[SPARK-57544][SQL] Rework column ID validation for nested fields in DSv2

common/utils/src/main/resources/error/error-conditions.json

@@ -2931,12 +2931,6 @@
           "<errors>"
         ]
       },
-      "COLUMN_ID_MISMATCH" : {
-        "message" : [
-          "Column IDs have changed:",
-          "<errors>"
-        ]
-      },
       "METADATA_COLUMNS_MISMATCH" : {
         "message" : [
           "Metadata columns have changed:",

sql/api/src/main/scala/org/apache/spark/sql/catalyst/util/FieldMetadataUtils.scala

@@ -0,0 +1,23 @@
+/*
+ * 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.util
+
+object FieldMetadataUtils {
+  // Metadata key for the field ID used to track column identity across schema evolution
+  val FIELD_ID_METADATA_KEY = "__FIELD_ID"
+}

sql/api/src/main/scala/org/apache/spark/sql/types/StructField.scala

@@ -26,6 +26,7 @@ import org.json4s.JsonDSL._
 import org.apache.spark.SparkException
 import org.apache.spark.annotation.Stable
 import org.apache.spark.sql.catalyst.util.{CollationFactory, QuotingUtils, StringConcat}
+import org.apache.spark.sql.catalyst.util.FieldMetadataUtils.FIELD_ID_METADATA_KEY
 import org.apache.spark.sql.catalyst.util.ResolveDefaultColumnsUtils.{CURRENT_DEFAULT_COLUMN_METADATA_KEY, EXISTS_DEFAULT_COLUMN_METADATA_KEY}
 import org.apache.spark.util.SparkSchemaUtils
 
@@ -243,6 +244,43 @@ case class StructField(
     metadata.contains(EXISTS_DEFAULT_COLUMN_METADATA_KEY)
   }
 
+  /**
+   * Updates the field with an ID for column identity tracking.
+   */
+  def withId(id: String): StructField = {
+    val newMetadata = new MetadataBuilder()
+      .withMetadata(metadata)
+      .putString(FIELD_ID_METADATA_KEY, id)
+      .build()
+    copy(metadata = newMetadata)
+  }
+
+  /**
+   * Returns the ID of this field, if set.
+   */
+  def id: Option[String] = {
+    if (metadata.contains(FIELD_ID_METADATA_KEY)) {
+      Some(metadata.getString(FIELD_ID_METADATA_KEY))
+    } else {
+      None
+    }
+  }
+
+  /**
+   * Returns a copy of this field with the field ID removed, or this field if no ID is set.
+   */
+  def clearId(): StructField = {
+    if (metadata.contains(FIELD_ID_METADATA_KEY)) {
+      val newMetadata = new MetadataBuilder()
+        .withMetadata(metadata)
+        .remove(FIELD_ID_METADATA_KEY)
+        .build()
+      copy(metadata = newMetadata)
+    } else {
+      this
+    }
+  }
+
   private def getDDLDefault = getDefault()
     .orElse(getCurrentDefaultValue())
     .map(" DEFAULT " + _)

sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/Column.java

@@ -18,12 +18,17 @@
 package org.apache.spark.sql.connector.catalog;
 
 import java.util.Map;
+import java.util.Objects;
+import java.util.stream.Stream;
 import javax.annotation.Nullable;
 
+import org.apache.spark.SparkIllegalArgumentException;
 import org.apache.spark.annotation.Evolving;
 import org.apache.spark.sql.connector.expressions.Transform;
 import org.apache.spark.sql.internal.connector.ColumnImpl;
 import org.apache.spark.sql.types.DataType;
+import org.apache.spark.sql.types.StructField;
+import org.apache.spark.sql.util.SchemaUtils;
 
 /**
  * An interface representing a column of a {@link Table}. It defines basic properties of a column,
@@ -40,11 +45,11 @@
 public interface Column {
 
   static Column create(String name, DataType dataType) {
-    return create(name, dataType, true);
+    return builderFor(name, dataType).build();
   }
 
   static Column create(String name, DataType dataType, boolean nullable) {
-    return create(name, dataType, nullable, null, null);
+    return builderFor(name, dataType).nullable(nullable).build();
   }
 
   static Column create(
@@ -53,16 +58,11 @@ static Column create(
       boolean nullable,
       String comment,
       String metadataInJSON) {
-    return new ColumnImpl(
-        name,
-        dataType,
-        nullable,
-        comment,
-        /* defaultValue = */ null,
-        /* generationExpression = */ null,
-        /* identityColumnSpec = */ null,
-        metadataInJSON,
-        /* id = */ null);
+    return builderFor(name, dataType)
+        .nullable(nullable)
+        .comment(comment)
+        .metadata(metadataInJSON)
+        .build();
   }
 
   static Column create(
@@ -72,16 +72,12 @@ static Column create(
       String comment,
       ColumnDefaultValue defaultValue,
       String metadataInJSON) {
-    return new ColumnImpl(
-        name,
-        dataType,
-        nullable,
-        comment,
-        defaultValue,
-        /* generationExpression = */ null,
-        /* identityColumnSpec = */ null,
-        metadataInJSON,
-        /* id = */ null);
+    return builderFor(name, dataType)
+        .nullable(nullable)
+        .comment(comment)
+        .defaultValue(defaultValue)
+        .metadata(metadataInJSON)
+        .build();
   }
 
   static Column create(
@@ -91,35 +87,57 @@ static Column create(
       String comment,
       String generationExpression,
       String metadataInJSON) {
-    return new ColumnImpl(
-        name,
-        dataType,
-        nullable,
-        comment,
-        /* defaultValue = */ null,
-        generationExpression,
-        /* identityColumnSpec = */ null,
-        metadataInJSON,
-        /* id = */ null);
+    return builderFor(name, dataType)
+        .nullable(nullable)
+        .comment(comment)
+        .generationExpression(generationExpression)
+        .metadata(metadataInJSON)
+        .build();
   }
 
