@Override
public ValidationErrors validate(DropColumnStatement dropColumnStatement, Database database, SqlGeneratorChain sqlGeneratorChain) {
    if (dropColumnStatement.isMultiple()) {
        ValidationErrors validationErrors = new ValidationErrors();
        DropColumnStatement firstColumn = dropColumnStatement.getColumns().get(0);

        for (DropColumnStatement drop : dropColumnStatement.getColumns()) {
            validationErrors.addAll(validateSingleColumn(drop));
            if (drop.getTableName() != null && !drop.getTableName().equals(firstColumn.getTableName())) {
                validationErrors.addError("All columns must be targeted at the same table");
            }
            if (drop.isMultiple()) {
                validationErrors.addError("Nested multiple drop column statements are not supported");
            }
        }
        return validationErrors;
    } else {
        return validateSingleColumn(dropColumnStatement);
    }
}
 

@Test
public void testRollbackSQL() throws RollbackImpossibleException {
    enableLogging();

    SqlStatement[] statements = generateRollbackStatements();
    Assertions.assertEquals(3, statements.length);
    Assertions.assertEquals(CommentStatement.class, statements[0].getClass());
    Assertions.assertEquals("pt-online-schema-change "
            + "--alter-foreign-keys-method=auto "
            + "--nocheck-unique-key-change "
            + "--alter=\"DROP COLUMN new_column\" "
            + "--host=localhost --port=3306 --user=user --password=*** --execute D=testdb,t=person",
            ((CommentStatement)statements[0]).getText());
    Assertions.assertEquals(CommentStatement.class, statements[1].getClass());
    Assertions.assertEquals(DropColumnStatement.class, statements[2].getClass());
}
 

@Test
public void testUpdateSQL() {
    enableLogging();

    SqlStatement[] statements = generateStatements();
    Assertions.assertEquals(3, statements.length);
    Assertions.assertEquals(CommentStatement.class, statements[0].getClass());
    Assertions.assertEquals("pt-online-schema-change "
            + "--alter-foreign-keys-method=auto "
            + "--nocheck-unique-key-change "
            + "--alter=\"DROP COLUMN col_test\" "
            + "--host=localhost --port=3306 --user=user --password=*** --execute D=testdb,t=person",
            ((CommentStatement)statements[0]).getText());
    Assertions.assertEquals(CommentStatement.class, statements[1].getClass());
    Assertions.assertEquals(DropColumnStatement.class, statements[2].getClass());
}
 

@Override
public Sql[] generateSql(final DropColumnStatement statement, final Database database,
      final SqlGeneratorChain sqlGeneratorChain) {

   String schemaName = statement.getSchemaName();
   if (schemaName == null) {
      schemaName = database.getDefaultSchemaName();
   }
   final String tableName = statement.getTableName();
   final String columnName = statement.getColumnName();
   final boolean isGeometryColumn = GeometryColumnsUtils.isGeometryColumn(database, schemaName,
         tableName, columnName);
   final List<Sql> list = new ArrayList<Sql>();
   if (isGeometryColumn) {
      dropSpatialIndexIfExists(statement.getCatalogName(), schemaName, tableName, database, list);
      final String sql = "CALL DropGeometryColumn('" + schemaName + "', '" + tableName + "', '"
            + columnName + "')";
      final Column column = getAffectedColumn(statement);
      final Sql dropGeometryColumn = new UnparsedSql(sql, column);
      list.add(dropGeometryColumn);
   } else {
      list.addAll(Arrays.asList(sqlGeneratorChain.generateSql(statement, database)));
   }
   return list.toArray(new Sql[list.size()]);
}
 

@Test(dataProvider = "generateSqlTestData")
public void testGenerateSql(final DropColumnStatement statement, final Database database,
      final Sql[] expected) throws DatabaseException {
   final DropGeometryColumnGeneratorGeoDB generator = new DropGeometryColumnGeneratorGeoDB();
   final SqlGeneratorChain sqlGeneratorChain = mock(SqlGeneratorChain.class);
   when(sqlGeneratorChain.generateSql(statement, database)).thenReturn(new Sql[0]);
   final Sql[] result = generator.generateSql(statement, database, sqlGeneratorChain);
   assertEquals(result.length, expected.length);
   if (result.length > 0) {
      for (int ii = 0; ii < result.length; ii++) {
         final Sql resultSql = result[ii];
         final Sql expectedSql = expected[ii];
         assertEquals(resultSql.toSql(), expectedSql.toSql());
      }
   }
}
 

private Sql[] generateMultipleColumnSql(DropColumnStatement dropColumnStatement, Database database, Map<String, String> columnsPreserved) {
    if (columnsPreserved == null) {
        throw new UnexpectedLiquibaseException("no columns to preserve");
    }
    List<Sql> result = new ArrayList<Sql>();
    Map<String, String> columnsPreservedCopy = new HashMap<String, String>(columnsPreserved);
    String alterTable;
    List<DropColumnStatement> columns = null;

