/*
 * Copyright 2002-2018 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 org.springframework.jdbc.object;

import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.Iterator;
import java.util.List;
import javax.sql.DataSource;

import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BatchPreparedStatementSetter;

SqlUpdate subclass that performs batch update operations. Encapsulates queuing up records to be updated, and adds them as a single batch once flush is called or the given batch size has been met. 
Note that this class is a non-thread-safe object, in contrast to all other JDBC operations objects in this package. You need to create a new instance of it for each use, or call reset before reuse within the same thread. 
Author:
Keith Donald, Juergen Hoeller
See Also:
flush
reset
Since:
1.1/**
 * SqlUpdate subclass that performs batch update operations. Encapsulates
 * queuing up records to be updated, and adds them as a single batch once
 * {@code flush} is called or the given batch size has been met.
 *
 * <p>Note that this class is a <b>non-thread-safe object</b>, in contrast
 * to all other JDBC operations objects in this package. You need to create
 * a new instance of it for each use, or call {@code reset} before
 * reuse within the same thread.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @since 1.1
 * @see #flush
 * @see #reset
 */
public class BatchSqlUpdate extends SqlUpdate {

	
Default number of inserts to accumulate before committing a batch (5000).
/**
	 * Default number of inserts to accumulate before committing a batch (5000).
	 */
	public static final int DEFAULT_BATCH_SIZE = 5000;


	private int batchSize = DEFAULT_BATCH_SIZE;

	private boolean trackRowsAffected = true;

	private final Deque<Object[]> parameterQueue = new ArrayDeque<>();

	private final List<Integer> rowsAffected = new ArrayList<>();


	
Constructor to allow use as a JavaBean. DataSource and SQL
must be supplied before compilation and use.
See Also:
setDataSource
RdbmsOperation.setSql/**
	 * Constructor to allow use as a JavaBean. DataSource and SQL
	 * must be supplied before compilation and use.
	 * @see #setDataSource
	 * @see #setSql
	 */
	public BatchSqlUpdate() {
		super();
	}

	
Construct an update object with a given DataSource and SQL.
Params:
ds – the DataSource to use to obtain connections
sql – the SQL statement to execute/**
	 * Construct an update object with a given DataSource and SQL.
	 * @param ds the DataSource to use to obtain connections
	 * @param sql the SQL statement to execute
	 */
	public BatchSqlUpdate(DataSource ds, String sql) {
		super(ds, sql);
	}

	
Construct an update object with a given DataSource, SQL
and anonymous parameters.
Params:
ds – the DataSource to use to obtain connections
sql – the SQL statement to execute
types – the SQL types of the parameters, as defined in the java.sql.Types class
See Also:
Types/**
	 * Construct an update object with a given DataSource, SQL
	 * and anonymous parameters.
	 * @param ds the DataSource to use to obtain connections
	 * @param sql the SQL statement to execute
	 * @param types the SQL types of the parameters, as defined in the
	 * {@code java.sql.Types} class
	 * @see java.sql.Types
	 */
	public BatchSqlUpdate(DataSource ds, String sql, int[] types) {
		super(ds, sql, types);
	}

	
Construct an update object with a given DataSource, SQL,
anonymous parameters and specifying the maximum number of rows
that may be affected.
Params:
ds – the DataSource to use to obtain connections
sql – the SQL statement to execute
types – the SQL types of the parameters, as defined in the java.sql.Types class
batchSize – the number of statements that will trigger
an automatic intermediate flush
See Also:
Types/**
	 * Construct an update object with a given DataSource, SQL,
	 * anonymous parameters and specifying the maximum number of rows
	 * that may be affected.
	 * @param ds the DataSource to use to obtain connections
	 * @param sql the SQL statement to execute
	 * @param types the SQL types of the parameters, as defined in the
	 * {@code java.sql.Types} class
	 * @param batchSize the number of statements that will trigger
	 * an automatic intermediate flush
	 * @see java.sql.Types
	 */
	public BatchSqlUpdate(DataSource ds, String sql, int[] types, int batchSize) {
		super(ds, sql, types);
		setBatchSize(batchSize);
	}


	
Set the number of statements that will trigger an automatic intermediate flush. update calls or the given statement parameters will be queued until the batch size is met, at which point it will empty the queue and execute the batch. 
You can also flush already queued statements with an explicit flush call. Note that you need to this after queueing all parameters to guarantee that all statements have been flushed. /**
	 * Set the number of statements that will trigger an automatic intermediate
	 * flush. {@code update} calls or the given statement parameters will
	 * be queued until the batch size is met, at which point it will empty the
	 * queue and execute the batch.
	 * <p>You can also flush already queued statements with an explicit
	 * {@code flush} call. Note that you need to this after queueing
	 * all parameters to guarantee that all statements have been flushed.
	 */
	public void setBatchSize(int batchSize) {
		this.batchSize = batchSize;
	}

