improved odps sql parser. support change column. issue #1455

src/main/java/com/alibaba/druid/sql/parser/SQLStatementParser.java

@@ -881,6 +881,22 @@ public class SQLStatementParser extends SQLParser {
                     } else {
                         throw new ParserException("TODO " + lexer.token() + " " + lexer.stringVal());
                     }
+                } else if (identifierEquals("CHANGE")) {
+                    lexer.nextToken();
+                    accept(Token.COLUMN);
+                    SQLName columnName = this.exprParser.name();
+                    accept(Token.COMMENT);
+                    SQLExpr comment = this.exprParser.primary();
+
+                    SQLColumnDefinition columnDefinition = new SQLColumnDefinition();
+                    columnDefinition.setName(columnName);
+                    columnDefinition.setComment(comment);
+
+                    SQLAlterTableAlterColumn changeColumn = new SQLAlterTableAlterColumn();
+
+                    changeColumn.setColumn(columnDefinition);
+
+                    stmt.addItem(changeColumn);
                 } else if (lexer.token() == Token.WITH) {
                     lexer.nextToken();
                     acceptIdentifier("NOCHECK");

src/main/java/com/alibaba/druid/sql/visitor/SQLASTOutputVisitor.java

@@ -1637,9 +1637,13 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter implements Paramet
         return false;
     }
 
+    protected boolean isOdps() {
+        return JdbcConstants.ODPS.equals(dbType);
+    }
+
     @Override
     public boolean visit(SQLAlterTableAddColumn x) {
-        boolean odps = JdbcConstants.ODPS.equals(dbType);
+        boolean odps = isOdps();
         if (odps) {
             print0(ucase ? "ADD COLUMNS (" : "add columns (");
         } else {
@@ -1962,7 +1966,12 @@ public class SQLASTOutputVisitor extends SQLASTVisitorAdapter implements Paramet
 
     @Override
     public boolean visit(SQLAlterTableAlterColumn x) {
-        print0(ucase ? "ALTER COLUMN " : "alter column ");
+        boolean odps = isOdps();
+        if (odps) {
+            print0(ucase ? "CHANGE COLUMN " : "change column ");
+        } else {
+            print0(ucase ? "ALTER COLUMN " : "alter column ");
+        }
         x.getColumn().accept(this);
 
         if (x.isSetNotNull()) { // postgresql

src/test/java/com/alibaba/druid/bvt/sql/odps/OdpsAlterTableAddColumnsTest.java

@@ -24,7 +24,7 @@ import org.junit.Assert;
 
 import java.util.List;
 
-public class OdpsSelectTest19 extends TestCase {
+public class OdpsAlterTableAddColumnsTest extends TestCase {
 
     public void test_select() throws Exception {
         String sql = "alter table adl_smeta_column_indi_rule_relation_sdt add columns (rule_level string);";//