presto-hive/src/main/java/io/prestosql/plugin/hive/metastore/file/FileHiveMetastore.java/FileHiveMetastore/dropColumn
class FileHiveMetastore:    @Override
    public synchronized void dropColumn(HiveIdentity identity, String databaseName, String tableName, String columnName)
    {
        alterTable(databaseName, tableName, oldTable -> {
            verifyCanDropColumn(this, identity, databaseName, tableName, columnName);
            if (!oldTable.getColumn(columnName).isPresent()) {
                SchemaTableName name = new SchemaTableName(databaseName, tableName);
                throw new ColumnNotFoundException(name, columnName);
            }

            ImmutableList.Builder<Column> newDataColumns = ImmutableList.builder();
            for (Column fieldSchema : oldTable.getDataColumns()) {
                if (!fieldSchema.getName().equals(columnName)) {
                    newDataColumns.add(fieldSchema);
                }
            }

            return oldTable.withDataColumns(newDataColumns.build());
        });
    }