dtenedor commented on a change in pull request #35855: URL: https://github.com/apache/spark/pull/35855#discussion_r827571422
########## File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/DefaultColumns.scala ########## @@ -0,0 +1,266 @@ +/* + * 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.spark.sql.catalyst.analysis + +import org.apache.spark.sql.AnalysisException +import org.apache.spark.sql.catalyst.TableIdentifier +import org.apache.spark.sql.catalyst.catalog._ +import org.apache.spark.sql.catalyst.expressions.{Expression, _} +import org.apache.spark.sql.catalyst.optimizer.ConstantFolding +import org.apache.spark.sql.catalyst.parser.{CatalystSqlParser, ParseException} +import org.apache.spark.sql.catalyst.plans.logical._ +import org.apache.spark.sql.types._ + +/** + * This class contains logic for processing DEFAULT columns in statements such as CREATE TABLE. + */ +object DefaultColumns { + val default = "default" + val analysisPrefix = + " has a DEFAULT value which fails to resolve to a valid constant expression: " + val columnDefaultNotFound = "Column 'default' does not exist" + lazy val parser = new CatalystSqlParser() + lazy val analyzer = + new Analyzer(new SessionCatalog(new InMemoryCatalog, FunctionRegistry.builtin)) + + /** + * Finds DEFAULT expressions in CREATE/REPLACE TABLE commands and constant-folds then. + * + * Example: + * CREATE TABLE T(a INT, b INT DEFAULT 5 + 5) becomes + * CREATE TABLE T(a INT, b INT DEFAULT 10) + * + * @param tableSchema represents the names and types of the columns of the statement to process. + * @param statementType name of the statement being processed, such as INSERT; useful for errors. + * @return a copy of `tableSchema` with field metadata updated with the constant-folded values. + */ + def ConstantFoldDefaultExpressions(tableSchema: StructType, statementType: String): StructType = { + // Get the list of column indexes in the CREATE TABLE command with DEFAULT values. + val (fields: Array[StructField], indexes: Array[Int]) = + tableSchema.fields.zipWithIndex.filter { case (f, i) => f.metadata.contains(default) }.unzip + // Extract the list of DEFAULT column values from the CreateTable command. + val colNames: Seq[String] = fields.map { _.name } + val defaults: Seq[String] = fields.map { _.metadata.getString(default) } + // Extract the list of DEFAULT column values from the CreateTable command. + val exprs: Seq[Expression] = colNames.zip(defaults).map { + case (name, text) => Parse(name, text, statementType) + } + // Analyze and constant-fold each parse result. + val analyzed: Seq[Expression] = (exprs, defaults, colNames).zipped.map { + case (expr, default, name) => Analyze(expr, default, name, statementType) + } + // Create a map from the column index of each DEFAULT column to its type. + val indexMap: Map[Int, StructField] = (indexes, fields, analyzed).zipped.map { + case (index, field, expr) => + val newMetadata: Metadata = new MetadataBuilder().withMetadata(field.metadata) + .putString(default, expr.sql).build() + (index, field.copy(metadata = newMetadata)) + }.toMap + // Finally, replace the original struct fields with the new ones. + val newFields: Seq[StructField] = + tableSchema.fields.zipWithIndex.map { case (f, i) => indexMap.getOrElse(i, f) } + StructType(newFields) + } + + /** + * Parses DEFAULT column text to an expression, returning a reasonable error upon failure. + * + * @param colName the name of the DEFAULT column whose text we endeavor to parse. + * @param colText the string contents of the DEFAULT column value. + * @param statementType which type of statement we are running, such as INSERT; useful for errors. + * @return the expression resulting from the parsing step. + */ + private def Parse(colName: String, colText: String, statementType: String): Expression = { + try { + parser.parseExpression(colText) + } catch { + case ex: ParseException => + throw new AnalysisException( + s"Failed to execute $statementType command because the destination table column " + + colName + analysisPrefix + s"$colText yields ${ex.getMessage}") + } + } + + /** + * Analyzes and constant-folds `colExpr`, returning a reasonable error message upon failure. + * + * @param colExpr result of a parsing operation suitable for consumption by analysis. + * @param colText string contents of the DEFAULT column value; useful for errors. + * @param colName string name of the DEFAULT column; useful for errors. + * @param statementType which type of statement we are running, such as INSERT; useful for errors. + * @return Result of the analysis and constant-folding operation. + */ + private def Analyze(colExpr: Expression, colText: String, colName: String, + statementType: String): Expression = { + try { + // Invoke the analyzer over the 'colExpr'. + val plan = analyzer.execute(Project(Seq(Alias(colExpr, colName)()), OneRowRelation())) + analyzer.checkAnalysis(plan) + // Perform constant folding over the result. + val folded = ConstantFolding(plan) + val result = folded match { + case Project(Seq(a: Alias), OneRowRelation()) => a.child + } + // Make sure the constant folding was successful. + result match { + case _: Literal => result + case _ => throw new AnalysisException("non-constant value") + } + } catch { + case ex: AnalysisException => + throw new AnalysisException( + s"Failed to execute $statementType command because the destination table column " + + colName + analysisPrefix + s"$colText yields ${ex.getMessage}") + } + } + + /** + * Replaces unresolved "DEFAULT" column references with matching default column values. + * + * Background: CREATE TABLE and ALTER TABLE invocations support setting column default values for + * later operations. Following INSERT, and INSERT MERGE commands may then reference the value + * using the DEFAULT keyword as needed. + * + * Example: + * CREATE TABLE T(a INT DEFAULT 4, b INT NOT NULL DEFAULT 5); + * INSERT INTO T VALUES (1, 2); + * INSERT INTO T VALUES (1, DEFAULT); + * INSERT INTO T VALUES (DEFAULT, 6); + * SELECT * FROM T; + * (1, 2) + * (1, 5) + * (4, 6) + * + * @param insert the INSERT INTO statement to replace explicit DEFAULT column references within. + * @param catalog session catalog for use when looking up table names for the statement. + * @return the updated statement with DEFAULT column references replaced with their values. + */ + def ReplaceExplicitDefaultColumnValues(insert: InsertIntoStatement, + catalog: SessionCatalog): InsertIntoStatement = { Review comment: Done. -- 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. 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