dawidwys commented on a change in pull request #8874: [FLINK-12968][table-common] Add a utility for logical type casts URL: https://github.com/apache/flink/pull/8874#discussion_r297549502
########## File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/logical/utils/LogicalTypeCasts.java ########## @@ -0,0 +1,354 @@ +/* + * 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.types.logical.utils; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.table.types.logical.DateType; +import org.apache.flink.table.types.logical.DistinctType; +import org.apache.flink.table.types.logical.LogicalType; +import org.apache.flink.table.types.logical.LogicalTypeFamily; +import org.apache.flink.table.types.logical.LogicalTypeRoot; + +import java.util.Arrays; +import java.util.HashMap; +import java.util.HashSet; +import java.util.List; +import java.util.Map; +import java.util.Set; + +import static org.apache.flink.table.types.logical.LogicalTypeFamily.BINARY_STRING; +import static org.apache.flink.table.types.logical.LogicalTypeFamily.CHARACTER_STRING; +import static org.apache.flink.table.types.logical.LogicalTypeFamily.CONSTRUCTED; +import static org.apache.flink.table.types.logical.LogicalTypeFamily.DATETIME; +import static org.apache.flink.table.types.logical.LogicalTypeFamily.EXACT_NUMERIC; +import static org.apache.flink.table.types.logical.LogicalTypeFamily.INTERVAL; +import static org.apache.flink.table.types.logical.LogicalTypeFamily.NUMERIC; +import static org.apache.flink.table.types.logical.LogicalTypeFamily.PREDEFINED; +import static org.apache.flink.table.types.logical.LogicalTypeFamily.TIME; +import static org.apache.flink.table.types.logical.LogicalTypeFamily.TIMESTAMP; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.ANY; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.BIGINT; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.BINARY; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.BOOLEAN; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.CHAR; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.DATE; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.DECIMAL; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.DISTINCT_TYPE; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.DOUBLE; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.FLOAT; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.INTEGER; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.INTERVAL_DAY_TIME; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.INTERVAL_YEAR_MONTH; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.NULL; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.SMALLINT; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.STRUCTURED_TYPE; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.SYMBOL; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.TIMESTAMP_WITHOUT_TIME_ZONE; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.TIMESTAMP_WITH_LOCAL_TIME_ZONE; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.TIMESTAMP_WITH_TIME_ZONE; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.TIME_WITHOUT_TIME_ZONE; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.TINYINT; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.VARBINARY; +import static org.apache.flink.table.types.logical.LogicalTypeRoot.VARCHAR; +import static org.apache.flink.table.types.logical.utils.LogicalTypeChecks.hasFamily; +import static org.apache.flink.table.types.logical.utils.LogicalTypeChecks.isSingleFieldInterval; + +/** + * Utilities for casting {@link LogicalType}. + * + * <p>This class aims to be compatible with the SQL standard cast specification. + * + * <p>Conversions that are defined by the {@link LogicalType} (e.g. interpreting a {@link DateType} + * as integer value) are not considered here. They are an internal bridging feature that is not + * standard compliant. If at all, {@code CONVERT} methods should make such conversions available. + */ +@Internal +public final class LogicalTypeCasts { + + private static final Map<LogicalTypeRoot, Set<LogicalTypeRoot>> implicitCastingRules; + + private static final Map<LogicalTypeRoot, Set<LogicalTypeRoot>> explicitCastingRules; + + static { + implicitCastingRules = new HashMap<>(); + explicitCastingRules = new HashMap<>(); + + // identity casts + + for (LogicalTypeRoot typeRoot : allTypes()) { + castTo(typeRoot) + .implicitFrom(typeRoot) + .build(); + } + + // cast specification + + castTo(CHAR) + .implicitFrom(CHAR) + .explicitFromFamily(PREDEFINED) + .explicitNotFromFamily(BINARY_STRING) + .build(); + + castTo(VARCHAR) + .implicitFromFamily(CHARACTER_STRING) + .explicitFromFamily(PREDEFINED) + .explicitNotFromFamily(BINARY_STRING) + .build(); + + castTo(BOOLEAN) + .implicitFrom(BOOLEAN) + .explicitFromFamily(CHARACTER_STRING) + .build(); + + castTo(BINARY) + .implicitFromFamily(BINARY_STRING) + .build(); + + castTo(VARBINARY) + .implicitFromFamily(BINARY_STRING) + .build(); + + castTo(DECIMAL) + .implicitFromFamily(NUMERIC) + .explicitFromFamily(CHARACTER_STRING) + .build(); + + castTo(TINYINT) + .implicitFrom(TINYINT) + .explicitFromFamily(NUMERIC, CHARACTER_STRING) + .build(); + + castTo(SMALLINT) + .implicitFrom(TINYINT, SMALLINT) + .explicitFromFamily(NUMERIC, CHARACTER_STRING) + .build(); + + castTo(INTEGER) + .implicitFrom(TINYINT, SMALLINT, INTEGER) + .explicitFromFamily(NUMERIC, CHARACTER_STRING) + .build(); + + castTo(BIGINT) + .implicitFrom(TINYINT, SMALLINT