Merge function field policy for my query

I need to create a field policy for my apollo query to retrieve over 1000 results. I have previously defined an update query function and need to migrate.

Query:

const liquidityRatesQuery = gql`
    query manyTimes($time: Int!) {
        reserve (id: "0xd0a1e359811322d97991e03f863a0c30c2cf029c0x88757f2f99175387ab4c6a4b3067c77a695b0349") {
            paramsHistory(orderBy: timestamp , orderDirection: asc , where: { timestamp_gt: $time }, first: 1000) {
            liquidityRate
            timestamp
            }
        }
    }
    `

const { loading, data, fetchMore } = useQuery(liquidityRatesQuery, {
        variables: {
            time: firstTimestamp
        }
    })

Old update query + fetch more:

const getAfter = (data: any) =>
    data && data.reserve.paramsHistory.length > 0
        ? data.reserve.paramsHistory[data.reserve.paramsHistory.length - 1].timestamp
        : null;

const updateQuery = (previousResult: any, { fetchMoreResult }: any) => {
        if (!fetchMoreResult) {
            return previousResult;
        }

        const previousParams = data.reserve.paramsHistory;
        const fetchMoreParams = data.reserve.paramsHistory;
    
        fetchMoreResult.reserve.paramsHistory = [...previousParams, ...fetchMoreParams];

        return { ...fetchMoreResult }
    }

useEffect(() => {
        if (data && fetchMore) {
            const after = getAfter(data)
            console.log(after)
            if(after!== null) {
                fetchMore({updateQuery, variables: {time: after}})
            }
        }
    }, [data, fetchMore, updateQuery])

Trying to work this logic into my client field policy. Currently I have:

export const client = new ApolloClient({
    uri: 'https://api.thegraph.com/subgraphs/name/aave/protocol-v2-kovan',
    cache: new InMemoryCache({
        typePolicies: {
            Reserve: {
                fields: {
                    paramsHistory: {
                        merge(existing = [], incoming: any[]) {
                            return [...existing, ...incoming]
                        }
                    }
                }
            }
        }
    })
})

Any help with this would be appreciated as I’m trying to follow the documentation but struggling. Thanks in advance!