Changes

This [[Module Library|XQuery Module]] contains functions for handling ''streamablelazy'' items.

In contrast to standard XQuery items, a streamable lazy item contains only a reference to the actual data. The , and the data itself will only be retrieved if it is requested by an expression, or if the item is to be serialized. Hence, a streamable item only uses a few bytespossible errors will be postponed, and no additional memory is will be occupied during serializationby a lazy item as long as its contents has not been reqested yet.

The following BaseX functions return streamable lazy items:

* Streamable Lazy Base64 binaries:

* Streamable Lazy strings:

Some functions are capable of consuming the contents of lazy items in a ''streamable'' fashion: data will never not be cached, but instead passed on to another target (file, the calling expression, etc.). The following streaming functions are currently available:

* [[Archive Module]] (most functions)* Conversion Module: <code>[[Conversion Module#convert:binary-to-bytes|convert:binary-to-bytes]]</code>, <code>[[Conversion Module#convert:binary-to-string|convert:binary-to-string]]</code>* Database Module: <code>[[Database Module#db:store|db:store]]</code>* File Module: <code>[[File Module#file:write-binary|file:write-binary]]</code>* , <code>[[Fetch File Module#file:write-text|file:write-text]]</code>(if no encoding is specified)* [[Hashing Module]] (all functions)

All functions and errors in this module are assigned to the <code><nowiki>http://basex.org/modules/streamlazy</nowiki></code> namespace, which is statically bound to the {{Code|streamlazy}} prefix.<br/>All errors are assigned to the <code><nowiki>http://basex.org/errors</nowiki></code> namespace, which is statically bound to the {{Code|bxerr}} prefix.

==streamlazy:materializecache==

|{{Func|streamlazy:materializecache|$value item as item()*|item()*}}

|Returns Caches the contents of a materialized instance of the specified lazy {{Code|$valueitem}}:<br />* if an item is streamable, its value contents of lazy items will be retrieved and cachedin the item.* other, non-streamable lazy items or lazy items with cached contents will simply be passed through.Materialization Caching of a streamable value lazy items is advisable if it may the the targeted contents will not be available anymore when it will eventually be required (see the example below)at a later stage.

|In the following example, a file will be deleted before its content is returned. To avoid a “file not found” errorwhen serializing the result, the content will must be materializedcached:

let $data text := streamlazy:materializecache(file:read-text($file))return (file:delete($file), $datatext)

==streamlazy:is-streamablelazy== 

|{{Func|stream:is-streamablelazy|$item as item()|xs:boolean}}

|Checks whether the specified {{Code|$item}} is streamablelazy.|} ==lazy:is-cached== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|stream:is-cached|$item as item()|xs:boolean}}|-| '''Summary'''|Checks whether the contents of the specified {{Code|$item}} are cached. The function will always return {{Code|true}} for non-lazy items.

 * UpdateUpdated: [[#stream:materialize|stream:materialize]] extended to sequences.