Function: Advanced Self-Recursion Parameter

Enterprise Edition

Perform the Advanced Self-Recursion parameter where Eventing interacts with the Data Service.

The advancedSelfRecursion function:

Performs the Advanced Self-Recursion parameter
Requires Eventing Storage (or a metadata collection) and a source collection
Requires a binding of type bucket alias
Operates on any mutation where the meta.id or KEY starts with doquery:

For more information about the Advanced Self-Recursion parameter, see Optional { "self_recursion": true }` Parameter.

The following example shows you how to stop and restart a long-running process like a N1QL query. It counts the number of hotels that start with a particular letter.

advancedSelfRecursion
Input data
Output data
Output log

// Configure the settings for the advancedSelfRecursion function as follows:
//
// Version 7.6+
//   "Function Scope"
//     *.* (or try bulk.data if non-privileged)
//   "Listen to Location"
//     bulk.data.source
//   "Eventing Storage"
//     rr100.eventing.metadata
//   Binding(s)
//    1. "binding type", "alias name...", "bucket.scope.collection", "Access"
//       "bucket alias", "src_col",       "bulk.data.source",        "read and write"
//
//   You must have the sample dataset travel-sample installed

function OnUpdate(doc, meta) {
    if ( meta.id.startsWith("doquery:") === false ) return;
    if (doc.done && doc.done === true) return;

    if (! doc.continue)  {
        doc.queryBeg = new Date();
        doc.queryCnt = 0;
        doc.currentQueryOffset = 0;
        doc.namesProcessed = 0;
        doc.letterHash = {};
        log(meta.id,'Query initialized at ' + doc.queryBeg);
    }

    var offset = doc.currentQueryOffset;
    var results =
        SELECT name
        FROM `travel-sample`.`inventory`.`hotel`
        LIMIT 100
        OFFSET $offset;

    doc.queryCnt++;
    doc.currentQueryOffset = doc.currentQueryOffset + 100;

    var loopCnt = 0;
    for (var item of results) {
        loopCnt++;
        doc.namesProcessed++;
        var name = item.name;
        if (name && name.length > 0) {
            // Extract the first character and convert it to lowercase
            var firstChar = name[0].toLowerCase();

            // If the letter exists in the hash, increment its count. Otherwise initialize it to 1.
            if (doc.letterHash[firstChar]) {
                doc.letterHash[firstChar]++;
            } else {
                doc.letterHash[firstChar] = 1;
            }
        }
    }
    results.close();

    if (loopCnt < 100) {
        // we are done
        if (doc.continue) delete doc.continue
        doc.done = true;
        doc.queryEnd = new Date();
        log(meta.id,'Query cnt complete mutations    ' + doc.queryCnt + ' namesProcessed ' + doc.namesProcessed );
        log(meta.id,'Query completed at ' + doc.queryEnd);
        log(meta.id,'Result hotels starting with "a" ' + doc.letterHash['a'] + ', hotels starting with "b" ' + doc.letterHash['b'] + ', ...');
        // no self recursion
        src_col[meta.id] = doc;
    } else {
        // we are not done
        doc.continue = true;
        log(meta.id,'Query cnt in progress mutations ' + doc.queryCnt + ' namesProcessed ' + doc.namesProcessed );
        // using self recursion results in a continuation of the query
        couchbase.upsert(src_col, meta, doc, { "self_recursion": true });
    }
}

INPUT: KEY doquery:001

{
  "id": "doquery:001"
}

OUTPUT: KEY doquery:001
{
  "id": "doquery:001",
  "queryBeg": "2024-03-15T21:07:38.114Z",
  "queryCnt": 10,
  "currentQueryOffset": 1000,
  "namesProcessed": 917,
  "letterHash": {
    "1": 1,
    "5": 2,
    "8": 1,
    "m": 58,
    "t": 127,
    "l": 41,
    "g": 25,
    "w": 27,
    "a": 33,
    "b": 48,
    "r": 35,
    "h": 168,
    "n": 19,
    "o": 15,
    "p": 41,
    "s": 64,
    "c": 84,
    "i": 23,
    "u": 8,
    "k": 15,
    "j": 7,
    "'": 1,
    "e": 16,
    "d": 21,
    "q": 4,
    "f": 16,
    "y": 5,
    "v": 12
  },
  "done": true,
  "queryEnd": "2024-03-15T21:07:38.425Z"
}

2024-03-15T14:07:38.116-07:00 [INFO] "doquery:001" "Query initialized at Fri Mar 15 2024 14:07:38 GMT-0700 (Pacific Daylight Time)"

2024-03-15T14:07:38.159-07:00 [INFO] "doquery:001" "Query cnt in progress mutations 1 namesProcessed 100"

2024-03-15T14:07:38.175-07:00 [INFO] "doquery:001" "Query cnt in progress mutations 2 namesProcessed 200"

2024-03-15T14:07:38.191-07:00 [INFO] "doquery:001" "Query cnt in progress mutations 3 namesProcessed 300"

2024-03-15T14:07:38.204-07:00 [INFO] "doquery:001" "Query cnt in progress mutations 4 namesProcessed 400"

2024-03-15T14:07:38.217-07:00 [INFO] "doquery:001" "Query cnt in progress mutations 5 namesProcessed 500"

2024-03-15T14:07:38.351-07:00 [INFO] "doquery:001" "Query cnt in progress mutations 6 namesProcessed 600"

2024-03-15T14:07:38.376-07:00 [INFO] "doquery:001" "Query cnt in progress mutations 7 namesProcessed 700"

2024-03-15T14:07:38.396-07:00 [INFO] "doquery:001" "Query cnt in progress mutations 8 namesProcessed 800"

2024-03-15T14:07:38.413-07:00 [INFO] "doquery:001" "Query cnt in progress mutations 9 namesProcessed 900"

2024-03-15T14:07:38.425-07:00 [INFO] "doquery:001" "Query cnt complete mutations    10 namesProcessed 917"

2024-03-15T14:07:38.425-07:00 [INFO] "doquery:001" "Query completed at Fri Mar 15 2024 14:07:38 GMT-0700 (Pacific Daylight Time)"

2024-03-15T14:07:38.425-07:00 [INFO] "doquery:001" "Result hotels starting with \"a\" 33, hotels starting with \"b\" 48, ..."