[SPARK-17910][SQL] Allow users to update the comment of a column

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

@@ -89,6 +89,8 @@ statement
         SET TBLPROPERTIES tablePropertyList                            #setTableProperties
     | ALTER (TABLE | VIEW) tableIdentifier
         UNSET TBLPROPERTIES (IF EXISTS)? tablePropertyList             #unsetTableProperties
+    | ALTER TABLE tableIdentifier partitionSpec?
+        CHANGE COLUMN? identifier colType colPosition?                 #changeColumn
     | ALTER TABLE tableIdentifier (partitionSpec)?
         SET SERDE STRING (WITH SERDEPROPERTIES tablePropertyList)?     #setTableSerDe
     | ALTER TABLE tableIdentifier (partitionSpec)?
@@ -192,7 +194,6 @@ unsupportedHiveNativeCommands
     | kw1=ALTER kw2=TABLE tableIdentifier partitionSpec? kw3=CONCATENATE
     | kw1=ALTER kw2=TABLE tableIdentifier partitionSpec? kw3=SET kw4=FILEFORMAT
     | kw1=ALTER kw2=TABLE tableIdentifier partitionSpec? kw3=ADD kw4=COLUMNS
-    | kw1=ALTER kw2=TABLE tableIdentifier partitionSpec? kw3=CHANGE kw4=COLUMN?
     | kw1=ALTER kw2=TABLE tableIdentifier partitionSpec? kw3=REPLACE kw4=COLUMNS
     | kw1=START kw2=TRANSACTION
     | kw1=COMMIT
@@ -578,6 +579,10 @@ intervalValue
     | STRING
     ;
 
+colPosition
+    : FIRST | AFTER identifier
+    ;
+
 dataType
     : complex=ARRAY '<' dataType '>'                            #complexDataType
     | complex=MAP '<' dataType ',' dataType '>'                 #complexDataType
@@ -669,7 +674,7 @@ number
 nonReserved
     : SHOW | TABLES | COLUMNS | COLUMN | PARTITIONS | FUNCTIONS | DATABASES
     | ADD
-    | OVER | PARTITION | RANGE | ROWS | PRECEDING | FOLLOWING | CURRENT | ROW | LAST | FIRST
+    | OVER | PARTITION | RANGE | ROWS | PRECEDING | FOLLOWING | CURRENT | ROW | LAST | FIRST | AFTER
     | MAP | ARRAY | STRUCT
     | LATERAL | WINDOW | REDUCE | TRANSFORM | USING | SERDE | SERDEPROPERTIES | RECORDREADER
     | DELIMITED | FIELDS | TERMINATED | COLLECTION | ITEMS | KEYS | ESCAPED | LINES | SEPARATED
@@ -759,6 +764,7 @@ PRECEDING: 'PRECEDING';
 FOLLOWING: 'FOLLOWING';
 CURRENT: 'CURRENT';
 FIRST: 'FIRST';
+AFTER: 'AFTER';
 LAST: 'LAST';
 ROW: 'ROW';
 WITH: 'WITH';

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

@@ -31,7 +31,7 @@ import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, OneRowRelation,
 import org.apache.spark.sql.execution.command._
 import org.apache.spark.sql.execution.datasources.{CreateTable, _}
 import org.apache.spark.sql.internal.{HiveSerDe, SQLConf, VariableSubstitution}
-import org.apache.spark.sql.types.StructType
+import org.apache.spark.sql.types.{StructField, StructType}
 
 /**
  * Concrete parser for Spark SQL statements.
@@ -876,6 +876,33 @@ class SparkSqlAstBuilder(conf: SQLConf) extends AstBuilder {
       visitLocationSpec(ctx.locationSpec))
   }
 
+  /**
+   * Create a [[AlterTableChangeColumnCommand]] command.
+   *
+   * For example:
+   * {{{
+   *   ALTER TABLE table [PARTITION partition_spec]
+   *   CHANGE [COLUMN] column_old_name column_new_name column_dataType [COMMENT column_comment]
+   *   [FIRST | AFTER column_name];
+   * }}}
+   */
+  override def visitChangeColumn(ctx: ChangeColumnContext): LogicalPlan = withOrigin(ctx) {
+    if (ctx.partitionSpec != null) {
+      operationNotAllowed("ALTER TABLE table PARTITION partition_spec CHANGE COLUMN", ctx)
+    }
+
+    if (ctx.colPosition != null) {
+      operationNotAllowed(
+        "ALTER TABLE table [PARTITION partition_spec] CHANGE COLUMN ... FIRST | AFTER otherCol",
+        ctx)
+    }
+
+    AlterTableChangeColumnCommand(
+      tableName = visitTableIdentifier(ctx.tableIdentifier),
+      columnName = ctx.identifier.getText,
+      newColumn = visitColType(ctx.colType))
+  }
+
   /**
    * Create location string.
    */

