eXist-db / XQuery compression:zip() of XML files saves text only - xquery

Question

In eXist-db 4.4, XQuery 3.1, I am using automation to compress a number of xml files. The problem is that when they compress they are storing only the text content and not the xml content.
This function uses compression:zip to create a zip from a batch of documents:
declare option exist:serialize "expand-xincludes=no";
declare option exist:serialize "method=xml media-type=application/xml";
declare function zip:create-zip-by-batch()
{
[...]
let $zipobject := compression:zip(zip:get-entry-for-zip($x,false())
let $zipname := "foozipname.zip"
let $store := xmldb:store("/db/foodirectory", $zipname, $zipobject)
return $store
};
The above calls this function, where the documents are serialized and put into <entry> per documentation:
declare option exist:serialize "expand-xincludes=no";
declare option exist:serialize "method=xml media-type=application/xml";
declare function zip:get-entry-for-zip($x)
{
[...for each $foo document in $x, create an <entry>...]
let $serialized := serialize($foo, map { "method": "xml" })
let $entry =
<entry name="somefooname" type='xml' method='store'>
{$serialized}
</entry>
[...return a sequence of $entry...]
}
I think it's missing a configuration for serialization, but I can't figure it out...
Thanks in advance for any help.

Answer 1

Here a query for eXist demonstrating how to compress XML documents into a ZIP file and store it into one's database:
xquery version "3.1";
(: create a test collection with 10 test files: 1.xml = <x>1</x>
thru 10.xml = <x>10</x> :)
let $prepare := xmldb:create-collection("/db", "test")
let $populate := (1 to 10) ! xmldb:store("/db/test", . || ".xml", <x>{.}</x>)
(: construct zip-bound <entry> elements for the documents in the test collection :)
let $entries := collection("/db/test") !
<entry name="{util:document-name(.)}" type="xml" method="store">{
serialize(., map { "method": "xml" })
}</entry>
(: compress the entries and store in database :)
let $zip := compression:zip($entries, false())
return
xmldb:store("/db", "test.zip", $zip)
The resulting ZIP file contains the 10 test XML documents, intact. For a variant showing how to write the ZIP file to a location on your file system, see https://gist.github.com/joewiz/aa8d84500b1f1478779cdf2cc1934348.
For a fuller discussion of serialization options in eXist, see my answer to an earlier question: https://stackoverflow.com/a/49290616/659732.