org.h2.result.ResultRemote Maven / Gradle / Ivy
/*
* Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.result;
import java.io.IOException;
import java.util.ArrayList;
import org.h2.engine.SessionInterface;
import org.h2.engine.SessionRemote;
import org.h2.engine.SysProperties;
import org.h2.message.DbException;
import org.h2.message.Trace;
import org.h2.value.Transfer;
import org.h2.value.TypeInfo;
import org.h2.value.Value;
/**
* The client side part of a result set that is kept on the server.
* In many cases, the complete data is kept on the client side,
* but for large results only a subset is in-memory.
*/
public class ResultRemote implements ResultInterface {
private int fetchSize;
private SessionRemote session;
private Transfer transfer;
private int id;
private final ResultColumn[] columns;
private Value[] currentRow;
private final int rowCount;
private int rowId, rowOffset;
private ArrayList result;
private final Trace trace;
public ResultRemote(SessionRemote session, Transfer transfer, int id,
int columnCount, int fetchSize) throws IOException {
this.session = session;
trace = session.getTrace();
this.transfer = transfer;
this.id = id;
this.columns = new ResultColumn[columnCount];
rowCount = transfer.readInt();
for (int i = 0; i < columnCount; i++) {
columns[i] = new ResultColumn(transfer);
}
rowId = -1;
result = new ArrayList<>(Math.min(fetchSize, rowCount));
this.fetchSize = fetchSize;
fetchRows(false);
}
@Override
public boolean isLazy() {
return false;
}
@Override
public String getAlias(int i) {
return columns[i].alias;
}
@Override
public String getSchemaName(int i) {
return columns[i].schemaName;
}
@Override
public String getTableName(int i) {
return columns[i].tableName;
}
@Override
public String getColumnName(int i) {
return columns[i].columnName;
}
@Override
public TypeInfo getColumnType(int i) {
return columns[i].columnType;
}
@Override
public boolean isAutoIncrement(int i) {
return columns[i].autoIncrement;
}
@Override
public int getNullable(int i) {
return columns[i].nullable;
}
@Override
public void reset() {
rowId = -1;
currentRow = null;
if (session == null) {
return;
}
synchronized (session) {
session.checkClosed();
try {
session.traceOperation("RESULT_RESET", id);
transfer.writeInt(SessionRemote.RESULT_RESET).writeInt(id).flush();
} catch (IOException e) {
throw DbException.convertIOException(e, null);
}
}
}
@Override
public Value[] currentRow() {
return currentRow;
}
@Override
public boolean next() {
if (rowId < rowCount) {
rowId++;
remapIfOld();
if (rowId < rowCount) {
if (rowId - rowOffset >= result.size()) {
fetchRows(true);
}
currentRow = result.get(rowId - rowOffset);
return true;
}
currentRow = null;
}
return false;
}
@Override
public int getRowId() {
return rowId;
}
@Override
public boolean isAfterLast() {
return rowId >= rowCount;
}
@Override
public int getVisibleColumnCount() {
return columns.length;
}
@Override
public int getRowCount() {
return rowCount;
}
@Override
public boolean hasNext() {
return rowId < rowCount - 1;
}
private void sendClose() {
if (session == null) {
return;
}
// TODO result sets: no reset possible for larger remote result sets
try {
synchronized (session) {
session.traceOperation("RESULT_CLOSE", id);
transfer.writeInt(SessionRemote.RESULT_CLOSE).writeInt(id);
}
} catch (IOException e) {
trace.error(e, "close");
} finally {
transfer = null;
session = null;
}
}
@Override
public void close() {
result = null;
sendClose();
}
private void remapIfOld() {
if (session == null) {
return;
}
try {
if (id <= session.getCurrentId() - SysProperties.SERVER_CACHED_OBJECTS / 2) {
// object is too old - we need to map it to a new id
int newId = session.getNextId();
session.traceOperation("CHANGE_ID", id);
transfer.writeInt(SessionRemote.CHANGE_ID).writeInt(id).writeInt(newId);
id = newId;
// TODO remote result set: very old result sets may be
// already removed on the server (theoretically) - how to
// solve this?
}
} catch (IOException e) {
throw DbException.convertIOException(e, null);
}
}
private void fetchRows(boolean sendFetch) {
synchronized (session) {
session.checkClosed();
try {
rowOffset += result.size();
result.clear();
int fetch = Math.min(fetchSize, rowCount - rowOffset);
if (sendFetch) {
session.traceOperation("RESULT_FETCH_ROWS", id);
transfer.writeInt(SessionRemote.RESULT_FETCH_ROWS).
writeInt(id).writeInt(fetch);
session.done(transfer);
}
for (int r = 0; r < fetch; r++) {
boolean row = transfer.readBoolean();
if (!row) {
break;
}
int len = columns.length;
Value[] values = new Value[len];
for (int i = 0; i < len; i++) {
Value v = transfer.readValue();
values[i] = v;
}
result.add(values);
}
if (rowOffset + result.size() >= rowCount) {
sendClose();
}
} catch (IOException e) {
throw DbException.convertIOException(e, null);
}
}
}
@Override
public String toString() {
return "columns: " + columns.length + " rows: " + rowCount + " pos: " + rowId;
}
@Override
public int getFetchSize() {
return fetchSize;
}
@Override
public void setFetchSize(int fetchSize) {
this.fetchSize = fetchSize;
}
@Override
public boolean needToClose() {
return true;
}
@Override
public ResultInterface createShallowCopy(SessionInterface targetSession) {
// The operation is not supported on remote result.
return null;
}
@Override
public boolean isClosed() {
return result == null;
}
}