Example: Query Engine vs. Uniswap v2 Subgraph

To illustrate the differences between the subgraph and Query Engine approaches, take 24h volume on a Uniswap V2 fork:

event Swap(
    address indexed sender,
    uint amount0In, uint amount1In,
    uint amount0Out, uint amount1Out,
    address indexed to
);

Network ID	Transaction Hash	Event Emitter (Contract Address)	Event Name	Event Data (JSONB in Postgres/Query Engine)	sender	amount0In	amount1In	amount0Out	amount1Out	to
1	0xbbafabd4e4833c016c04a4ef875d8e892ed7ff7fa820532d2f09a5e86ba4f274	0xb4e16d0168e52d35cacd2c6185b44281ec28c9dc	Trade	{"sender":0x7a25.., "amount0In": 100000000000000000,"amount0Out": 163428202, "amount1Out": 0, ...}	0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D	0	100000000000000000	163428202	0	0x5083b16dA538c5022744526122243cF3BDDb3bF2
...	...	...	...	...	...	...	...	...	...	...

Query Engine with PostgreSQL

• On new protocol event
  • Decode and import into database

Reporting API

• On new protocol event
  • Rerun query for 24 hour volume

Subgraph

A rough sketch of how the Uniswap V2 subgraph will import data is as follows:

• When I get a new block (or if I have not caught up to present block)
• Fetch new block
• Run any block handlers
• Run and event log handlers
• Update a row storing the 24hr volume for a Uniswap pair

export function handleSwap(event: Swap): void {
    …
    // only accounts for volume through white listed tokens
    
    let trackedAmountUSD = getTrackedVolumeUSD(  
    amount0Total, token0 as Token, amount1Total, token1 as Token, pair as Pair)
    
     uniswapDayData.dailyVolumeUSD = uniswapDayData.dailyVolumeUSD.plus(trackedAmountUSD)
     uniswapDayData.dailyVolumeETH = uniswapDayData.dailyVolumeETH.plus(trackedAmountETH)
     uniswapDayData.dailyVolumeUntracked = uniswapDayData.dailyVolumeUntracked.plus(derivedAmountUSD)
     uniswapDayData.save()
     …
 }