{"id":13854,"date":"2022-11-03T13:43:33","date_gmt":"2022-11-03T20:43:33","guid":{"rendered":"https:\/\/www.couchbase.com\/blog\/?p=13854"},"modified":"2024-09-12T01:42:30","modified_gmt":"2024-09-12T08:42:30","slug":"from-n1ql-to-javascript-and-back-part-7","status":"publish","type":"post","link":"https:\/\/www.couchbase.com\/blog\/from-n1ql-to-javascript-and-back-part-7\/","title":{"rendered":"From N1QL to JavaScript and Back – Part 7: Hierarchical JavaScript Storage"},"content":{"rendered":"

In previous blogs, we covered executing N1QL (SQL++) from JavaScript\u00a0functions<\/a>, processing documents\u00a0through iterators<\/a>,\u00a0manipulating data,<\/a> handling errors<\/a>, prepared statements<\/a> and other advanced topics<\/a>. The final topic to cover is a newly added feature to 7.1 that enables JavaScript library storage options.<\/span><\/p>\n

Hierarchical JavaScript library storage<\/span><\/h2>\n

Another major change in 7.1 is the JavaScript library storage having changed from flat to hierarchical.<\/span><\/p>\n

This means that alongside global libraries, you can now have libraries created under a bucket and a scope.<\/span><\/p>\n

Global libraries are available to use as both global and scope UDFs, while scope libraries are only available to use for scope UDFs created under the same scope as the library.<\/span><\/p>\n

This means that while, by using global libraries, you can continue to treat libraries as an extension of your application, and by publishing a new library you automatically amend all its instances in different buckets and scope, if you only have been granted the manage_external_scope_functions<\/em> privilege and want to create libraries for your own use, you can.<\/span><\/p>\n

Or maybe as an application developer you may want to create scope specific implementations of certain global libraries, for instance a local instance with new code that you are implementing for the next release of your application.<\/span><\/p>\n

Manipulating libraries<\/span><\/h2>\n

The jsevaluator<\/em> REST endpoint used to manipulate libraries shown at the beginning of this blog has been extended to accept buckets and scope.<\/span><\/p>\n

This is done like so:<\/span><\/p>\n

Global library<\/strong><\/p>\n

curl -v -X POST https:\/\/localhost:8093\/evaluator\/v1\/libraries\/math -u Administrator:password -d 'function add(a, b) { let data = a + b; return data; }'<\/pre>\n
Scope library<\/strong><\/p>\n
curl -v -X POST 'https:\/\/localhost:8093\/evaluator\/v1\/libraries\/math?bucket=b1&scope=s1' -u Administrator:password -d 'function add(a, b) { let data = a + b; return data; }'<\/pre>\n
Clearly the authenticated user needs to have appropriate privileges to create libraries at each level: <\/span>manage_external_functions<\/span><\/em> for global libraries and <\/span>manage_external_scope_functions<\/span><\/em> for scope libraries.<\/span><\/p>\n
Also, the referenced bucket and scope must already exist.<\/span><\/p>\n
At the cost of repeating myself, the curl command must contain the whole library, not just any new function you may want to define: please remember that any change that you make is reflected across all UDFs using the library, and any function you may drop by mistake will potentially affect multiple scopes and UDFs, so be careful.<\/span><\/p>\n
For the avoidance of doubt, this applies to the UI too.\u00a0<\/span><\/p>\n
Referencing libraries in UDFs<\/span><\/h2>\n
All the examples of <\/span>CREATE FUNCTION<\/span> seen so far use a simple string identifier for the library, meaning that they use a global library.<\/span><\/p>\n
CREATE FUNCTION \u2026 LANGUAGE JAVASCRIPT<\/span><\/em> supports the following three formats for library names:<\/span><\/p>\n