Contribution from Steve McLeod steve.mcleod@gmail.com

Modify ALTER TABLE ADD to support adding multiple columns in one command.

h2/src/docsrc/help/help.csv

@@ -211,8 +211,9 @@ ALTER SEQUENCE SEQ_ID RESTART WITH 1000
 "
 
 "Commands (DDL)","ALTER TABLE ADD","
-ALTER TABLE tableName ADD [ IF NOT EXISTS ] name dataType [ DEFAULT expression ]
-[ [ NOT ] NULL ] [ AUTO_INCREMENT | IDENTITY ] [ BEFORE columnName ]
+ALTER TABLE tableName ADD [ COLUMN ]
+{ [ IF NOT EXISTS ] columnDefinition [ BEFORE columnName ]
+    | ( { columnDefinition } [,...] ) }
 ","
 Adds a new column to a table.
 This command commits an open transaction.

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,8 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>Issue 380: ALTER TABLE ADD FOREIGN KEY with an explicit index didn't verify
+<ul><li>ALTER TABLE ADD can now add more than one column at a time.
+</li><li>Issue 380: ALTER TABLE ADD FOREIGN KEY with an explicit index didn't verify
     the index can be used, which would lead to a NullPointerException later on.
 </li><li>The wrong kind of exception (NullPointerException) was thrown in a UNION query
     with an incorrect ORDER BY expression.

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

@@ -4948,19 +4948,37 @@ public class Parser {
 
     private AlterTableAlterColumn parseAlterTableAddColumn(Table table) {
         readIf("COLUMN");
-        boolean ifNotExists = readIfNoExists();
         Schema schema = table.getSchema();
         AlterTableAlterColumn command = new AlterTableAlterColumn(session, schema);
-        command.setIfNotExists(ifNotExists);
         command.setType(CommandInterface.ALTER_TABLE_ADD_COLUMN);
         command.setTable(table);
-        String columnName = readColumnIdentifier();
-        Column column = parseColumnForTable(columnName, true);
-        command.setNewColumn(column);
-        if (readIf("BEFORE")) {
-            command.setAddBefore(readColumnIdentifier());
+        ArrayList<Column> columnsToAdd = New.arrayList();
+
+        boolean b = readIf("(");
+        if (b) {
+            command.setIfNotExists(false);
+            do{
+                String columnName = readColumnIdentifier();
+                Column column = parseColumnForTable(columnName, true);
+                columnsToAdd.add(column);
+            }   while (readIf(","));
+            read(")");
+            command.setNewColumns(columnsToAdd);
+
+        } else {
+            boolean ifNotExists = readIfNoExists();
+            command.setIfNotExists(ifNotExists);
+            String columnName = readColumnIdentifier();
+            Column column = parseColumnForTable(columnName, true);
+            columnsToAdd.add(column);
+            if (readIf("BEFORE")) {
+                command.setAddBefore(readColumnIdentifier());
+            }
+
         }
+        command.setNewColumns(columnsToAdd);
         return command;
+
     }
 
     private int parseAction() {

h2/src/main/org/h2/command/ddl/AlterTableAlterColumn.java

@@ -55,6 +55,7 @@ public class AlterTableAlterColumn extends SchemaCommand {
     private Expression newSelectivity;
     private String addBefore;
     private boolean ifNotExists;
+    private ArrayList<Column> columnsToAdd;
 
