fix(gatsby): fix incorrect intersection of filtered results

[vladar]

Description

This PR fixes a bug with query filters that occurs in a very edge case. All of the following must be true in order for you to hit this bug:

1. You must have at least one source plugin that relies on touchNode (such as gatsby-source-contentful, gatsby-source-contentstack, etc)
2. You must use multiple filters in a single query
3. Filtered results must have an intersection
4. You must start the build/develop with the warm cache
5. The stars must converge in a certain way

If all of the above is true - you will see this issue.

The problem is that we rely on node.internal.counter to perform fast intersections of filtered results here:

gatsby/packages/gatsby/src/redux/nodes.ts

Lines 1099 to 1117 in f628c38

	const counterA = nodeA.internal.counter
	const counterB = nodeB.internal.counter
	if (counterA < counterB) {
	pointerA++
	} else if (counterA > counterB) {
	pointerB++
	} else {
	// nodeA===nodeB. Make sure we didn't just add this node already.
	// Since input arrays are sorted, the same node should be grouped
	// back to back, so even if both input arrays contained the same node
	// twice, this check would prevent the result from getting duplicate nodes
	if (lastAdded !== nodeA) {
	result.push(nodeA)
	lastAdded = nodeA
	}
	pointerA++
	pointerB++
	}

And this node.internal.counter is reset when we restart the gatsby process:

gatsby/packages/gatsby/src/redux/actions/public.js

Lines 617 to 618 in f628c38

	NODE_COUNTER++
	node.internal.counter = NODE_COUNTER

So after process restart, multiple nodes may end up with the same counter and mess with filter results intersection.

[pieh]

LGTM, thanks so much for diving in this problem, reverse engineering how problem could occur and finding fix for it!

[vladar]

Published in [email protected]