Optimizing IndexedDB query

Question

I am using Dexie.JS to work with IndexedDB. Currently, have a stupid query written as:

return db.events.each((element) => {
  let d = element.cause.data;
  if (d.hasOwnProperty('deleted') && (false == d.deleted) &&
      d.hasOwnProperty('abbreviation') &&
      d.hasOwnProperty('contents') && (d.abbreviation == key)) {
    snippet = d.contents;
  }
}).then(() => {
  return snippet;
});

It is working correctly, but slow as molasses on a large database. Should I run each on a collection made from db.events with applied where? Would that improve performance?

Thank you

Answer 1

Yes if assuming your "key" variable is of an indexable type: string, number, Date, TypedArray or Array, you can optimize the query like this:

First, make sure to add the index "cause.data.abbreviation" on db.events:

db.version(2).stores({
  events: 'yourPrimaryKey, cause.data.abbreviation'
});

Then, rewrite the query like this:

return db.events
  // Let indexedDB sort out all items matching given key:
  .where('cause.data.abbreviation').equals(key)
  // Filter the rest manually using Collection.filter():
  .filter(element => {
    let d = element.cause.data;
    return (d.hasOwnProperty('deleted') && (false == d.deleted) &&
      d.hasOwnProperty('contents'));
  })
  // Execute the query and only return the first match:
  .first();