O componente Zend_Search_Lucene trabalha com os formatos de índice Java Lucene 1.4-1.9, 2.1 e 2.3.

O formato de índice corrente pode ser solicitado através da chamada $index->getFormatVersion(). Ela retorna um dos seguintes valores:

As modificações no índice são realizadas apenas se qualquer atualização do índice for feita. Isso acontece se um novo documento for adicionado a um índice ou uma otimização de índice for iniciada manualmente através da chamada $index->optimize().

Nesse caso, Zend_Search_Lucene pode converter o índice para a versão superior. Isso sempre acontece para os índices no formato Zend_Search_Lucene::FORMAT_PRE_2_1, que são automaticamente convertidos para o formato 2.1.

Você pode gerenciar o processo de conversão e atribuir o formato de índice de destino com $index->setFormatVersion() que toma como parâmetro a constante Zend_Search_Lucene::FORMAT_2_1 ou Zend_Search_Lucene::FORMAT_2_3:

Conversões para versões anteriores de formatos não são suportadas.

The Zend_Search_Lucene object uses the destructor method to commit changes and clean up resources.

It stores added documents in memory and dumps new index segment to disk depending on MaxBufferedDocs parameter.

If MaxBufferedDocs limit is not reached then there are some "unsaved" documents which are saved as a new segment in the object's destructor method. The index auto-optimization procedure is invoked if necessary depending on the values of the MaxBufferedDocs, MaxMergeDocs and MergeFactor parameters.

Static object properties (see below) are destroyed after the last line of the executed script.

class Searcher {
    private static $_index;

    public static function initIndex() {
        self::$_index = Zend_Search_Lucene::open('path/to/index');
    }
}

Searcher::initIndex();

All the same, the destructor for static properties is correctly invoked at this point in the program's execution.

One potential problem is exception handling. Exceptions thrown by destructors of static objects don't have context, because the destructor is executed after the script has already completed.

You might see a "Fatal error: Exception thrown without a stack frame in Unknown on line 0" error message instead of exception description in such cases.

Zend_Search_Lucene provides a workaround to this problem with the commit() method. It saves all unsaved changes and frees memory used for storing new segments. You are free to use the commit operation any time- or even several times- during script execution. You can still use the Zend_Search_Lucene object for searching, adding or deleting document after the commit operation. But the commit() call guarantees that if there are no document added or deleted after the call to commit(), then the Zend_Search_Lucene destructor has nothing to do and will not throw exception:

class Searcher {
    private static $_index;

    public static function initIndex() {
        self::$_index = Zend_Search_Lucene::open('path/to/index');
    }

    ...

    public static function commit() {
        self::$_index->commit();
    }
}

Searcher::initIndex();

...

// Rotina de desligamento do script
...
Searcher::commit();
...