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Function: genericFlatten

    March 23, 2025
    + 12

    Goal: Recursively and Generically Flatten a document for integration with a non-NOSQL RDBMS.

    • This function genericFlatten shows how a document can be flattened into a RDBMS importable record.

    • Requires Eventing Storage (or metadata collection), a "source" collection, and a "destination" collection.

    • Will operate on all documents where doc.type === "my_data_to_flatten".

    • Will write transformed or flattened documents to the destination collection with the same type and id.

    • The destination collection can be shared (or replicated via XCDR to a business partner - maybe to AWS, GCP, or Azure).

    • Will also remove the flattened document in the destination collection when the original source document is removed.

    • Note since the document is not available during an OnDelete we will filter by KEY prefix starting with "my_data_to_flatten:".

    javascript
    Copy
    // To run configure the settings for this Function, genericFlatten, as follows:
//
// Version 7.1+
//   "Function Scope"
//     *.* (or try bulk.data if non-privileged)
// Version 7.0+
//   "Listen to Location"
//     bulk.data.source
//   "Eventing Storage"
//     rr100.eventing.metadata
//   Binding(s)
//    1. "binding type", "alias name...", "bucket.scope.collection", "Access"
//       "bucket alias", "dst_col",       "bulk.data.destination",   "read and write"
//
// Version 6.X
//   "Source Bucket"
//     source
//   "MetaData Bucket"
//     metadata
//   Binding(s)
//    1. "binding type", "alias name...", "bucket",     "Access"
//       "bucket alias", "dst_col",       "destinaton", "read and write"

function deepFlatten(obj,flatDoc, path) {
    if (!obj || typeof obj !== 'object') {
        // log("terminal", path, obj);
        // remove leading "_" and store the path as a key to the terminal value
        flatDoc[path.substr(1)] = obj;
        return obj;
    }
    // process Object
    let newObj = {};
    if (Array.isArray(obj)) {
        for (var i=0; i<= obj.length; i++ ) {
            newObj[i] = deepFlatten(obj[i], flatDoc, path + "_" + i)
        }
    } else {
        Object.keys(obj).forEach((k) => {
            return newObj[k] = deepFlatten(obj[k], flatDoc, path + "_" + k);
        })
    }
    return newObj;
}

function OnUpdate(doc, meta) {
    if (doc.type !== "my_data_to_flatten") return;

    var flatDoc = {};
    deepFlatten(doc,flatDoc,"");

    // alias src_bkt to our source bucket. Since rev 6.5+ allowed to be in r/w mode
    dst_col[meta.id] = flatDoc;
}

function OnDelete(meta, options) {
    // filter
    if (!(meta.id.startsWith("my_data_to_flatten:"))) return;

    log("OnDelete expired=" + options.expired +" REM id: "+meta.id);
    try {
        delete dst_col[meta.id];
    } catch (e) {
        log("Error on delete: "+e+", id:",meta.id);
    }
}