	
Set whether to track the rows affected by batch updates performed
by this operation object.
Default is "true". Turn this off to save the memory needed for
the list of row counts.
See Also:
getRowsAffected()/**
	 * Set whether to track the rows affected by batch updates performed
	 * by this operation object.
	 * <p>Default is "true". Turn this off to save the memory needed for
	 * the list of row counts.
	 * @see #getRowsAffected()
	 */
	public void setTrackRowsAffected(boolean trackRowsAffected) {
		this.trackRowsAffected = trackRowsAffected;
	}

	
BatchSqlUpdate does not support BLOB or CLOB parameters.
/**
	 * BatchSqlUpdate does not support BLOB or CLOB parameters.
	 */
	@Override
	protected boolean supportsLobParameters() {
		return false;
	}


	
Overridden version of update that adds the given statement parameters to the queue rather than executing them immediately. All other update methods of the SqlUpdate base class go through this method and will thus behave similarly. 
You need to call flush to actually execute the batch. If the specified batch size is reached, an implicit flush will happen; you still need to finally call flush to flush all statements. 
Params:
params – array of parameter objects
See Also:
flush
Returns:
the number of rows affected by the update (always -1,
meaning "not applicable", as the statement is not actually
executed by this method)/**
	 * Overridden version of {@code update} that adds the given statement
	 * parameters to the queue rather than executing them immediately.
	 * All other {@code update} methods of the SqlUpdate base class go
	 * through this method and will thus behave similarly.
	 * <p>You need to call {@code flush} to actually execute the batch.
	 * If the specified batch size is reached, an implicit flush will happen;
	 * you still need to finally call {@code flush} to flush all statements.
	 * @param params array of parameter objects
	 * @return the number of rows affected by the update (always -1,
	 * meaning "not applicable", as the statement is not actually
	 * executed by this method)
	 * @see #flush
	 */
	@Override
	public int update(Object... params) throws DataAccessException {
		validateParameters(params);
		this.parameterQueue.add(params.clone());

		if (this.parameterQueue.size() == this.batchSize) {
			if (logger.isDebugEnabled()) {
				logger.debug("Triggering auto-flush because queue reached batch size of " + this.batchSize);
			}
			flush();
		}

		return -1;
	}

	
Trigger any queued update operations to be added as a final batch.
Returns:
an array of the number of rows affected by each statement/**
	 * Trigger any queued update operations to be added as a final batch.
	 * @return an array of the number of rows affected by each statement
	 */
	public int[] flush() {
		if (this.parameterQueue.isEmpty()) {
			return new int[0];
		}

		int[] rowsAffected = getJdbcTemplate().batchUpdate(
				resolveSql(),
				new BatchPreparedStatementSetter() {
					@Override
					public int getBatchSize() {
						return parameterQueue.size();
					}
					@Override
					public void setValues(PreparedStatement ps, int index) throws SQLException {
						Object[] params = parameterQueue.removeFirst();
						newPreparedStatementSetter(params).setValues(ps);
					}
				});

		for (int rowCount : rowsAffected) {
			checkRowsAffected(rowCount);
			if (this.trackRowsAffected) {
				this.rowsAffected.add(rowCount);
			}
		}

		return rowsAffected;
	}

	
Return the current number of statements or statement parameters
in the queue.
/**
	 * Return the current number of statements or statement parameters
	 * in the queue.
	 */
	public int getQueueCount() {
		return this.parameterQueue.size();
	}

	
Return the number of already executed statements.
/**
	 * Return the number of already executed statements.
	 */
	public int getExecutionCount() {
		return this.rowsAffected.size();
	}

	
Return the number of affected rows for all already executed statements. Accumulates all of flush's return values until reset is invoked. 
See Also:
reset
Returns:
an array of the number of rows affected by each statement/**
	 * Return the number of affected rows for all already executed statements.
	 * Accumulates all of {@code flush}'s return values until
	 * {@code reset} is invoked.
	 * @return an array of the number of rows affected by each statement
	 * @see #reset
	 */
	public int[] getRowsAffected() {
		int[] result = new int[this.rowsAffected.size()];
		int i = 0;
		for (Iterator<Integer> it = this.rowsAffected.iterator(); it.hasNext(); i++) {
			result[i] = it.next();
		}
		return result;
	}

	
Reset the statement parameter queue, the rows affected cache,
and the execution count.
/**
	 * Reset the statement parameter queue, the rows affected cache,
	 * and the execution count.
	 */
	public void reset() {
		this.parameterQueue.clear();
		this.rowsAffected.clear();
	}

}