modify syntax

Author: jiangxb1987

sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4

@@ -90,7 +90,7 @@ statement
     | ALTER (TABLE | VIEW) tableIdentifier
         UNSET TBLPROPERTIES (IF EXISTS)? tablePropertyList             #unsetTableProperties
     | ALTER TABLE tableIdentifier partitionSpec?
-        CHANGE COLUMN? expandColTypeList                               #changeColumns
+        CHANGE COLUMN? identifier colType colPosition?                 #changeColumn
     | ALTER TABLE tableIdentifier (partitionSpec)?
         SET SERDE STRING (WITH SERDEPROPERTIES tablePropertyList)?     #setTableSerDe
     | ALTER TABLE tableIdentifier (partitionSpec)?
@@ -598,14 +598,6 @@ colType
     : identifier dataType (COMMENT STRING)?
     ;
 
-expandColTypeList
-    : expandColType (',' expandColType)*
-    ;
-
-expandColType
-    : identifier colType colPosition?
-    ;
-
 complexColTypeList
     : complexColType (',' complexColType)*
     ;

sql/core/src/main/scala/org/apache/spark/sql/execution/SparkSqlParser.scala

@@ -877,32 +877,30 @@ class SparkSqlAstBuilder(conf: SQLConf) extends AstBuilder {
   }
 
   /**
-   * Create a [[AlterTableChangeColumnsCommand]] command.
+   * Create a [[AlterTableChangeColumnCommand]] command.
    *
    * For example:
    * {{{
    *   ALTER TABLE table [PARTITION partition_spec]
-   *   CHANGE [COLUMN] `col` `col` dataType [COMMENT "comment"] [FIRST | AFTER `otherCol`]
-   *   [, `col2` `col2` dataType [COMMENT "comment"] [FIRST | AFTER `otherCol`], ...]
+   *   CHANGE [COLUMN] column_old_name column_new_name column_dataType [COMMENT column_comment]
+   *   [FIRST | AFTER column_name];
    * }}}
    */
-  override def visitChangeColumns(ctx: ChangeColumnsContext): LogicalPlan = withOrigin(ctx) {
+  override def visitChangeColumn(ctx: ChangeColumnContext): LogicalPlan = withOrigin(ctx) {
     if (ctx.partitionSpec != null) {
       operationNotAllowed("ALTER TABLE table PARTITION partition_spec CHANGE COLUMN", ctx)
     }
 
-    val tableName = visitTableIdentifier(ctx.tableIdentifier)
-
-    val columns = ctx.expandColTypeList.expandColType.asScala.map { col =>
-      if (col.colPosition != null) {
-        operationNotAllowed(
-          "ALTER TABLE table [PARTITION partition_spec] CHANGE COLUMN ... FIRST | AFTER otherCol",
-          ctx)
-      }
-      col.identifier.getText -> visitColType(col.colType)
-    }.toMap
+    if (ctx.colPosition != null) {
+      operationNotAllowed(
+        "ALTER TABLE table [PARTITION partition_spec] CHANGE COLUMN ... FIRST | AFTER otherCol",
+        ctx)
+    }
 
-    AlterTableChangeColumnsCommand(tableName, columns)
+    AlterTableChangeColumnCommand(
+      tableName = visitTableIdentifier(ctx.tableIdentifier),
+      columnName = ctx.identifier.getText,
+      newColumn = visitColType(ctx.colType))
   }
 
   /**

sql/core/src/main/scala/org/apache/spark/sql/execution/command/ddl.scala

@@ -276,8 +276,8 @@ case class AlterTableUnsetPropertiesCommand(
 
 
 /**
- * A command to change the columns for a table, only support changing the comments of non-partition
- * columns for now.
+ * A command to change the column for a table, only support changing the comment of a non-partition
+ * column for now.
  *
  * The syntax of using this command in SQL is:
  * {{{
@@ -286,9 +286,10 @@ case class AlterTableUnsetPropertiesCommand(
  *   [FIRST | AFTER column_name];
  * }}}
  */
-case class AlterTableChangeColumnsCommand(
+case class AlterTableChangeColumnCommand(
     tableName: TableIdentifier,
-    columns: Map[String, StructField]) extends RunnableCommand {
+    columnName: String,
+    newColumn: StructField) extends RunnableCommand {
 
