Add support for dropping multiple columns in ALTER TABLE DROP COLUMN...

h2/src/docsrc/help/help.csv

@@ -289,12 +289,13 @@ ALTER TABLE TEST ALTER COLUMN NAME SET NULL;
 "
 
 "Commands (DDL)","ALTER TABLE DROP COLUMN","
-ALTER TABLE tableName DROP COLUMN [ IF EXISTS ] columnName
+ALTER TABLE tableName DROP COLUMN [ IF EXISTS ] ( columnName [,...] )
 ","
-Removes a column from a table.
+Removes column(s) from a table.
 This command commits an open transaction in this connection.
 ","
 ALTER TABLE TEST DROP COLUMN NAME
+ALTER TABLE TEST DROP COLUMN NAME1, NAME2
 "
 
 "Commands (DDL)","ALTER TABLE DROP CONSTRAINT","

h2/src/docsrc/html/changelog.html

@@ -27,6 +27,8 @@ Change Log
 
 <h2>Version 1.4.189 Beta (2015-09-13)</h2>
 <ul>
+<li>Add support for dropping multiple columns in ALTER TABLE DROP COLUMN...
+</li>
 <li>Fix bug in XA management when doing rollback after prepare. Patch by Stephane Lacoin.
 </li>
 <li>MVStore CLOB and BLOB: An exception with the message "Block not found" could be thrown

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

@@ -5415,12 +5415,17 @@ public class Parser {
                 AlterTableAlterColumn command = new AlterTableAlterColumn(
                         session, table.getSchema());
                 command.setType(CommandInterface.ALTER_TABLE_DROP_COLUMN);
-                String columnName = readColumnIdentifier();
+                ArrayList<Column> columnsToRemove = New.arrayList();
+                do {
+                    String columnName = readColumnIdentifier();
+                    if (ifExists && !table.doesColumnExist(columnName)) {
+                        return new NoOperation(session);
+                    }
+                    Column column = table.getColumn(columnName);
+                    columnsToRemove.add(column);
+                } while (readIf(","));
                 command.setTable(table);
-                if (ifExists && !table.doesColumnExist(columnName)) {
-                    return new NoOperation(session);
-                }
-                command.setOldColumn(table.getColumn(columnName));
+                command.setColumnsToRemove(columnsToRemove);
                 return command;
             }
         } else if (readIf("CHANGE")) {

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

@@ -7,7 +7,7 @@ package org.h2.command.ddl;
 
 import java.util.ArrayList;
 import java.util.HashSet;
-
+import java.util.Iterator;
 import org.h2.api.ErrorCode;
 import org.h2.command.CommandInterface;
 import org.h2.command.Parser;
@@ -57,6 +57,7 @@ public class AlterTableAlterColumn extends SchemaCommand {
     private String addAfter;
     private boolean ifNotExists;
     private ArrayList<Column> columnsToAdd;
+    private ArrayList<Column> columnsToRemove;
 
     public AlterTableAlterColumn(Session session, Schema schema) {
         super(session, schema);
@@ -85,7 +86,6 @@ public class AlterTableAlterColumn extends SchemaCommand {
         session.getUser().checkRight(table, Right.ALL);
         table.checkSupportAlter();
         table.lock(session, true, true);
-        Sequence sequence = oldColumn == null ? null : oldColumn.getSequence();
         if (newColumn != null) {
             checkDefaultReferencesTable(newColumn.getDefaultExpression());
         }
@@ -116,6 +116,7 @@ public class AlterTableAlterColumn extends SchemaCommand {
             break;
         }
         case CommandInterface.ALTER_TABLE_ALTER_COLUMN_DEFAULT: {
+            Sequence sequence = oldColumn == null ? null : oldColumn.getSequence();
             checkDefaultReferencesTable(defaultExpression);
             oldColumn.setSequence(null);
             oldColumn.setDefaultExpression(session, defaultExpression);
@@ -162,11 +163,11 @@ public class AlterTableAlterColumn extends SchemaCommand {
             break;
         }
         case CommandInterface.ALTER_TABLE_DROP_COLUMN: {
-            if (table.getColumns().length == 1) {
+            if (table.getColumns().length - columnsToRemove.size() < 1) {
                 throw DbException.get(ErrorCode.CANNOT_DROP_LAST_COLUMN,
-                        oldColumn.getSQL());
+                        columnsToRemove.get(0).getSQL());
             }
-            table.dropSingleColumnConstraintsAndIndexes(session, oldColumn);
+            table.dropMultipleColumnsConstraintsAndIndexes(session, columnsToRemove);
             copyData();
             break;
         }
@@ -282,8 +283,20 @@ public class AlterTableAlterColumn extends SchemaCommand {
             newColumns.add(col.getClone());
         }
         if (type == CommandInterface.ALTER_TABLE_DROP_COLUMN) {
-            int position = oldColumn.getColumnId();
-            newColumns.remove(position);
+            for (Column removeCol : columnsToRemove) {
+                Column foundCol = null;
+                for (Iterator<Column> iter = newColumns.iterator(); iter.hasNext(); ) {
+                    Column newCol = iter.next();
+                    if (newCol.getName() == removeCol.getName()) {
+                        foundCol = newCol;
+                        break;
+                    }
+                }
+                if (foundCol == null) {
+                    throw DbException.throwInternalError(removeCol.getCreateSQL());
+                }
+                newColumns.remove(foundCol);
+            }
         } else if (type == CommandInterface.ALTER_TABLE_ADD_COLUMN) {
             int position;
             if (addBefore != null) {
@@ -509,4 +522,8 @@ public class AlterTableAlterColumn extends SchemaCommand {
     public void setNewColumns(ArrayList<Column> columnsToAdd) {
         this.columnsToAdd = columnsToAdd;
     }
+
+    public void setColumnsToRemove(ArrayList<Column> columnsToRemove) {
+        this.columnsToRemove = columnsToRemove;
+    }
 }

