Apollo Client Query Deduplication on Cached Object - caching

Question

I recently read an article about Apollo Client Caching on the official blog, with a screenshot
here.
According to the article, if the current query contains a cached object, along with other objects, the query will be deduplicated to only query the rest of the objects.
However, I did some testing by logging out queries on the server, which suggested that the query had not been partially deduplicated. Instead, the entire query got sent to the server.
Can anyone provide any insight on this. Thanks very much.
Test:
First query:
{
post(_id: 1) {
_id
title
}
}
Second query:
{
post(_id: 1) {
_id
title
}
author(_id: 1) {
_id
firstName
}
}
Intended outcome:
The secomd query received by the server only contains
author(_id: 1) {
_id
firstName
}
since post(_id: 1) has been cached after the first query is sent, according to the blog.
Actual outcome:
Server log: (the second query has NOT been deduplicated)
{
"operationName": null,
"variables": {},
"query": "{\n post(_id: 1) {\n _id\n title\n __typename\n
}\n}\n"
} /graphql 200 81 - 0.520 ms
{
"operationName": null,
"variables": {},
"query": "{\n post(_id: 1) {\n _id\n title\n __typename\n
}\n author(_id: 1) {\n _id\n firstName\n __typename\n }\n}\n"
} /graphql 200 140 - 0.726 ms

Answer 1

There is a subject called Query deduplication in Apollo-Client
that comes from Apollo-Link (the transport layer of Apollo-Client)
but what it does is deduplicate existing queries that are currently being fetched
Query deduplication can be useful if many components display the same data, but you don’t want to fetch that data from the server many times. It works by comparing a query to all queries currently in flight
you can read more about it here and here
But it doesn't relate so much to the cache.. I think what you're looking for is a better understanding of how cache is managed in Apollo-Client
So how is caching handled in Apollo-Client? you can find a more through article about it here from their official docs: apollo-client-caching
more specifically to your case i believe that if you would use watchQuery / query and make sure the fetchPolicy is cache-first then it might not resend the query
I hope this gives you better insight on caching in Apollo-Client