Balancer DOCS

Query Functions

Overview

BalancerQueries is a helper contract to provide quotes for common interactions like swaps / joins / exits without submitting a transaction.

Deployed at 0xE39B5e3B6D74016b2F6A9673D7d7493B6DF549d5 on all chains.

Etherscan

Even though Etherscan labels the query functions as write methods, they can be read through a static eth_call. This is due to nuances in how the query is crafted.

Don't use onchain queries

If you are using queryBatchSwap, queryJoin, or queryExit to calculate limits, maxAmountsIn, or minAmountsOut, this is ONLY useful if you simulate these calls OUTSIDE of the transaction you end up making. You SHOULD NOT call these functions to calculate limits from a smart contract at transaction time.

There are valid use cases for calling these functions on chain, but do not use them to determine limits.

Each query method has a section below. For reference, this snippet contains common structs / types used.

enum SwapKind { GIVEN_IN, GIVEN_OUT }

struct SingleSwap {
    bytes32 poolId;
    SwapKind kind;
    IAsset assetIn;
    IAsset assetOut;
    uint256 amount;
    bytes userData; // 0x for most swaps
}

struct FundManagement {
    address sender;
    bool fromInternalBalance;
    address payable recipient;
    bool toInternalBalance;
}

struct JoinPoolRequest {
    address[] assets,
    uint256[] maxAmountsIn,
    bytes userData,
    bool fromInternalBalance
}

struct ExitPoolRequest {
    address[] assets,
    uint256[] minAmountsOut,
    bytes userData,
    bool toInternalBalance
}

Queries

Nested Pools

Composable Stable Pools or Boosted Pools do not have join or exit functionality since those are handled as swaps! For example, if you want to figure out how much bb-a-USD you'll get for an amount of DAI, you'll need to use queryBatchSwap on a swap route that swaps DAI for bb-a-DAI and then swaps bb-a-DAI for bb-a-USD.

querySwap

querySwap(
    IVault.SingleSwap memory singleSwap,
    IVault.FundManagement memory funds)
returns (uint256)

queryBatchSwap

queryBatchSwap(
    SwapKind kind,
    BatchSwapStep[] swaps,
    IAsset[] assets,
    FundManagement funds)
returns (int256[] assetDeltas)

queryJoin

queryJoin(
    bytes32 poolId,
    address sender,
    address recipient,
    JoinPoolRequest request)
returns (uint256 bptOut, uint256[] amountsIn)

queryExit

queryExit(
    bytes32 poolId,
    address sender,
    address recipient,
    ExitPoolRequest request)
returns (uint256 bptIn, uint256[] amountsOut)