[SPARK-47210][SQL] Addition of implicit casting without indeterminate support #45383
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| layout: global | ||
| title: COLLATION_MISMATCH error class | ||
| displayTitle: COLLATION_MISMATCH error class | ||
| license: | | ||
| 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 | ||
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| http://www.apache.org/licenses/LICENSE-2.0 | ||
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| 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. | ||
| --- | ||
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| <!-- | ||
| DO NOT EDIT THIS FILE. | ||
| It was generated automatically by `org.apache.spark.SparkThrowableSuite`. | ||
| --> | ||
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| [SQLSTATE: 42P21](sql-error-conditions-sqlstates.html#class-42-syntax-error-or-access-rule-violation) | ||
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| Could not determine which collation to use for string functions and operators. | ||
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| This error class has the following derived error classes: | ||
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| ## EXPLICIT | ||
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| Error occurred due to the mismatch between explicit collations: `<explicitTypes>`. Decide on a single explicit collation and remove others. | ||
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| ## IMPLICIT | ||
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| Error occurred due to the mismatch between multiple implicit non-default collations. Use COLLATE function to set the collation explicitly. | ||
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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. | ||
| */ | ||
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| package org.apache.spark.sql.catalyst.analysis | ||
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| import javax.annotation.Nullable | ||
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| import scala.annotation.tailrec | ||
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| import org.apache.spark.sql.catalyst.analysis.TypeCoercion.{hasStringType} | ||
| import org.apache.spark.sql.catalyst.expressions.{ArrayJoin, BinaryExpression, CaseWhen, Cast, Coalesce, Collate, Concat, ConcatWs, CreateArray, Expression, Greatest, If, In, InSubquery, Least, Substring} | ||
| import org.apache.spark.sql.errors.QueryCompilationErrors | ||
| import org.apache.spark.sql.internal.SQLConf | ||
| import org.apache.spark.sql.types.{AbstractDataType, ArrayType, DataType, StringType} | ||
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| object CollationTypeCasts extends TypeCoercionRule { | ||
| override val transform: PartialFunction[Expression, Expression] = { | ||
| case e if !e.childrenResolved => e | ||
| case sc@(_: In | ||
| | _: InSubquery | ||
| | _: CreateArray | ||
| | _: If | ||
| | _: ArrayJoin | ||
| | _: CaseWhen | ||
| | _: Concat | ||
| | _: Greatest | ||
| | _: Least | ||
| | _: Coalesce | ||
| | _: BinaryExpression | ||
| | _: ConcatWs | ||
| | _: Substring) => | ||
| val newChildren = collateToSingleType(sc.children) | ||
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There was a problem hiding this comment. This is the tricky part of adding a new rule. We must make sure we follow the behavior of existing implicit cast rules and only add implicit cast for certain children of an expression. For example, the true and false branches of Please carefully check all implicit cast rules and revisit this new rule. @mihailom-db There was a problem hiding this comment. This rule is only touching children that have StringType's as their DataType. I can reorder execution to first filter out StringType arguments and then work on them, Agreed for There was a problem hiding this comment. Let's not assume thar it's safe to only cast string-type inputs for any expression. Please follow the existing implicit cast rules and explicitly match expressions that need some of their inputs to be the same type. There was a problem hiding this comment. This is the problem. If I understood correctly, we do not want to replicate the code from ImplicitTypeCasts. This rule is concerned with transforming datatypes into their expected DataTypes, but CollationTypeCasts is concerned with transforming StringTypes into their expected collated StringType. There is a difference, as collated StringType is calculated based on expression parameters that have StringTypes not on what someone expects the input types to be. As you mentioned for There was a problem hiding this comment.