     public AlterTableAlterColumn(Session session, Schema schema) {
         super(session, schema);
@@ -82,81 +83,89 @@ public class AlterTableAlterColumn extends SchemaCommand {
         if (newColumn != null) {
             checkDefaultReferencesTable(newColumn.getDefaultExpression());
         }
-        switch (type) {
-        case CommandInterface.ALTER_TABLE_ALTER_COLUMN_NOT_NULL: {
-            if (!oldColumn.isNullable()) {
-                // no change
-                break;
+        if (columnsToAdd != null) {
+            for (Column column : columnsToAdd) {
+                checkDefaultReferencesTable(column.getDefaultExpression());
             }
-            checkNoNullValues();
-            oldColumn.setNullable(false);
-            db.update(session, table);
-            break;
         }
-        case CommandInterface.ALTER_TABLE_ALTER_COLUMN_NULL: {
-            if (oldColumn.isNullable()) {
-                // no change
+        switch (type) {
+            case CommandInterface.ALTER_TABLE_ALTER_COLUMN_NOT_NULL: {
+                if (!oldColumn.isNullable()) {
+                    // no change
+                    break;
+                }
+                checkNoNullValues();
+                oldColumn.setNullable(false);
+                db.update(session, table);
                 break;
             }
-            checkNullable();
-            oldColumn.setNullable(true);
-            db.update(session, table);
-            break;
-        }
-        case CommandInterface.ALTER_TABLE_ALTER_COLUMN_DEFAULT: {
-            checkDefaultReferencesTable(defaultExpression);
-            oldColumn.setSequence(null);
-            oldColumn.setDefaultExpression(session, defaultExpression);
-            removeSequence(sequence);
-            db.update(session, table);
-            break;
-        }
-        case CommandInterface.ALTER_TABLE_ALTER_COLUMN_CHANGE_TYPE: {
-            // if the change is only increasing the precision, then we don't
-            // need to copy the table because the length is only a constraint,
-            // and does not affect the storage structure.
-            if (oldColumn.isWideningConversion(newColumn)) {
-                convertAutoIncrementColumn(newColumn);
-                oldColumn.copy(newColumn);
+            case CommandInterface.ALTER_TABLE_ALTER_COLUMN_NULL: {
+                if (oldColumn.isNullable()) {
+                    // no change
+                    break;
+                }
+                checkNullable();
+                oldColumn.setNullable(true);
                 db.update(session, table);
-            } else {
+                break;
+            }
+            case CommandInterface.ALTER_TABLE_ALTER_COLUMN_DEFAULT: {
+                checkDefaultReferencesTable(defaultExpression);
                 oldColumn.setSequence(null);
-                oldColumn.setDefaultExpression(session, null);
-                oldColumn.setConvertNullToDefault(false);
-                if (oldColumn.isNullable() && !newColumn.isNullable()) {
-                    checkNoNullValues();
-                } else if (!oldColumn.isNullable() && newColumn.isNullable()) {
-                    checkNullable();
+                oldColumn.setDefaultExpression(session, defaultExpression);
+                removeSequence(sequence);
+                db.update(session, table);
+                break;
+            }
+            case CommandInterface.ALTER_TABLE_ALTER_COLUMN_CHANGE_TYPE: {
+                // if the change is only increasing the precision, then we don't
+                // need to copy the table because the length is only a constraint,
+                // and does not affect the storage structure.
+                if (oldColumn.isWideningConversion(newColumn)) {
+                    convertAutoIncrementColumn(newColumn);
+                    oldColumn.copy(newColumn);
+                    db.update(session, table);
+                } else {
+                    oldColumn.setSequence(null);
+                    oldColumn.setDefaultExpression(session, null);
+                    oldColumn.setConvertNullToDefault(false);
+                    if (oldColumn.isNullable() && !newColumn.isNullable()) {
+                        checkNoNullValues();
+                    } else if (!oldColumn.isNullable() && newColumn.isNullable()) {
+                        checkNullable();
+                    }
+                    convertAutoIncrementColumn(newColumn);
+                    copyData();
+                }
+                break;
+            }
+            case CommandInterface.ALTER_TABLE_ADD_COLUMN: {
