One of the core missions of Bitquery is to provide better accessibility to blockchain data. Therefore we choose GraphQL to provide control to developers pulling data through our APIs.
We continue to make the GraphQL interface more powerful and today we introduce the support for “Expressions” in GraphQL APIs.
What is an Expression?
Expression will allow users to apply essential mathematical functions (like subtract, multiply, sum, divide) in the queries themselves. However, expression can only be applied to metrics. To learn more about metrics, please read our article explaining Bitquery query architecture.
Note: There is no standard definition of metrics, but a simple rule of thumb is Metics have a “calculate” field.
Breaking down Expressions
Check out the following query.
query GetTopGainers {
ethereum(network: bsc) {
dexTrades(
options: {desc: ["baseCurrency.name", "amount_expression"], limit: 50, limitBy: {each: "buyCurrency.name, a.b", limit: 2}}
quoteCurrency: {is: "0xbb4cdb9cbd36b01bd1cbaebf2de08d9173bc095c"}
time: {since: "2022-12-01"}
tradeAmountUsd: {gt: 10}
) {
baseCurrency {
name
address
symbol
}
tradeAmount(in: USD)
open_price: minimum(of: block, get: quote_price)
close_price: maximum(of: block, get: quote_price)
buyAmount
sellAmount
price_expression: expression(get: "close_price / open_price")
Price_expressionX2: expression(get: "price_expression * 2")
open_price_x2: expression(get: "open_price * 2")
amount_expression: expression(get: "buyAmount - sellAmount")
buyCurrency {
address
name
}
a: sellCurrency {
b: address
}
}
}
}
Now in the above query, you can see the following line
price_expression: expression(get: "close_price / open_price")
Here, we are getting “open_price” and “close_price” and then dividing “close_price” from “open_price” using “expression”.
Let’s see another example
{
ethereum {
transactions {
gasValue(calculate: sum)
coun2x: expression(get: "gasValue * 2")
}
}
}
Here you can see how we are multiplying gasValue with 2.
Allowing more than 1 field in limitby
If you want to limit results per specific field, you can use limitby. Now we have added support for more than 1 field in limitby field.
Look at the below example where we have used both buyCurrency.address, sellCurrency.address in the limitBy field. (query URL)
{
ethereum(network: ethereum) {
dexTrades(
options: {desc: ["block.height", "tradeIndex"],
limit: 10, offset: 0,
limitBy: {each: "buyCurrency.address,sellCurrency.address", limit: 1}}
date: {since: "2022-12-27", till: "2023-01-03"}
) {
block {
timestamp {
time(format: "%Y-%m-%d %H:%M:%S")
}
height
}
tradeIndex
protocol
exchange {
fullName
}
smartContract {
address {
address
annotation
}
}
buyAmount
buyCurrency {
address
symbol
}
buy_amount_usd: buyAmount(in: USD)
sellAmount
sellCurrency {
address
symbol
}
sell_amount_usd: sellAmount(in: USD)
transaction {
hash
}
}
}
}
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