perf(GraphQL): Part-2: Remove unnecessary dgraph.uid : uid selections for auth queries (GRAPHQL-854)

[abhimanyusinghgaur]

We don't need to query uid for auth queries, as they always have at least one field in their selection set. This optimizes the number of touched_uids greatly, while time is not much improved here.

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This change is 

[pawanrawal]

Reviewed 6 of 6 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @abhimanyusinghgaur and @MichaelJCompton)

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graphql/resolve/query_rewriter.go, line 562 at r1 (raw file):

	addArgumentsToField(dgQuery[0], field)
	selectionAuth := addSelectionSetFrom(dgQuery[0], field, authRw)
	// we don't need to query uid for auth queries, as they always have at least one field in their

What happens if the auth rule itself queries for the id, is it added in that case?

[abhimanyusinghgaur]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @MichaelJCompton and @pawanrawal)

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graphql/resolve/query_rewriter.go, line 562 at r1 (raw file):

Previously, pawanrawal (Pawan Rawal) wrote…

What happens if the auth rule itself queries for the id, is it added in that case?

Yes, that would be added as id: uid.
These dgraph.uid : uid queries were being added in case there was no uid query already existing in that subgraph. This is useful for non-null checks in GraphQL, but not useful for auth queries.