Function createAbstractMapReduce

lib/index-browser.es.js:8140–9146

* Returns an "abstract" mapreduce object of the form: * * { * query: queryFun, * viewCleanup: viewCleanupFun * } * * Arguments are: * * localDoc: string * This is for the local doc that gets saved in order to track the * "dependent" DBs and clean them up for viewCleanup. I

(localDocName, mapper, reducer, ddocValidator)

 *   indexer is invalid.
 */
function createAbstractMapReduce(localDocName, mapper, reducer, ddocValidator) {

  function tryMap(db, fun, doc) {
    // emit an event if there was an error thrown by a map function.
    // putting try/catches in a single function also avoids deoptimizations.
    try {
      fun(doc);
    } catch (e) {
      emitError(db, e, {fun, doc});
    }
  }

  function tryReduce(db, fun, keys, values, rereduce) {
    // same as above, but returning the result or an error. there are two separate
    // functions to avoid extra memory allocations since the tryCode() case is used
    // for custom map functions (common) vs this function, which is only used for
    // custom reduce functions (rare)
    try {
      return {output : fun(keys, values, rereduce)};
    } catch (e) {
      emitError(db, e, {fun, keys, values, rereduce});
      return {error: e};
    }
  }

  function sortByKeyThenValue(x, y) {
    const keyCompare = collate(x.key, y.key);
    return keyCompare !== 0 ? keyCompare : collate(x.value, y.value);
  }

  function sliceResults(results, limit, skip) {
    skip = skip || 0;
    if (typeof limit === 'number') {
      return results.slice(skip, limit + skip);
    } else if (skip > 0) {
      return results.slice(skip);
    }
    return results;
  }

  function rowToDocId(row) {
    const val = row.value;
    // Users can explicitly specify a joined doc _id, or it
    // defaults to the doc _id that emitted the key/value.
    const docId = (val && typeof val === 'object' && val._id) || row.id;
    return docId;
  }

  function readAttachmentsAsBlobOrBuffer(res) {
    for (const row of res.rows) {
      const atts = row.doc && row.doc._attachments;
      if (!atts) {
        continue;
      }
      for (const filename of Object.keys(atts)) {
        const att = atts[filename];
        atts[filename].data = b64ToBluffer(att.data, att.content_type);
      }