    if (dropColumnStatement.isMultiple()) {
        columns = dropColumnStatement.getColumns();
        for (DropColumnStatement statement : columns) {
            columnsPreservedCopy.remove(statement.getColumnName());
        }
        alterTable = "ALTER TABLE " + database.escapeTableName(columns.get(0).getCatalogName(), columns.get(0).getSchemaName(), columns.get(0).getTableName()) + " REPLACE COLUMNS (";
    } else {
        columnsPreservedCopy.remove(dropColumnStatement.getColumnName());
        alterTable = "ALTER TABLE " + database.escapeTableName(dropColumnStatement.getCatalogName(), dropColumnStatement.getSchemaName(), dropColumnStatement.getTableName()) + " REPLACE COLUMNS (";
    }

    int i = 0;
    for (String columnName : columnsPreservedCopy.keySet()) {
        alterTable += database.escapeObjectName(columnName, Column.class) + " " + columnsPreservedCopy.get(columnName);
        if (i < columnsPreservedCopy.size() - 1) {
            alterTable += ",";
        } else {
            alterTable += ")";
        }
        i++;
    }

    if (dropColumnStatement.isMultiple()) {
        result.add(new UnparsedSql(alterTable, getAffectedColumns(columns)));
    } else {
        result.add(new UnparsedSql(alterTable, getAffectedColumn(dropColumnStatement)));
    }
    return result.toArray(new Sql[result.size()]);
}
 

private Column[] getAffectedColumns(List<DropColumnStatement> columns) {
    List<Column> affected = new ArrayList<Column>();
    for (DropColumnStatement column : columns) {
        affected.add(getAffectedColumn(column));
    }
    return affected.toArray(new Column[affected.size()]);
}
 

@Test
public void testWithoutPerconaRollback() throws RollbackImpossibleException {
    PTOnlineSchemaChangeStatement.available = false;
    SqlStatement[] statements = generateRollbackStatements();
    Assertions.assertEquals(1, statements.length);
    Assertions.assertEquals(DropColumnStatement.class, statements[0].getClass());
}
 

@Test
public void testWithoutPercona() {
    PTOnlineSchemaChangeStatement.available = false;
    SqlStatement[] statements = generateStatements();
    Assertions.assertEquals(1, statements.length);
    Assertions.assertEquals(DropColumnStatement.class, statements[0].getClass());
}
 

/**
 * Provides test data to {@link #testSupports(DropColumnStatement, Database, boolean)}.
 * 
 * @return the test data.
 */
@DataProvider
public Object[][] supportsTestData() {
   final DropColumnStatement statement = new DropColumnStatement(null, null, null, null);
   return new Object[][] { new Object[] { statement, new DerbyDatabase(), true },
         new Object[] { statement, new H2Database(), true },
         new Object[] { statement, new OracleDatabase(), false }, };
}
 

@Override
public boolean supports(DropColumnStatement dropColumnStatement, Database database) {
    return database instanceof HiveDatabase && super.supports(dropColumnStatement, database);
}
 

private ValidationErrors validateSingleColumn(DropColumnStatement dropColumnStatement) {
    ValidationErrors validationErrors = new ValidationErrors();
    validationErrors.checkRequiredField("tableName", dropColumnStatement.getTableName());
    validationErrors.checkRequiredField("columnName", dropColumnStatement.getColumnName());
    return validationErrors;
}
 

@Override
public Sql[] generateSql(DropColumnStatement dropColumnStatement, Database database, SqlGeneratorChain sqlGeneratorChain) {
    Map<String, String> columnsPreserved = null;
    columnsPreserved = columnsMap((HiveDatabase) database, dropColumnStatement);
    return generateMultipleColumnSql(dropColumnStatement, database, columnsPreserved);
}
 

private Column getAffectedColumn(DropColumnStatement statement) {
    return new Column().setName(statement.getColumnName()).setRelation(new Table().setName(statement.getTableName()).setSchema(statement.getCatalogName(), statement.getSchemaName()));
}
 

/**
 * @see liquibase.sqlgenerator.core.AbstractSqlGenerator#supports(liquibase.statement.SqlStatement,
 *      liquibase.database.Database)
 */
@Override
public boolean supports(final DropColumnStatement statement, final Database database) {
   return database instanceof DerbyDatabase || database instanceof H2Database;
}
 

@Override
public ValidationErrors validate(final DropColumnStatement statement, final Database database,
      final SqlGeneratorChain sqlGeneratorChain) {
   return sqlGeneratorChain.validate(statement, database);
}
 

/**
 * Tests {@link DropGeometryColumnGeneratorGeoDB#supports(DropColumnStatement, Database)}.
 * 
 * @param statement
 *           the add column statement.
 * @param database
 *           the database instance.
 * @param expected
 *           the expected result from <code>supports</code>.
 */
@Test(dataProvider = "supportsTestData")
public void testSupports(final DropColumnStatement statement, final Database database,
      final boolean expected) {
   final DropGeometryColumnGeneratorGeoDB generator = new DropGeometryColumnGeneratorGeoDB();
   final boolean result = generator.supports(statement, database);
   assertEquals(result, expected);
}