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_r297550452
########## 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; + private Set<LogicalTypeRoot> implicitTargetTypes = new HashSet<>(); + private Set<LogicalTypeRoot> explicitTargetTypes = new HashSet<>(); + + CastingRuleBuilder(LogicalTypeRoot sourceType) { + this.sourceType = sourceType; + } + + CastingRuleBuilder implicitFrom(LogicalTypeRoot... targetTypes) { + this.implicitTargetTypes.addAll(Arrays.asList(targetTypes)); + return this; + } + + CastingRuleBuilder implicitFromFamily(LogicalTypeFamily... targetFamilies) { + for (LogicalTypeFamily family : targetFamilies) { + for (LogicalTypeRoot root : LogicalTypeRoot.values()) { + if (root.getFamilies().contains(family)) { + this.implicitTargetTypes.add(root); + } + } + } + return this; + } + + CastingRuleBuilder explicitFrom(LogicalTypeRoot... targetTypes) { + this.explicitTargetTypes.addAll(Arrays.asList(targetTypes)); + return this; + } + + CastingRuleBuilder explicitFromFamily(LogicalTypeFamily... targetFamilies) { + for (LogicalTypeFamily family : targetFamilies) { + for (LogicalTypeRoot root : LogicalTypeRoot.values()) { + if (root.getFamilies().contains(family)) { + this.explicitTargetTypes.add(root); + } + } + } + return this; + } + + CastingRuleBuilder explicitNotFromFamily(LogicalTypeFamily... targetFamilies) { Review comment: Could we add a comment that this should be defined/used last? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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