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/*
* Copyright 2004-2009 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.apache.lucene.store.jdbc.index;
import java.io.IOException;
import java.sql.Blob;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import org.apache.lucene.store.jdbc.JdbcDirectory;
import org.apache.lucene.store.jdbc.JdbcFileEntrySettings;
import org.apache.lucene.store.jdbc.JdbcStoreException;
import org.apache.lucene.store.jdbc.support.JdbcTemplate;
/**
* An IndexInput implementation, that for every buffer refill will go and fetch
* the data from the database.
*
* @author kimchy
*/
public class FetchOnBufferReadJdbcIndexInput extends JdbcBufferedIndexInput {
private String name;
// lazy intialize the length
private long totalLength = -1;
private long position = 1;
private JdbcDirectory jdbcDirectory;
public void configure(String name, JdbcDirectory jdbcDirectory, JdbcFileEntrySettings settings) throws IOException {
super.configure(name, jdbcDirectory, settings);
this.jdbcDirectory = jdbcDirectory;
this.name = name;
}
// Overriding refill here since we can execute a single query to get both the length and the buffer data
// resulted in not the nicest OO design, where the buffer information is protected in the JdbcBufferedIndexInput class
// and code duplication between this method and JdbcBufferedIndexInput.
// Performance is much better this way!
protected void refill() throws IOException {
jdbcDirectory.getJdbcTemplate().executeSelect(jdbcDirectory.getTable().sqlSelectSizeValueByName(),
new JdbcTemplate.ExecuteSelectCallback() {
public void fillPrepareStatement(PreparedStatement ps) throws Exception {
ps.setFetchSize(1);
ps.setString(1, name);
}
public Object execute(ResultSet rs) throws Exception {
// START read blob and update length if required
if (!rs.next()) {
throw new JdbcStoreException("No entry for [" + name + "] table " + jdbcDirectory.getTable());
}
synchronized (this) {
if (totalLength == -1) {
totalLength = rs.getLong(3);
}
}
// END read blob and update length if required
long start = bufferStart + bufferPosition;
long end = start + bufferSize;
if (end > length()) // don't read past EOF
end = length();
bufferLength = (int) (end - start);
if (bufferLength <= 0)
throw new IOException("read past EOF");
if (buffer == null) {
buffer = new byte[bufferSize]; // allocate buffer lazily
seekInternal(bufferStart);
}
// START replace read internal
Blob blob = rs.getBlob(2);
readInternal(blob, buffer, 0, bufferLength);
bufferStart = start;
bufferPosition = 0;
return null;
}
});
}
protected synchronized void readInternal(final byte[] b, final int offset, final int length) throws IOException {
jdbcDirectory.getJdbcTemplate().executeSelect(jdbcDirectory.getTable().sqlSelectSizeValueByName(),
new JdbcTemplate.ExecuteSelectCallback() {
public void fillPrepareStatement(PreparedStatement ps) throws Exception {
ps.setFetchSize(1);
ps.setString(1, name);
}
public Object execute(ResultSet rs) throws Exception {
if (!rs.next()) {
throw new JdbcStoreException("No entry for [" + name + "] table " + jdbcDirectory.getTable());
}
Blob blob = rs.getBlob(2);
readInternal(blob, b, offset, length);
synchronized (this) {
if (FetchOnBufferReadJdbcIndexInput.this.totalLength == -1) {
FetchOnBufferReadJdbcIndexInput.this.totalLength = rs.getLong(3);
}
}
return null;
}
});
}
/**
* A helper methods that already reads an open blob
*/
private synchronized void readInternal(Blob blob, final byte[] b, final int offset, final int length) throws Exception {
long curPos = getFilePointer();
if (curPos + 1 != position) {
position = curPos + 1;
}
byte[] bytesRead = blob.getBytes(position, length);
if (bytesRead.length != length) {
throw new IOException("read past EOF");
}
System.arraycopy(bytesRead, 0, b, offset, length);
position += bytesRead.length;
}
protected void seekInternal(long pos) throws IOException {
this.position = pos + 1;
}
public void close() throws IOException {
}
public synchronized long length() {
if (totalLength == -1) {
try {
this.totalLength = jdbcDirectory.fileLength(name);
} catch (IOException e) {
// do nothing here for now, much better for performance
}
}
return totalLength;
}
}