Feature/custom resolve field

[emaciel10]

We are looking for the ability to cache certain execute operations, specifically the resolveField calls for a large and complex resolvers that can run very frequently since they currently trigger on GraphQL subscriptions.
We have built out that caching logic in our own codebase but currently have no place to make use of this cache since the resolveField function is not currently exported.

This is a first pass attempt at adding a bit more flexibility to graphql-js execution allowing us to cache the specific resolveField results that are important to our server while still falling back on the standard resolveField function for any paths that we know do not need caching.

It is very possible that this is already achievable with graphql-js but after looking through the logic in execute.js I did not see any way of achieving this without providing some kind of optional custom resolve field function.

The main goal here is to help us address some performance concerns that have been previously raised here #723 by adding in some custom application specific caching where it seemed the most expensive operations were being repeatedly performed.

If there is another way of achieving this custom caching behavior I would really love to see if we could make it work with our current use case!

Here is a code snippet from our custom-resolve-field.ts file that illustrates a basic example of our caching logic:

import { resolveField } from 'graphql/execution/execute';
import TTLCacheMap from '../utils/ttl-cache-map';

const schemaWeakMap = new WeakMap<any, any>();

export const customResolveField: typeof resolveField = (
  exeContext,
  parentType,
  source,
  fieldNodes,
  path
) => {
  if (path.key === 'doc' && source.doc) {
    let cachedDocResolves = schemaWeakMap.get(exeContext.schema);
    if (!cachedDocResolves) {
      cachedDocResolves = new TTLCacheMap(0);
      schemaWeakMap.set(exeContext.schema, cachedDocResolves);
    }
    const cachedRes = cachedDocResolves.get(source.doc._id);
    if (cachedRes) {
      return cachedRes;
    }

    const result = resolveField(exeContext, parentType, source, fieldNodes, path);
    cachedDocResolves.set(source.doc._id, result);
    return result;
  }

  return resolveField(exeContext, parentType, source, fieldNodes, path);
};

[IvanGoncharov]

@emaciel10 Thanks for the PR 👍
From your code example, it looks like you need to cache only doc fields.
Can you just do something like this? (not tested)

for (const type of Object.values(schema.getTypeMap())) {
  if (isObjectType(type)) {
    for (const [name, field] of Object.entries(type.getFields())) {
      if (name === 'doc') {
        const oldResolve = field.resolve;
        field.resolve = (...args) => {
          const source = args[0];
          // ...
          return oldResolve(...args);
        }
      }
    }
  }
}

[emaciel10]

Hey Ivan, thanks for the suggestion, I'll take a look and see if we can override the resolve to drop in our custom caching at that level instead!

[yaacovCR]

Closing due to inactivity. Please feel free to reopen as necessary.