+                // ifNotExists only supported for single column add
+                if (ifNotExists && columnsToAdd.size() == 1 && table.doesColumnExist(columnsToAdd.get(0).getName())) {
+                    break;
+                }
+                for (Column column : columnsToAdd) {
+                    convertAutoIncrementColumn(column);
                 }
-                convertAutoIncrementColumn(newColumn);
                 copyData();
+                break;
             }
-            break;
-        }
-        case CommandInterface.ALTER_TABLE_ADD_COLUMN: {
-            if (ifNotExists && table.doesColumnExist(newColumn.getName())) {
+            case CommandInterface.ALTER_TABLE_DROP_COLUMN: {
+                if (table.getColumns().length == 1) {
+                    throw DbException.get(ErrorCode.CANNOT_DROP_LAST_COLUMN, oldColumn.getSQL());
+                }
+                table.dropSingleColumnConstraintsAndIndexes(session, oldColumn);
+                copyData();
                 break;
             }
-            convertAutoIncrementColumn(newColumn);
-            copyData();
-            break;
-        }
-        case CommandInterface.ALTER_TABLE_DROP_COLUMN: {
-            if (table.getColumns().length == 1) {
-                throw DbException.get(ErrorCode.CANNOT_DROP_LAST_COLUMN, oldColumn.getSQL());
+            case CommandInterface.ALTER_TABLE_ALTER_COLUMN_SELECTIVITY: {
+                int value = newSelectivity.optimize(session).getValue(session).getInt();
+                oldColumn.setSelectivity(value);
+                db.update(session, table);
+                break;
             }
-            table.dropSingleColumnConstraintsAndIndexes(session, oldColumn);
-            copyData();
-            break;
-        }
-        case CommandInterface.ALTER_TABLE_ALTER_COLUMN_SELECTIVITY: {
-            int value = newSelectivity.optimize(session).getValue(session).getInt();
-            oldColumn.setSelectivity(value);
-            db.update(session, table);
-            break;
-        }
-        default:
-            DbException.throwInternalError("type=" + type);
+            default:
+                DbException.throwInternalError("type=" + type);
         }
         return 0;
     }
@@ -266,7 +275,9 @@ public class AlterTableAlterColumn extends SchemaCommand {
             } else {
                 position = table.getColumn(addBefore).getColumnId();
             }
-            newColumns.add(position, newColumn);
+            for (Column column : columnsToAdd) {
+                newColumns.add(position++, column);
+            }
         } else if (type == CommandInterface.ALTER_TABLE_ALTER_COLUMN_CHANGE_TYPE) {
             int position = oldColumn.getColumnId();
             newColumns.remove(position);
@@ -298,7 +309,7 @@ public class AlterTableAlterColumn extends SchemaCommand {
             if (columnList.length() > 0) {
                 columnList.append(", ");
             }
-            if (type == CommandInterface.ALTER_TABLE_ADD_COLUMN && nc == newColumn) {
+            if (type == CommandInterface.ALTER_TABLE_ADD_COLUMN && columnsToAdd.contains(nc)) {
                 Expression def = nc.getDefaultExpression();
                 columnList.append(def == null ? "NULL" : def.getSQL());
             } else {
@@ -470,4 +481,7 @@ public class AlterTableAlterColumn extends SchemaCommand {
         this.ifNotExists = ifNotExists;
     }
 
+    public void setNewColumns(ArrayList<Column> columnsToAdd) {
+        this.columnsToAdd = columnsToAdd;
+    }
 }

h2/src/test/org/h2/test/db/TestAlter.java

@@ -40,6 +40,7 @@ public class TestAlter extends TestBase {
         testAlterTableAlterColumn();
         testAlterTableDropIdentityColumn();
         testAlterTableAddColumnIfNotExists();
+        testAlterTableAddMultipleColumns();
         testAlterTableAlterColumn2();
         conn.close();
         deleteDb("alter");
@@ -136,6 +137,15 @@ public class TestAlter extends TestBase {
         stat.execute("drop table t");
     }
 
+    private void testAlterTableAddMultipleColumns() throws SQLException {
+        stat.execute("create table t(x varchar) as select 'x'");
+        stat.execute("alter table t add (y int, z varchar)");
+        stat.execute("drop table t");
+        stat.execute("create table t(x varchar) as select 'x'");
+        stat.execute("alter table t add (y int)");
+        stat.execute("drop table t");
+    }
+
     private void testAlterTableAlterColumn2() throws SQLException {
         // ensure that increasing a VARCHAR columns length takes effect because
         // we optimize this case