   // TODO: support change column name/dataType/metadata/position.
   override def run(sparkSession: SparkSession): Seq[Row] = {
@@ -297,26 +298,24 @@ case class AlterTableChangeColumnsCommand(
     val resolver = sparkSession.sessionState.conf.resolver
     DDLUtils.verifyAlterTableType(catalog, table, isView = false)
 
-    // Create a map that converts the origin column to the new column with changed comment, throw
-    // an AnalysisException if the column reference is invalid or the column name/dataType is
-    // changed.
-    val columnsMap = columns.map { case (oldName: String, newField: StructField) =>
-      // Find the origin column from schema by column name.
-      val originColumn = findColumnByName(table.schema, oldName, resolver)
-      // Throw an AnalysisException if the column name/dataType is changed.
-      if (!columnEqual(originColumn, newField, resolver)) {
-        throw new AnalysisException(
-          "ALTER TABLE CHANGE COLUMN is not supported for changing column " +
-            s"'${originColumn.name}' with type '${originColumn.dataType}' to " +
-            s"'${newField.name}' with type '${newField.dataType}'")
-      }
-      // Create a new column from the origin column with the new comment.
-      val newColumn = addComment(originColumn, newField.getComment)
-      // Create the map from origin column to changed column
-      originColumn.name -> newColumn
+    // Find the origin column from schema by column name.
+    val originColumn = findColumnByName(table.schema, columnName, resolver)
+    // Throw an AnalysisException if the column name/dataType is changed.
+    if (!columnEqual(originColumn, newColumn, resolver)) {
+      throw new AnalysisException(
+        "ALTER TABLE CHANGE COLUMN is not supported for changing column " +
+          s"'${originColumn.name}' with type '${originColumn.dataType}' to " +
+          s"'${newColumn.name}' with type '${newColumn.dataType}'")
     }
 
-    val newSchema = table.schema.fields.map(field => columnsMap.getOrElse(field.name, field))
+    val newSchema = table.schema.fields.map { field =>
+      if (field.name == originColumn.name) {
+        // Create a new column from the origin column with the new comment.
+        addComment(field, newColumn.getComment)
+      } else {
+        field
+      }
+    }
     val newTable = table.copy(schema = StructType(newSchema))
     catalog.alterTable(newTable)
 

sql/core/src/test/resources/sql-tests/inputs/change-column.sql

@@ -4,22 +4,21 @@ DESC test_change;
 
 -- Change column name (not supported yet)
 ALTER TABLE test_change CHANGE a a1 INT;
-ALTER TABLE test_change CHANGE b b1 STRING, c c1 INT;
 DESC test_change;
 
 -- Change column dataType (not supported yet)
 ALTER TABLE test_change CHANGE a a STRING;
-ALTER TABLE test_change CHANGE b b INT, c c DOUBLE;
 DESC test_change;
 
 -- Change column position (not supported yet)
 ALTER TABLE test_change CHANGE a a INT AFTER b;
-ALTER TABLE test_change CHANGE b b STRING FIRST, c c INT AFTER b;
+ALTER TABLE test_change CHANGE b b STRING FIRST;
 DESC test_change;
 
 -- Change column comment
 ALTER TABLE test_change CHANGE a a INT COMMENT 'this is column a';
-ALTER TABLE test_change CHANGE b b STRING COMMENT '#*02?`', c c INT COMMENT '';
+ALTER TABLE test_change CHANGE b b STRING COMMENT '#*02?`';
+ALTER TABLE test_change CHANGE c c INT COMMENT '';
 DESC test_change;
 
 -- Don't change anything.