I don't think this is possible without significant refactoring. Correctness is more important than duplicated code at this stage. |
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| sc.withNewChildren(newChildren) | ||
| } | ||
| /** | ||
| * Extracts StringTypes from filtered hasStringType | ||
| */ | ||
| @tailrec | ||
| private def extractStringType(dt: DataType): StringType = dt match { | ||
| case st: StringType => st | ||
| case ArrayType(et, _) => extractStringType(et) | ||
| } | ||
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| /** | ||
| * Casts given expression to collated StringType with id equal to collationId only | ||
| * if expression has StringType in the first place. | ||
| * @param expr | ||
| * @param collationId | ||
| * @return | ||
| */ | ||
| def castStringType(expr: Expression, st: StringType): Option[Expression] = | ||
| castStringType(expr.dataType, st).map { dt => Cast(expr, dt)} | ||
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| private def castStringType(inType: AbstractDataType, castType: StringType): Option[DataType] = { | ||
| @Nullable val ret: DataType = inType match { | ||
| case st: StringType if st.collationId != castType.collationId => castType | ||
| case ArrayType(arrType, nullable) => | ||
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There was a problem hiding this comment. I disagree with special-case array type. The code looks broken. It assumes the children of the given expression can have both string type and array of string type, then tries to find a common collation between the string type child and the array element. This makes no sense without knowing the semantic of the given expression. There was a problem hiding this comment. A simple example is ConcatWs. It can have ArrayType(StringType, _) for input strings and StringType for separator as parameters. What collations do we want for this then? We need to cast the ArrayType into a proper collation if separator is explicit. There was a problem hiding this comment. Then please match the ConcatWs expression explicitly to handle this case. What I disagree with is to do this blindly for all expressions. |
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| castStringType(arrType, castType).map(ArrayType(_, nullable)).orNull | ||
| case _ => null | ||
| } | ||
| Option(ret) | ||
| } | ||
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| /** | ||
| * Collates input expressions to a single collation. | ||
| */ | ||
| def collateToSingleType(exprs: Seq[Expression]): Seq[Expression] = { | ||
| val st = getOutputCollation(exprs) | ||
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| exprs.map(e => castStringType(e, st).getOrElse(e)) | ||
| } | ||
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| /** | ||
| * Based on the data types of the input expressions this method determines | ||
| * a collation type which the output will have. This function accepts Seq of | ||
| * any expressions, but will only be affected by collated StringTypes or | ||
| * complex DataTypes with collated StringTypes (e.g. ArrayType) | ||
| */ | ||
| def getOutputCollation(expr: Seq[Expression]): StringType = { | ||
| val explicitTypes = expr.filter(_.isInstanceOf[Collate]) | ||
| .map(_.dataType.asInstanceOf[StringType].collationId) | ||
| .distinct | ||
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| explicitTypes.size match { | ||
| // We have 1 explicit collation | ||
| case 1 => StringType(explicitTypes.head) | ||
| // Multiple explicit collations occurred | ||
| case size if size > 1 => | ||
| throw QueryCompilationErrors | ||
| .explicitCollationMismatchError( | ||
| explicitTypes.map(t => StringType(t).typeName) | ||
| ) | ||
| // Only implicit or default collations present | ||
| case 0 => | ||
| val implicitTypes = expr.map(_.dataType) | ||
| .filter(hasStringType) | ||
| .map(extractStringType) | ||
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| .filter(dt => dt.collationId != SQLConf.get.defaultStringType.collationId) | ||
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| .distinctBy(_.collationId) | ||
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| if (hasMultipleImplicits(implicitTypes)) { | ||
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| throw QueryCompilationErrors.implicitCollationMismatchError() | ||
| } | ||
| else { | ||
| implicitTypes.headOption.getOrElse(SQLConf.get.defaultStringType) | ||
| } | ||
| } | ||
| } | ||
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| /** | ||
| * This check is always preformed when we have no explicit collation. It returns true | ||
| * if there are more than one implicit collations. Collations are distinguished by their | ||
| * collationId. | ||
| * @param dataTypes | ||
| * @return | ||
| */ | ||
| private def hasMultipleImplicits(dataTypes: Seq[StringType]): Boolean = | ||
| dataTypes.map(_.collationId) | ||
| .filter(dt => !(dt == SQLConf.get.defaultStringType.collationId)).distinct.size > 1 | ||
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| } | ||
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We should add more case matches as some expressions do not require all its inputs to be the same type