[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 ifExpr: If => | ||
| ifExpr.withNewChildren( | ||
| ifExpr.predicate +: collateToSingleType(Seq(ifExpr.trueValue, ifExpr.falseValue))) | ||
| case caseWhenExpr: CaseWhen => | ||
| val newValues = collateToSingleType( | ||
| caseWhenExpr.branches.map(b => b._2) ++ caseWhenExpr.elseValue) | ||
| caseWhenExpr.withNewChildren( | ||
| interleave(Seq.empty, caseWhenExpr.branches.map(b => b._1), newValues)) | ||
| case substrExpr: Substring => | ||
| // This case is necessary for changing Substring input to implicit collation | ||
| substrExpr.withNewChildren( | ||
| collateToSingleType(Seq(substrExpr.str)) :+ substrExpr.pos :+ substrExpr.len) | ||
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There was a problem hiding this comment. I don't get it. Why do we find the common collation for a single type? There was a problem hiding this comment. For now we do not need it, I can revert this change and leave it for default collation handling. Because if we add a flag for collation priority, we will need to change the priority of the input to implicit, if it was default before. |
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| case otherExpr @ ( | ||
| _: In | _: InSubquery | _: CreateArray | _: ArrayJoin | _: Concat | _: Greatest | _: Least | | ||
| _: Coalesce | _: BinaryExpression | _: ConcatWs) => | ||
| val newChildren = collateToSingleType(otherExpr.children) | ||
| otherExpr.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 (implicitTypes.length > 1) { | ||
| throw QueryCompilationErrors.implicitCollationMismatchError() | ||
| } | ||
| else { | ||
| implicitTypes.headOption.getOrElse(SQLConf.get.defaultStringType) | ||
| } | ||
| } | ||
| } | ||
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| @tailrec | ||
| final def interleave[A](base: Seq[A], a: Seq[A], b: Seq[A]): Seq[A] = a match { | ||
| case elt :: aTail => interleave(base :+ elt, b, aTail) | ||
| case _ => base ++ b | ||
| } | ||
| } | ||
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The code looks a bit complicated now. Can we follow the existing rule?
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Actually this exposes some gaps in this new rule
!haveSameType(...)castIfNotSameTypeThere was a problem hiding this comment.
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We actually do not blindly Cast in CollationTypeCasts. We only cast if we get different collations, as all other cases go to null branch in castStringType. Maybe it is better to keep this check internal to this rule, as we will add the priority flag and we will need to handle casting of priority in this rule as well later. Am adding the haveSameType for now to make it check the input types, but will change this code in the following PR to include priorities in the internal implementation of haveSameType check.