/**
* Copyright (C) 2009-2013 FoundationDB, LLC
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package com.foundationdb.qp.operator;
import com.foundationdb.qp.row.Row;
import com.foundationdb.qp.rowtype.RowType;
import com.foundationdb.server.error.NegativeLimitException;
import com.foundationdb.server.explain.*;
import com.foundationdb.server.types.TExecutionContext;
import com.foundationdb.server.types.TInstance;
import com.foundationdb.server.types.mcompat.mtypes.MNumeric;
import com.foundationdb.server.types.value.Value;
import com.foundationdb.server.types.value.ValueSource;
import com.foundationdb.util.ArgumentValidation;
import com.foundationdb.util.tap.InOutTap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Collections;
import java.util.List;
import java.util.Set;
/**
<h1>Overview</h1>
Provides a very simple, count-based limit.
<h1>Arguments</h1>
<ul>
<li><b>PhysicalOperator inputOperator:</b> The input operator, whose
cursor will be limited
<li><b>int limit:</b> the number of rows to limit to; cannot be
negative
</ul>
<h1>Behavior</h1>
Limit_Default's cursor returns at most <i>limit</i> rows from the input
operator's cursor. When the limit is reached, the input cursor is
automatically closed, and all subsequent calls to <i>next</i> will return
<i>false</i>.
<h1>Output</h1>
Nothing else to say.
<h1>Assumptions</h1>
None.
<h1>Performance</h1>
Essentially free.
<h1>Memory Requirements</h1>
None.
*/
final class Limit_Default extends Operator
{
// Operator interface
@Override
protected Cursor cursor(QueryContext context, QueryBindingsCursor bindingsCursor) {
return new Execution(context, inputOperator.cursor(context, bindingsCursor));
}
// Plannable interface
@Override
public void findDerivedTypes(Set<RowType> derivedTypes)
{
inputOperator.findDerivedTypes(derivedTypes);
}
@Override
public List<Operator> getInputOperators() {
return Collections.singletonList(inputOperator);
}
@Override
public String describePlan() {
return super.describePlan();
}
// Object interface
@Override
public String toString() {
StringBuilder str = new StringBuilder(getClass().getSimpleName());
str.append("(");
if (skip > 0) {
str.append(String.format("skip=%d", skip));
}
if ((limit >= 0) && (limit < Integer.MAX_VALUE)) {
if (skip > 0) str.append(", ");
str.append(String.format("limit=%d", limit));
}
str.append(": ");
str.append(inputOperator);
str.append(")");
return str.toString();
}
// Limit_Default interface
Limit_Default(Operator inputOperator, int limit) {
this(inputOperator, 0, false, limit, false);
}
Limit_Default(Operator inputOperator,
int skip, boolean skipIsBinding,
int limit, boolean limitIsBinding) {
ArgumentValidation.isGTE("skip", skip, 0);
ArgumentValidation.isGTE("limit", limit, 0);
this.skip = skip;
this.skipIsBinding = skipIsBinding;
this.limit = limit;
this.limitIsBinding = limitIsBinding;
this.inputOperator = inputOperator;
}
public int skip() {
return skip;
}
public boolean isSkipBinding() {
return skipIsBinding;
}
public int limit() {
return limit;
}
public boolean isLimitBinding() {
return limitIsBinding;
}
// Class state
private static final InOutTap TAP_OPEN = OPERATOR_TAP.createSubsidiaryTap("operator: Limit_Default open");
private static final InOutTap TAP_NEXT = OPERATOR_TAP.createSubsidiaryTap("operator: Limit_Default next");
private static final Logger LOG = LoggerFactory.getLogger(Limit_Default.class);
// Object state
private final int skip, limit;
private final boolean skipIsBinding, limitIsBinding;
private final Operator inputOperator;
@Override
public CompoundExplainer getExplainer(ExplainContext context)
{
Attributes atts = new Attributes();
atts.put(Label.NAME, PrimitiveExplainer.getInstance(getName()));
atts.put(Label.LIMIT, PrimitiveExplainer.getInstance(limit));
atts.put(Label.INPUT_OPERATOR, inputOperator.getExplainer(context));
return new CompoundExplainer(Type.LIMIT_OPERATOR, atts);
}
// internal classes
private class Execution extends ChainedCursor {
// Cursor interface
@Override
public void open() {
TAP_OPEN.in();
try {
if (isSkipBinding()) {
ValueSource value = bindings.getValue(skip());
if (!value.isNull())
this.skipLeft = value.getInt32();
}
else {
this.skipLeft = skip();
}
if (skipLeft < 0)
throw new NegativeLimitException("OFFSET", skipLeft);
if (isLimitBinding()) {
ValueSource value = bindings.getValue(limit());
if (value.isNull())
this.limitLeft = Integer.MAX_VALUE;
else {
TInstance type = MNumeric.INT.instance(true);
TExecutionContext executionContext =
new TExecutionContext(null, type, context);
Value ivalue = new Value(MNumeric.INT.instance(true));
MNumeric.INT.fromObject(executionContext, value, ivalue);
this.limitLeft = ivalue.getInt32();
}
}
else {
this.limitLeft = limit();
}
if (limitLeft < 0)
throw new NegativeLimitException("LIMIT", limitLeft);
super.open();
} finally {
TAP_OPEN.out();
}
}
@Override
public void close() {
// Because the checks in open() may
// prevent the cursor from being opened.
if (!isClosed()) {
super.close();
}
}
@Override
public Row next() {
if (TAP_NEXT_ENABLED) {
TAP_NEXT.in();
}
try {
if (CURSOR_LIFECYCLE_ENABLED) {
CursorLifecycle.checkIdleOrActive(this);
}
checkQueryCancelation();
Row row;
while (skipLeft > 0) {
if ((row = input.next()) == null) {
skipLeft = 0;
limitLeft = -1;
setIdle();
if (LOG_EXECUTION) {
LOG.debug("Limit_Default: skipLeft until complete yield null");
}
return null;
}
skipLeft--;
}
if (limitLeft < 0) {
setIdle();
if (LOG_EXECUTION) {
LOG.debug("Limit_Default: limitLeft < 0, yield null");
}
return null;
}
if (limitLeft == 0) {
setIdle();
if (LOG_EXECUTION) {
LOG.debug("Limit_Default: limitLeft == 0, yield null");
}
return null;
}
if ((row = input.next()) == null) {
limitLeft = -1;
setIdle();
if (LOG_EXECUTION) {
LOG.debug("Limit_Default: yield null");
}
return null;
}
--limitLeft;
if (LOG_EXECUTION) {
LOG.debug("Limit_Default: yield {}", row);
}
return row;
} finally {
if (TAP_NEXT_ENABLED) {
TAP_NEXT.out();
}
}
}
// Execution interface
Execution(QueryContext context, Cursor input) {
super(context, input);
}
// object state
private int skipLeft, limitLeft;
}
}