h2/src/main/org/h2/table/Table.java

@@ -9,7 +9,6 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Set;
-
 import org.h2.api.ErrorCode;
 import org.h2.command.Prepared;
 import org.h2.constraint.Constraint;
@@ -531,49 +530,53 @@ public abstract class Table extends SchemaObjectBase {
     }
 
     /**
-     * Check that this column is not referenced by a multi-column constraint or
+     * Check that these columns are not referenced by a multi-column constraint or
      * multi-column index. If it is, an exception is thrown. Single-column
      * references and indexes are dropped.
      *
      * @param session the session
-     * @param col the column
+     * @param columsToDrop the columns to drop
      * @throws DbException if the column is referenced by multi-column
      *             constraints or indexes
      */
-    public void dropSingleColumnConstraintsAndIndexes(Session session,
-            Column col) {
-        ArrayList<Constraint> constraintsToDrop = New.arrayList();
+    public void dropMultipleColumnsConstraintsAndIndexes(Session session,
+            ArrayList<Column> columsToDrop) {
+        HashSet<Constraint> constraintsToDrop = New.hashSet();
         if (constraints != null) {
-            for (int i = 0, size = constraints.size(); i < size; i++) {
-                Constraint constraint = constraints.get(i);
-                HashSet<Column> columns = constraint.getReferencedColumns(this);
-                if (!columns.contains(col)) {
-                    continue;
-                }
-                if (columns.size() == 1) {
-                    constraintsToDrop.add(constraint);
-                } else {
-                    throw DbException.get(
-                            ErrorCode.COLUMN_IS_REFERENCED_1, constraint.getSQL());
+            for (Column col : columsToDrop) {
+                for (int i = 0, size = constraints.size(); i < size; i++) {
+                    Constraint constraint = constraints.get(i);
+                    HashSet<Column> columns = constraint.getReferencedColumns(this);
+                    if (!columns.contains(col)) {
+                        continue;
+                    }
+                    if (columns.size() == 1) {
+                        constraintsToDrop.add(constraint);
+                    } else {
+                        throw DbException.get(
+                                ErrorCode.COLUMN_IS_REFERENCED_1, constraint.getSQL());
+                    }
                 }
             }
         }
-        ArrayList<Index> indexesToDrop = New.arrayList();
+        HashSet<Index> indexesToDrop = New.hashSet();
         ArrayList<Index> indexes = getIndexes();
         if (indexes != null) {
-            for (int i = 0, size = indexes.size(); i < size; i++) {
-                Index index = indexes.get(i);
-                if (index.getCreateSQL() == null) {
-                    continue;
-                }
-                if (index.getColumnIndex(col) < 0) {
-                    continue;
-                }
-                if (index.getColumns().length == 1) {
-                    indexesToDrop.add(index);
-                } else {
-                    throw DbException.get(
-                            ErrorCode.COLUMN_IS_REFERENCED_1, index.getSQL());
+            for (Column col : columsToDrop) {
+                for (int i = 0, size = indexes.size(); i < size; i++) {
+                    Index index = indexes.get(i);
+                    if (index.getCreateSQL() == null) {
+                        continue;
+                    }
+                    if (index.getColumnIndex(col) < 0) {
+                        continue;
+                    }
+                    if (index.getColumns().length == 1) {
+                        indexesToDrop.add(index);
+                    } else {
+                        throw DbException.get(
+                                ErrorCode.COLUMN_IS_REFERENCED_1, index.getSQL());
+                    }
                 }
             }
         }

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

@@ -10,7 +10,6 @@ import java.sql.DatabaseMetaData;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
-
 import org.h2.api.ErrorCode;
 import org.h2.test.TestBase;
 
@@ -38,6 +37,7 @@ public class TestAlter extends TestBase {
         stat = conn.createStatement();
         testAlterTableAlterColumnAsSelfColumn();
         testAlterTableDropColumnWithReferences();
+        testAlterTableDropMultipleColumns();
         testAlterTableAlterColumnWithConstraint();
         testAlterTableAlterColumn();
         testAlterTableAddColumnIdentity();
@@ -108,6 +108,17 @@ public class TestAlter extends TestBase {
 
     }
 
+    private void testAlterTableDropMultipleColumns() throws SQLException {
+        stat.execute("create table test(id int, name varchar, name2 varchar)");
+        stat.execute("alter table test drop column name, name2");
+        stat.execute("drop table test");
+
+        stat.execute("create table test(id int, name varchar, name2 varchar)");
+        assertThrows(ErrorCode.CANNOT_DROP_LAST_COLUMN, stat).
+            execute("alter table test drop column id, name, name2");
+        stat.execute("drop table test");
+    }
+
     /**
      * Tests a bug we used to have where altering the name of a column that had
      * a check constraint that referenced itself would result in not being able