, INTEGER, BIGINT) + .explicitFromFamily(NUMERIC, CHARACTER_STRING) + .build(); + + castTo(FLOAT) + .implicitFrom(TINYINT, SMALLINT, INTEGER, BIGINT, FLOAT, DECIMAL) + .explicitFromFamily(NUMERIC, CHARACTER_STRING) + .build(); + + castTo(DOUBLE) + .implicitFrom(TINYINT, SMALLINT, INTEGER, BIGINT, FLOAT, DOUBLE, DECIMAL) + .explicitFromFamily(CHARACTER_STRING) + .build(); + + castTo(DATE) + .implicitFrom(DATE, TIMESTAMP_WITHOUT_TIME_ZONE) + .explicitFromFamily(TIMESTAMP, CHARACTER_STRING) + .build(); + + castTo(TIME_WITHOUT_TIME_ZONE) + .implicitFrom(TIME_WITHOUT_TIME_ZONE, TIMESTAMP_WITHOUT_TIME_ZONE) + .explicitFromFamily(TIME, TIMESTAMP, CHARACTER_STRING) + .build(); + + castTo(TIMESTAMP_WITHOUT_TIME_ZONE) + .implicitFrom(TIMESTAMP_WITHOUT_TIME_ZONE) + .explicitFromFamily(DATETIME, CHARACTER_STRING) + .build(); + + castTo(TIMESTAMP_WITH_TIME_ZONE) + .implicitFrom(TIMESTAMP_WITH_TIME_ZONE) + .explicitFromFamily(DATETIME, CHARACTER_STRING) + .build(); + + castTo(TIMESTAMP_WITH_LOCAL_TIME_ZONE) + .implicitFrom(TIMESTAMP_WITH_LOCAL_TIME_ZONE) + .explicitFromFamily(DATETIME, CHARACTER_STRING) + .build(); + + castTo(INTERVAL_YEAR_MONTH) + .implicitFrom(INTERVAL_YEAR_MONTH) + .explicitFromFamily(EXACT_NUMERIC, CHARACTER_STRING) + .build(); + + castTo(INTERVAL_DAY_TIME) + .implicitFrom(INTERVAL_DAY_TIME) + .explicitFromFamily(EXACT_NUMERIC, CHARACTER_STRING) + .build(); + } + + public static boolean supportsImplicitCast(LogicalType sourceType, LogicalType targetType) { + return supportsCasting(sourceType, targetType, false); + } + + public static boolean supportsExplicitCast(LogicalType sourceType, LogicalType targetType) { + return supportsCasting(sourceType, targetType, true); + } + + // -------------------------------------------------------------------------------------------- + + private static boolean supportsCasting( + LogicalType sourceType, + LogicalType targetType, + boolean allowExplicit) { + if (sourceType.isNullable() && !targetType.isNullable()) { + return false; + } + // ignore nullability during compare + if (sourceType.copy(true).equals(targetType.copy(true))) { + return true; + } + + final LogicalTypeRoot sourceRoot = sourceType.getTypeRoot(); + final LogicalTypeRoot targetRoot = targetType.getTypeRoot(); + + if (hasFamily(sourceType, INTERVAL) && hasFamily(targetType, EXACT_NUMERIC)) { + // cast between interval and exact numeric is only supported if interval has a single field + return isSingleFieldInterval(sourceType); + } else if (hasFamily(sourceType, EXACT_NUMERIC) && hasFamily(targetType, INTERVAL)) { + // cast between interval and exact numeric is only supported if interval has a single field + return isSingleFieldInterval(targetType); + } else if (hasFamily(sourceType, CONSTRUCTED) || hasFamily(targetType, CONSTRUCTED)) { + return supportsConstructedCasting(sourceType, targetType, allowExplicit); + } else if (sourceRoot == DISTINCT_TYPE && targetRoot == DISTINCT_TYPE) { + // the two distinct types are not equal (from initial invariant), casting is not possible + return false; + } else if (sourceRoot == DISTINCT_TYPE) { + return supportsCasting(((DistinctType) sourceType).getSourceType(), targetType, allowExplicit); + } else if (targetRoot == DISTINCT_TYPE) { + return supportsCasting(sourceType, ((DistinctType) targetType).getSourceType(), allowExplicit); + } else if (sourceRoot == STRUCTURED_TYPE || targetRoot == STRUCTURED_TYPE) { + // TODO structured types are not supported yet + return false; + } else if (sourceRoot == NULL) { + // null can be cast to an arbitrary type + return true; + } else if (sourceRoot == ANY || targetRoot == ANY) { + // the two any types are not equal (from initial invariant), casting is not possible + return false; + } else if (sourceRoot == SYMBOL || targetRoot == SYMBOL) { + // the two symbol types are not equal (from initial invariant), casting is not possible + return false; + } + + if (implicitCastingRules.get(targetRoot).contains(sourceRoot)) { + return true; + } + if (allowExplicit) { + return explicitCastingRules.get(targetRoot).contains(sourceRoot); + } + return false; + } + + private static boolean supportsConstructedCasting( + LogicalType sourceType, + LogicalType targetType, + boolean allowExplicit) { + final LogicalTypeRoot sourceRoot = sourceType.getTypeRoot(); + final LogicalTypeRoot targetRoot = targetType.getTypeRoot(); + // all constructed types can only be casted within the same type root + if (sourceRoot == targetRoot) { + final List<LogicalType> sourceChildren = sourceType.getChildren(); + final List<LogicalType> targetChildren = targetType.getChildren(); + if (sourceChildren.size() != targetChildren.size()) { + return false; + } + for (int i = 0; i < sourceChildren.size(); i++) { + if (!supportsCasting(sourceChildren.get(i), targetChildren.get(i), allowExplicit)) { + return false; + } + } + return true; + } + return false; + } + + private static CastingRuleBuilder castTo(LogicalTypeRoot sourceType) { + return new CastingRuleBuilder(sourceType); + } + + private static LogicalTypeRoot[] allTypes() { + return LogicalTypeRoot.values(); + } + + private static class CastingRuleBuilder { + + private final LogicalTypeRoot sourceType; Review comment: I am not sure about this, but shouldn't the names be inverted? Shouldn't `sourceType` -> `targetType` & `implicit/explicitTargetTypes` -> `implicit/explicitSourceTypes` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
