Improved PostgreSQL compatibility for ALTER TABLE ALTER COLUMN.

h2/src/main/org/h2/command/Parser.java

@@ -4451,18 +4451,32 @@ public class Parser {
                 String newName = readColumnIdentifier();
                 command.setNewColumnName(newName);
                 return command;
-            } else if (readIf("SET")) {
-                if (readIf("DATA")) {
-                    // Derby compatibility
-                    read("TYPE");
-                    Column newColumn = parseColumnForTable(columnName, column.isNullable());
+            } else if (readIf("DROP")) {
+                // PostgreSQL compatibility
+                if (readIf("DEFAULT")) {
                     AlterTableAlterColumn command = new AlterTableAlterColumn(session, table.getSchema());
                     command.setTable(table);
-                    command.setType(AlterTableAlterColumn.CHANGE_TYPE);
                     command.setOldColumn(column);
-                    command.setNewColumn(newColumn);
+                    command.setType(AlterTableAlterColumn.DEFAULT);
+                    command.setDefaultExpression(null);
                     return command;
                 }
+                read("NOT");
+                read("NULL");
+                AlterTableAlterColumn command = new AlterTableAlterColumn(session, table.getSchema());
+                command.setTable(table);
+                command.setOldColumn(column);
+                command.setType(AlterTableAlterColumn.NULL);
+                return command;
+            } else if (readIf("TYPE")) {
+                // PostgreSQL compatibility
+                return parseAlterTableAlterColumnType(table, columnName, column);
+            } else if (readIf("SET")) {
+                if (readIf("DATA")) {
+                    // Derby compatibility
+                    read("TYPE");
+                    return parseAlterTableAlterColumnType(table, columnName, column);
+                }
                 AlterTableAlterColumn command = new AlterTableAlterColumn(session, table.getSchema());
                 command.setTable(table);
                 command.setOldColumn(column);
@@ -4494,6 +4508,13 @@ public class Parser {
                 command.setSelectivity(readExpression());
                 return command;
             } else {
+                return parseAlterTableAlterColumnType(table, columnName, column);
+            }
+        }
+        throw getSyntaxError();
+    }
+
+    private AlterTableAlterColumn parseAlterTableAlterColumnType(Table table, String columnName, Column column) {
         Column newColumn = parseColumnForTable(columnName, column.isNullable());
         AlterTableAlterColumn command = new AlterTableAlterColumn(session, table.getSchema());
         command.setTable(table);
@@ -4502,9 +4523,6 @@ public class Parser {
         command.setNewColumn(newColumn);
         return command;
     }
-        }
-        throw getSyntaxError();
-    }
 
     private AlterTableAlterColumn parseAlterTableAddColumn(Table table) {
         readIf("COLUMN");

h2/src/test/org/h2/test/testSimple.in.txt

+create table test(id int);
+alter table test alter column id set default 'x';
+select column_default from information_schema.columns c where c.table_name = 'TEST' and c.column_name = 'ID';
+> 'x';
+alter table test alter column id set not null;
+select is_nullable from information_schema.columns c where c.table_name = 'TEST' and c.column_name = 'ID';
+> NO;
+alter table test alter column id set data type varchar;
+select type_name from information_schema.columns c where c.table_name = 'TEST' and c.column_name = 'ID';
+> VARCHAR;
+alter table test alter column id type int;
+select type_name from information_schema.columns c where c.table_name = 'TEST' and c.column_name = 'ID';
+> INTEGER;
+alter table test alter column id drop default;
+select column_default from information_schema.columns c where c.table_name = 'TEST' and c.column_name = 'ID';
+> null;
+alter table test alter column id drop not null;
+select is_nullable from information_schema.columns c where c.table_name = 'TEST' and c.column_name = 'ID';
+> YES;
+drop table test;
 select cast(cast(0.1 as real) as decimal);
 > 0.1;
 select cast(cast(95605327.73 as float) as decimal);