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

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package de.akquinet.jbosscc.guttenbase.statements;

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

/**
 * Sometimes the amount of data in the result set 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.
 *
 * With this statement we count the number of rows that actually will be read for the given chunk.
 *
 * 
 * © 2012-2020 akquinet tech@spree
 * 
 *
 * Hint is used by {@link SplitColumnHint}
 * @author M. Dahm
 */
public class SplitByColumnSelectCountStatementCreator extends AbstractSelectStatementCreator {
	public SplitByColumnSelectCountStatementCreator(final ConnectorRepository connectorRepository, final String connectorId) {
		super(connectorRepository, connectorId);
	}

	@Override
	protected String createColumnClause(final List columns) throws SQLException {
		return "COUNT(*)";
	}

	@Override
	protected String createWhereClause(final TableMetaData tableMetaData) throws SQLException {
		final ColumnMetaData splitColumn = _connectorRepository.getConnectorHint(_connectorId, SplitColumn.class).getValue()
				.getSplitColumn(tableMetaData);

		return "WHERE " + splitColumn.getColumnName() + " BETWEEN ? AND ?";
	}
}