isSupportedClass(columnClassName)) {
				final ColumnType columnType = ColumnType.valueForClass(columnClassName);

				if (columnType.isNumber()) {
					return columnMetaData;
				}
			}
		}

		return columns.get(0);
	}
}