Add support for computed fields

[chetanmeh]

Some of the CouchDB views use computed fields for query evaluation. For e.g. view for rules computes a root namespace when namespace is a multi segment path

function (doc) {
  var PATHSEP = "/";
  var isRule = function (doc) {  return (doc.trigger !== undefined) };
  if (isRule(doc)) try {
    var ns = doc.namespace.split(PATHSEP);
    var root = ns[0];
    emit([doc.namespace, doc.updated], 1);
    if (root !== doc.namespace) {
      emit([root, doc.updated], 1);
    }
  } catch (e) {}
}

For supporting such cases in non CouchDB store we would introduce a sub document under _computed key which would be used to store such fields. This would allow us to created suitable matching indexed and also perform query against such fields

Required for Query Support #1

[chetanmeh]

Currently the computed fields are supported for following cases

Whisks

For entities stored in whisk collection following fields are computed

rootns

Root name space. This field is only generated when namespace is a path with more than 1 element

function (doc) {
  var PATHSEP = "/";
  var isRule = function (doc) {  return (doc.trigger !== undefined) };
  if (isRule(doc)) try {
    var ns = doc.namespace.split(PATHSEP);
    var root = ns[0];
    emit([doc.namespace, doc.updated], 1);
    if (root !== doc.namespace) {
      emit([root, doc.updated], 1);
    }
  } catch (e) {}
}

Activations

For activations following fields are computed

nspath

The nspath is computed based on logic in whisks-filters.v2.1.0/activations

function (doc) {
  var PATHSEP = "/";
  var isActivation = function (doc) { return (doc.activationId !== undefined) };
  var summarize = function (doc) {
    var endtime = doc.end !== 0 ? doc.end : undefined;
    return {
        namespace: doc.namespace,
         ...
      }
  };

  var pathFilter = function(doc) {
    for (i = 0; i < doc.annotations.length; i++) {
      var a = doc.annotations[i];
      if (a.key == "path") try {
          var p = a.value.split(PATHSEP);
          if (p.length == 3) {
            return p[1] + PATHSEP + doc.name;
          } else return doc.name;
      } catch (e) {
        return doc.name;
      }
    }
    return doc.name;
  }

  if (isActivation(doc)) try {
    var value = summarize(doc)
    emit([doc.namespace+PATHSEP+pathFilter(doc), doc.start], value);
  } catch (e) {}
}

deleteLogs

This field is computed based on logic in logCleanup/byDateWithLogs i.e. flag would enabled for all such activations which are not sequence

function (doc) {
  if (doc.activationId !== undefined && doc.logs && doc.logs.length > 0) try {
    var deleteLogs = true;
    for (i = 0; i < doc.annotations.length; i++) {
      var a = doc.annotations[i];
      if (a.key == "kind") {
        deleteLogs = a.value != "sequence";
        break;
      }
    }
    if (deleteLogs) {
      emit(doc.start, doc._id);
    }
  } catch (e) {}
}