[GitHub] [spark] cloud-fan commented on a diff in pull request #40308: [SPARK-42151][SQL] Align UPDATE assignments with table attributes

["cloud-fan (via GitHub)" <gi...@apache.org>]

cloud-fan commented on code in PR #40308:
URL: https://github.com/apache/spark/pull/40308#discussion_r1161840413


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/AssignmentUtils.scala:
##########
@@ -0,0 +1,204 @@
+/*
+ * 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 scala.collection.mutable
+
+import org.apache.spark.sql.AnalysisException
+import org.apache.spark.sql.catalyst.SQLConfHelper
+import org.apache.spark.sql.catalyst.expressions.{Attribute, AttributeReference, CreateNamedStruct, Expression, GetArrayItem, GetArrayStructFields, GetMapValue, GetStructField, Literal, NamedExpression}
+import org.apache.spark.sql.catalyst.plans.logical.Assignment
+import org.apache.spark.sql.catalyst.util.CharVarcharUtils
+import org.apache.spark.sql.connector.catalog.CatalogV2Implicits._
+import org.apache.spark.sql.errors.QueryCompilationErrors
+import org.apache.spark.sql.types.{DataType, StructType}
+
+object AssignmentUtils extends SQLConfHelper with CastSupport {
+
+  private case class ColumnUpdate(ref: Seq[String], expr: Expression)
+
+  /**
+   * Aligns assignments to match table columns.
+   * <p>
+   * This method processes and reorders given assignments so that each target column gets
+   * an expression it should be set to. If a column does not have a matching assignment,
+   * it will be set to its current value. For example, if one passes table attributes c1, c2
+   * and an assignment c2 = 1, this method will return c1 = c1, c2 = 1. This alignment is
+   * required to construct an updated version of a row.
+   * <p>
+   * This method also handles updates to nested columns. If there is an assignment to a particular
+   * nested field, this method will construct a new struct with one field updated preserving other
+   * fields that have not been modified. For example, if one passes table attributes c1, c2
+   * where c2 is a struct with fields n1 and n2 and an assignment c2.n2 = 1, this method will
+   * return c1 = c1, c2 = struct(c2.n1, 1).
+   *
+   * @param attrs table attributes
+   * @param assignments assignments to align
+   * @return aligned assignments that match table attributes
+   */
+  def alignAssignments(
+      attrs: Seq[Attribute],
+      assignments: Seq[Assignment]): Seq[Assignment] = {
+
+    val errors = new mutable.ArrayBuffer[String]()
+
+    val output = applyUpdates(
+      updates = assignments.map(toColumnUpdate),
+      cols = attrs.map(restoreActualType),
+      colExprs = attrs,
+      addError = err => errors += err)
+
+    if (errors.nonEmpty) {
+      throw QueryCompilationErrors.invalidRowLevelOperationAssignments(assignments, errors.toSeq)
+    }
+
+    attrs.zip(output).map { case (attr, expr) => Assignment(attr, expr) }
+  }
+
+  private def toColumnUpdate(assignment: Assignment): ColumnUpdate = {
+    ColumnUpdate(toRef(assignment.key), assignment.value)
+  }
+
+  private def restoreActualType(attr: Attribute): Attribute = {
+    attr.withDataType(CharVarcharUtils.getRawType(attr.metadata).getOrElse(attr.dataType))
+  }
+
+  private def applyUpdates(

Review Comment:
   A few ideas to make the code more robust:
   1. I think it's better to operate on the resolved column expressions, instead of turning back the expression to `Seq[String]`
   2. Given the parser rule for the UPDATE command, the column expression can only be `AttributeReference` or accessing (array of) struct's fields. We can group by `expr.references.head` to get a map from `AttributeReference` to `Seq[Expression]` and the corresponding update expressions.
   3. We validate the map we got in step 2: for each top-level column, its expressions must be of the same tree height (to avoid updating both 'a.b' and 'a.b.c'), and must be different from each other.
   4. Now it's easy to build the new update expressions: for each top-level column, if it doesn't have a match in the map, use the actual column value as the update expression, else ... (same algorithm below)



-- 
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.

To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org


---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org