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This module bridges Table/SQL API and runtime. It contains all resources that are required during pre-flight and runtime phase. The content of this module is work-in-progress. It will replace flink-table-planner once it is stable. See FLINK-11439 and FLIP-32 for more details.
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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.flink.table.planner.plan.type;

import org.apache.flink.table.planner.calcite.FlinkTypeFactory;
import org.apache.flink.table.types.logical.DecimalType;
import org.apache.flink.table.types.logical.MapType;
import org.apache.flink.table.types.logical.VarCharType;
import org.apache.flink.table.types.logical.utils.LogicalTypeMerging;

import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.sql.SqlOperatorBinding;
import org.apache.calcite.sql.type.OrdinalReturnTypeInference;
import org.apache.calcite.sql.type.ReturnTypes;
import org.apache.calcite.sql.type.SqlReturnTypeInference;
import org.apache.calcite.sql.type.SqlTypeName;
import org.apache.calcite.sql.type.SqlTypeTransforms;

import java.math.BigDecimal;

/** Type inference in Flink. */
public class FlinkReturnTypes {

    /** ROUND(num [,len]) type inference. */
    public static final SqlReturnTypeInference ROUND_FUNCTION =
            new SqlReturnTypeInference() {
                @Override
                public RelDataType inferReturnType(SqlOperatorBinding opBinding) {
                    final RelDataType numType = opBinding.getOperandType(0);
                    if (numType.getSqlTypeName() != SqlTypeName.DECIMAL) {
                        return numType;
                    }
                    final BigDecimal lenVal;
                    if (opBinding.getOperandCount() == 1) {
                        lenVal = BigDecimal.ZERO;
                    } else if (opBinding.getOperandCount() == 2) {
                        lenVal = getArg1Literal(opBinding); // may return null
                    } else {
                        throw new AssertionError();
                    }
                    if (lenVal == null) {
                        return numType; //
                    }
                    // ROUND( decimal(p,s), r )
                    final int p = numType.getPrecision();
                    final int s = numType.getScale();
                    final int r = lenVal.intValueExact();
                    DecimalType dt = LogicalTypeMerging.findRoundDecimalType(p, s, r);
                    return opBinding
                            .getTypeFactory()
                            .createSqlType(SqlTypeName.DECIMAL, dt.getPrecision(), dt.getScale());
                }

                private BigDecimal getArg1Literal(SqlOperatorBinding opBinding) {
                    try {
                        return opBinding.getOperandLiteralValue(1, BigDecimal.class);
                    } catch (Throwable e) {
                        return null;
                    }
                }
            };

    /**
     * Type-inference strategy whereby the result type of a call is the type of the operand #0
     * (0-based), with nulls always allowed.
     */
    public static final SqlReturnTypeInference ARG0_VARCHAR_FORCE_NULLABLE =
            new OrdinalReturnTypeInference(0) {
                @Override
                public RelDataType inferReturnType(SqlOperatorBinding opBinding) {
                    RelDataType type = super.inferReturnType(opBinding);
                    RelDataType newType;
                    switch (type.getSqlTypeName()) {
                        case CHAR:
                            newType =
                                    opBinding
                                            .getTypeFactory()
                                            .createSqlType(
                                                    SqlTypeName.VARCHAR, type.getPrecision());
                            break;
                        case VARCHAR:
                            newType = type;
                            break;
                        default:
                            throw new UnsupportedOperationException("Unsupported type: " + type);
                    }
                    return opBinding.getTypeFactory().createTypeWithNullability(newType, true);
                }
            };

    /** Type-inference strategy that always returns "VARCHAR(2000)" with nulls always allowed. */
    public static final SqlReturnTypeInference VARCHAR_2000_NULLABLE =
            ReturnTypes.cascade(ReturnTypes.VARCHAR_2000, SqlTypeTransforms.FORCE_NULLABLE);

    public static final SqlReturnTypeInference ROUND_FUNCTION_NULLABLE =
            ReturnTypes.cascade(ROUND_FUNCTION, SqlTypeTransforms.TO_NULLABLE);

    public static final SqlReturnTypeInference NUMERIC_FROM_ARG1_DEFAULT1 =
            new NumericOrDefaultReturnTypeInference(1, 1);

    public static final SqlReturnTypeInference NUMERIC_FROM_ARG1_DEFAULT1_NULLABLE =
            ReturnTypes.cascade(NUMERIC_FROM_ARG1_DEFAULT1, SqlTypeTransforms.TO_NULLABLE);

    public static final SqlReturnTypeInference STR_MAP_NULLABLE =
            ReturnTypes.explicit(
                    factory ->
                            ((FlinkTypeFactory) factory)
                                    .createFieldTypeFromLogicalType(
                                            new MapType(
                                                    new VarCharType(VarCharType.MAX_LENGTH),
                                                    new VarCharType(VarCharType.MAX_LENGTH))));
}