/**
* 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.row.ValuesHolderRow;
import com.foundationdb.qp.rowtype.RowType;
import com.foundationdb.server.types.value.ValueTargets;
import com.foundationdb.server.types.texpressions.TEvaluatableExpression;
import com.foundationdb.server.types.texpressions.TPreparedExpression;
import com.foundationdb.server.explain.Attributes;
import com.foundationdb.server.explain.CompoundExplainer;
import com.foundationdb.server.explain.ExplainContext;
import com.foundationdb.server.explain.Label;
import com.foundationdb.server.explain.PrimitiveExplainer;
import com.foundationdb.server.explain.Type;
import com.foundationdb.util.ArgumentValidation;
import com.foundationdb.util.tap.InOutTap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
/**
<h1>Overview</h1>
If the input stream has no rows, the output stream contains one row, composed by a specified list of expressions.
Otherwise, the output is either the input rows or no rows at all, controlled by an InputPreservationOption.
<h1>Arguments</h1>
<ul>
<li>Operator inputOperator:</li> Operator providing input stream.
<li>RowType rowType:</li> Type of the row that is output in case the input stream is empty.
<li>List<? extends Expression>:</li> Expressions computing the columns of the row that is output
in case the input stream is empty.
<li>InputPreservationOption inputPreservation:</li> indicates whether input rows are output when present.
<ul>
<h1>Behavior</h1>
If the input stream has no rows, then a row, composed by a specified list of expressions, is written to the output
stream. Otherwise, input rows are written to output if inputPreservation is KEEP_INPUT; otherwise input rows
are not written to output.
<h1>Output</h1>
Nothing else to say.
<h1>Assumptions</h1>
None.
<h1>Performance</h1>
This operator does not IO.
<h1>Memory Requirements</h1>
None.
*/
class IfEmpty_Default extends Operator
{
// Object interface
@Override
public String toString()
{
StringBuilder buffer = new StringBuilder();
buffer.append(getClass().getSimpleName());
buffer.append('(');
boolean first = true;
List<?> toStringExpressions = pExpressions;
for (Object expression : toStringExpressions) {
if (first) {
first = false;
} else {
buffer.append(", ");
}
buffer.append(expression.toString());
}
buffer.append(", ");
buffer.append(inputPreservation);
buffer.append(')');
return buffer.toString();
}
// Operator interface
@Override
protected Cursor cursor(QueryContext context, QueryBindingsCursor bindingsCursor)
{
return new Execution(context, bindingsCursor);
}
@Override
public void findDerivedTypes(Set<RowType> derivedTypes)
{
inputOperator.findDerivedTypes(derivedTypes);
}
@Override
public List<Operator> getInputOperators()
{
ArrayList<Operator> inputOperators = new ArrayList<>(1);
inputOperators.add(inputOperator);
return inputOperators;
}
@Override
public String describePlan()
{
return describePlan(inputOperator);
}
// IfEmpty_Default interface
public IfEmpty_Default(Operator inputOperator,
RowType rowType,
List<? extends TPreparedExpression> pExpressions,
API.InputPreservationOption inputPreservation)
{
ArgumentValidation.notNull("inputOperator", inputOperator);
ArgumentValidation.notNull("rowType", rowType);
ArgumentValidation.notNull("inputPreservation", inputPreservation);
ArgumentValidation.notNull("pExpressions", pExpressions);
this.inputOperator = inputOperator;
this.rowType = rowType;
List<?> validateExprs = pExpressions;
this.pExpressions = new ArrayList<>(pExpressions);
ArgumentValidation.isEQ("rowType.nFields()", rowType.nFields(), "expressions.size()", validateExprs.size());
this.inputPreservation = inputPreservation;
}
// Class state
private static final InOutTap TAP_OPEN = OPERATOR_TAP.createSubsidiaryTap("operator: IfEmpty_Default open");
private static final InOutTap TAP_NEXT = OPERATOR_TAP.createSubsidiaryTap("operator: IfEmpty_Default next");
private static final Logger LOG = LoggerFactory.getLogger(IfEmpty_Default.class);
// Object state
private final Operator inputOperator;
private final RowType rowType;
private final List<TPreparedExpression> pExpressions;
private final API.InputPreservationOption inputPreservation;
@Override
public CompoundExplainer getExplainer(ExplainContext context)
{
Attributes atts = new Attributes();
atts.put(Label.NAME, PrimitiveExplainer.getInstance(getName()));
atts.put(Label.INPUT_TYPE, rowType.getExplainer(context));
for (TPreparedExpression ex : pExpressions)
atts.put(Label.OPERAND, ex.getExplainer(context));
atts.put(Label.INPUT_OPERATOR, inputOperator.getExplainer(context));
atts.put(Label.INPUT_PRESERVATION, PrimitiveExplainer.getInstance(inputPreservation.toString()));
return new CompoundExplainer(Type.IF_EMPTY, atts);
}
// Inner classes
enum InputState
{
UNKNOWN, DONE, ECHO_INPUT
}
private class Execution extends ChainedCursor
{
// Cursor interface
@Override
public void open()
{
TAP_OPEN.in();
try {
super.open();
this.inputState = InputState.UNKNOWN;
} finally {
TAP_OPEN.out();
}
}
@Override
public Row next()
{
if (TAP_NEXT_ENABLED) {
TAP_NEXT.in();
}
try {
if (CURSOR_LIFECYCLE_ENABLED) {
CursorLifecycle.checkIdleOrActive(this);
}
Row row = null;
checkQueryCancelation();
switch (inputState) {
case UNKNOWN:
row = input.next();
if (row == null) {
row = emptySubstitute();
inputState = InputState.DONE;
} else if (inputPreservation == API.InputPreservationOption.KEEP_INPUT) {
inputState = InputState.ECHO_INPUT;
} else {
row = null;
inputState = InputState.DONE;
}
break;
case DONE:
row = null;
break;
case ECHO_INPUT:
row = input.next();
break;
}
if (row == null) {
setIdle();
}
if (LOG_EXECUTION) {
LOG.debug("IfEmpty_Default: yield {}", row);
}
return row;
} finally {
if (TAP_NEXT_ENABLED) {
TAP_NEXT.out();
}
}
}
// Execution interface
Execution(QueryContext context, QueryBindingsCursor bindingsCursor)
{
super(context, inputOperator.cursor(context, bindingsCursor));
this.pEvaluations = new ArrayList<>(pExpressions.size());
for (TPreparedExpression outerJoinRowExpressions : pExpressions) {
TEvaluatableExpression eval = outerJoinRowExpressions.build();
pEvaluations.add(eval);
}
}
// For use by this class
private Row emptySubstitute()
{
ValuesHolderRow valuesHolderRow = new ValuesHolderRow(rowType);
int nFields = rowType.nFields();
for (int i = 0; i < nFields; i++) {
TEvaluatableExpression outerJoinRowColumnEvaluation = pEvaluations.get(i);
outerJoinRowColumnEvaluation.with(context);
outerJoinRowColumnEvaluation.with(bindings);
outerJoinRowColumnEvaluation.evaluate();
ValueTargets.copyFrom(
outerJoinRowColumnEvaluation.resultValue(),
valuesHolderRow.valueAt(i));
}
return valuesHolderRow;
}
// Object state
private final List<TEvaluatableExpression> pEvaluations;
private InputState inputState;
}
}