   static Column create(
-          String name,
-          DataType dataType,
-          boolean nullable,
-          String comment,
-          IdentityColumnSpec identityColumnSpec,
-          String metadataInJSON) {
-    return new ColumnImpl(
-        name,
-        dataType,
-        nullable,
-        comment,
-        /* defaultValue = */ null,
-        /* generationExpression = */ null,
-        identityColumnSpec,
-        metadataInJSON,
-        /* id = */ null);
+      String name,
+      DataType dataType,
+      boolean nullable,
+      String comment,
+      IdentityColumnSpec identityColumnSpec,
+      String metadataInJSON) {
+    return builderFor(name, dataType)
+        .nullable(nullable)
+        .comment(comment)
+        .identityColumnSpec(identityColumnSpec)
+        .metadata(metadataInJSON)
+        .build();
+  }
+
+  /**
+   * Creates a builder for a new column with the given name and data type.
+   *
+   * @param name the name of the column
+   * @param dataType the data type of the column
+   * @return a new builder
+   * @since 4.2.0
+   */
+  static Builder builderFor(String name, DataType dataType) {
+    return new Builder(name, dataType);
+  }
+
+  /**
+   * Creates a builder with pre-populated info from an existing column.
+   *
+   * @param column the source column
+   * @return a new builder seeded with the column's current state
+   * @since 4.2.0
+   */
+  static Builder builderFrom(Column column) {
+    return new Builder(column.name(), column.dataType())
+        .nullable(column.nullable())
+        .comment(column.comment())
+        .defaultValue(column.defaultValue())
+        .generationExpression(column.generationExpression())
+        .identityColumnSpec(column.identityColumnSpec())
+        .metadata(column.metadataInJSON())
+        .id(column.id());
   }
 
   /**
@@ -193,12 +211,99 @@ static Column create(
    * others.
    * <p>
    * This API covers top-level columns only. Nested struct fields, array elements, and map
-   * keys/values do not have separate IDs. Connectors that track nested field IDs can encode
-   * them into the returned top-level Column ID string to detect nested changes, since Spark
-   * only compares string equality.
+   * keys/values carry their own IDs in struct field metadata. Spark validates both top-level and
+   * nested struct field IDs as part of schema compatibility checks (array elements and map/key
+   * values' validation is not supported yet). See {@link StructField#id()}.
    */
   @Nullable
   default String id() {
     return null;
   }
+
+  /**
+   * A builder for {@link Column}.
+   *
+   * @since 4.2.0
+   */
+  class Builder {
+    private final String name;
+    private DataType dataType;
+    private boolean nullable = true;
+    private String comment = null;
+    private ColumnDefaultValue defaultValue = null;
+    private String genExpr = null;
+    private IdentityColumnSpec identityColumnSpec = null;
+    private String metadataInJSON = null;
+    private String id = null;
+
+    private Builder(String name, DataType dataType) {
+      this.name = Objects.requireNonNull(name, "name must not be null");
+      this.dataType = Objects.requireNonNull(dataType, "dataType must not be null");
+    }
+
+    public Builder nullable(boolean nullable) {
+      this.nullable = nullable;
+      return this;
+    }
+
+    public Builder comment(String comment) {
+      this.comment = comment;
+      return this;
+    }
+
+    public Builder defaultValue(ColumnDefaultValue defaultValue) {
+      this.defaultValue = defaultValue;
+      return this;
+    }
+
+    public Builder generationExpression(String sql) {
+      this.genExpr = sql;
+      return this;
+    }
+
+    public Builder identityColumnSpec(IdentityColumnSpec identityColumnSpec) {
+      this.identityColumnSpec = identityColumnSpec;
+      return this;
+    }
+
+    public Builder metadata(String metadataInJSON) {
+      this.metadataInJSON = metadataInJSON;
+      return this;
+    }
+
+    public Builder id(String id) {
+      this.id = id;
+      return this;
+    }
+
+    public Builder clearIds() {
+      this.id = null;
+      this.dataType = SchemaUtils.clearFieldIds(dataType);
+      return this;
+    }
+
+    public Column build() {
+      validateState();
+      return new ColumnImpl(
+          name, dataType, nullable, comment, defaultValue,
+          genExpr, identityColumnSpec, metadataInJSON, id);
+    }
+
+    private void validateState() {
+      if (hasConflictingDefinitions()) {
+        throw new SparkIllegalArgumentException(
+            "INTERNAL_ERROR",
+            Map.of("message",
+                "Column '" + name + "' cannot have more than one definition of: " +
+                "default value, generation expression, identity column spec"));
+      }
+    }
+
+    private boolean hasConflictingDefinitions() {
+      long definitionCount = Stream.of(defaultValue, genExpr, identityColumnSpec)
+          .filter(Objects::nonNull)
+          .count();
+      return definitionCount > 1;
+    }
+  }
 }

sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/RelationBuilder.java

@@ -44,7 +44,7 @@ public B withColumns(Column[] columns) {
   }
 
   public B withSchema(StructType schema) {
-    this.columns = CatalogV2Util.structTypeToV2Columns(schema);
+    this.columns = CatalogV2Util.structTypeToV2Columns(schema, true /* keep IDs */);
     return self();
   }
 

sql/catalyst/src/main/java/org/apache/spark/sql/connector/catalog/Table.java

@@ -78,7 +78,7 @@ default StructType schema() {
    * empty array can be returned here.
    */
   default Column[] columns() {
-    return CatalogV2Util.structTypeToV2Columns(schema());
+    return CatalogV2Util.structTypeToV2Columns(schema(), true /* keep IDs */);
   }
 
   /**