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

@@ -274,6 +274,77 @@ case class AlterTableUnsetPropertiesCommand(
 
 }
 
+
+/**
+ * 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:
+ * {{{
+ *   ALTER TABLE table_identifier
+ *   CHANGE [COLUMN] column_old_name column_new_name column_dataType [COMMENT column_comment]
+ *   [FIRST | AFTER column_name];
+ * }}}
+ */
+case class AlterTableChangeColumnCommand(
+    tableName: TableIdentifier,
+    columnName: String,
+    newColumn: StructField) extends RunnableCommand {
+
+  // TODO: support change column name/dataType/metadata/position.
+  override def run(sparkSession: SparkSession): Seq[Row] = {
+    val catalog = sparkSession.sessionState.catalog
+    val table = catalog.getTableMetadata(tableName)
+    val resolver = sparkSession.sessionState.conf.resolver
+    DDLUtils.verifyAlterTableType(catalog, table, isView = false)
+
+    // 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 =>
+      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)
+
+    Seq.empty[Row]
+  }
+
+  // Find the origin column from schema by column name, throw an AnalysisException if the column
+  // reference is invalid.
+  private def findColumnByName(
+      schema: StructType, name: String, resolver: Resolver): StructField = {
+    schema.fields.collectFirst {
+      case field if resolver(field.name, name) => field
+    }.getOrElse(throw new AnalysisException(
+      s"Invalid column reference '$name', table schema is '${schema}'"))
+  }
+
+  // Add the comment to a column, if comment is empty, return the original column.
+  private def addComment(column: StructField, comment: Option[String]): StructField = {
+    comment.map(column.withComment(_)).getOrElse(column)
+  }
+
+  // Compare a [[StructField]] to another, return true if they have the same column
+  // name(by resolver) and dataType.
+  private def columnEqual(
+      field: StructField, other: StructField, resolver: Resolver): Boolean = {
+    resolver(field.name, other.name) && field.dataType == other.dataType
+  }
+}
+
 /**
  * A command that sets the serde class and/or serde properties of a table/view.
  *

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

@@ -0,0 +1,55 @@
+-- Create the origin table
+CREATE TABLE test_change(a INT, b STRING, c INT);
+DESC test_change;
+
+-- Change column name (not supported yet)
+ALTER TABLE test_change CHANGE a a1 INT;
+DESC test_change;
+
+-- Change column dataType (not supported yet)
+ALTER TABLE test_change CHANGE a a STRING;
+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;
+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?`';
+ALTER TABLE test_change CHANGE c c INT COMMENT '';
+DESC test_change;
+
+-- Don't change anything.
+ALTER TABLE test_change CHANGE a a INT COMMENT 'this is column a';
+DESC test_change;
+
+-- Change a invalid column
+ALTER TABLE test_change CHANGE invalid_col invalid_col INT;
+DESC test_change;
+
+-- Change column name/dataType/position/comment together (not supported yet)
+ALTER TABLE test_change CHANGE a a1 STRING COMMENT 'this is column a1' AFTER b;
+DESC test_change;
+
+-- Check the behavior with different values of CASE_SENSITIVE
+SET spark.sql.caseSensitive=false;
+ALTER TABLE test_change CHANGE a A INT COMMENT 'this is column A';
+SET spark.sql.caseSensitive=true;
+ALTER TABLE test_change CHANGE a A INT COMMENT 'this is column A1';
+DESC test_change;
+
+-- Change column can't apply to a temporary/global_temporary view
+CREATE TEMPORARY VIEW temp_view(a, b) AS SELECT 1, "one";
+ALTER TABLE temp_view CHANGE a a INT COMMENT 'this is column a';
+CREATE GLOBAL TEMPORARY VIEW global_temp_view(a, b) AS SELECT 1, "one";
+ALTER TABLE global_temp.global_temp_view CHANGE a a INT COMMENT 'this is column a';
+
+-- Change column in partition spec (not supported yet)
+CREATE TABLE partition_table(a INT, b STRING) PARTITIONED BY (c INT, d STRING);
+ALTER TABLE partition_table PARTITION (c = 1) CHANGE COLUMN a new_a INT;
+
+-- DROP TEST TABLE
+DROP TABLE test_change;
+DROP TABLE partition_table;