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The last evaluated expression in the script (eg you don't "return val;" you just end the script "val;"), which can be a string, an object, or an array of objects is placed in a metadata field called "_PERSISTENT_".
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Preserving Metadata
The following code saves the entirety of the old document's metadata:
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Code Block |
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"onUpdateScript": "var retVal = _old_doc.metadata; retVal;"} // RESULT (IN THE CASE OF A DOCUMENT THAT DOESN'T CHANGE): { // Usual document fields "metadata": { "test1": "test", "test2": { "field": "value" }, "_PERSISTENT_": [{ "test1": "test", "test2": { "field": "value" }, }] } } |
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Generating New Metadata
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In this example, the return value will represent the delta of the two documents under comparison.
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