/**
* 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.server.types.common.funcs;
import com.foundationdb.server.types.LazyList;
import com.foundationdb.server.types.TClass;
import com.foundationdb.server.types.TExecutionContext;
import com.foundationdb.server.types.TOverloadResult;
import com.foundationdb.server.types.TPreptimeContext;
import com.foundationdb.server.types.TPreptimeValue;
import com.foundationdb.server.types.TScalar;
import com.foundationdb.server.types.value.ValueSource;
import com.foundationdb.server.types.value.ValueTarget;
import com.foundationdb.server.types.texpressions.Constantness;
import com.foundationdb.server.types.texpressions.TInputSetBuilder;
import com.foundationdb.server.types.texpressions.TScalarBase;
/**
* <p>A function for describing the prepare-time type information of other expression. If/when we divide bundles into
* modular packages, this should go into a testing or debug package. Its primary purpose, at least for now, is to verify
* in our yaml tests that expressions have the right type.</p>
*
* <p>The usage is <code>DESCRIBE_EXPRESSION(<i>expr</i>)</code>, and the result is a constant {@code VARCHAR(255)} which
* describes the TInstance and constantness of <i>expr</i>.</p>
*/
public final class DescribeExpression extends TScalarBase {
@Override
protected void buildInputSets(TInputSetBuilder builder) {
builder.covers(null, 0);
}
@Override
protected void doEvaluate(TExecutionContext context, LazyList<? extends ValueSource> inputs, ValueTarget output) {
String result = context.inputTypeAt(0).toString();
ValueSource input = inputs.get(0);
result = ( (input== null) ? "variable " : "const ") + result;
output.putString(result, null);
}
@Override
protected boolean nullContaminates(int inputIndex) {
return false;
}
@Override
protected Constantness constness(TPreptimeContext context, int inputIndex, LazyList<? extends TPreptimeValue> values) {
return Constantness.CONST;
}
@Override
protected boolean allowNonConstsInEvaluation() {
return true;
}
@Override
public String displayName() {
return "describe_expression";
}
@Override
public TOverloadResult resultType() {
return TOverloadResult.fixed(varchar, 255);
}
private final TClass varchar;
public DescribeExpression(TClass varchar) {
this.varchar = varchar;
}
}