Query Functions
Overview
Queries provide the ability to simulate an operation and find its result without executing a transaction. Balancer Routers provide a query for all state changing liquidity operations. An example of how this is useful can be seen when setting slippage limits.
Router queries
The detailed Router API description can be found in the Router API section.
queryAddLiquidityUnbalanced
queryAddLiquiditySingleTokenExactOut
queryAddLiquidityCustom
queryRemoveLiquidityProportional
queryRemoveLiquiditySingleTokenExactIn
queryRemoveLiquiditySingleTokenExactOut
queryRemoveLiquidityCustom
queryRemoveLiquidityCustom
queryRemoveLiquidityRecovery
querySwapSingleTokenExactIn
querySwapSingleTokenExactOut
querySwapExactIn
querySwapExactOut
Batch Router queries
The detailed Router API description can be found in the Batch Router API section.
querySwapExactIn
querySwapExactOut
Complex queries
The Router and Batch Router are primarily used as entrypoints for standard queries. However, Balancer's design allows for a more flexible querying mechanism. Any Vault operation that includes a onlyWhenUnlocked
modifier can be queried natively.
Quote
This is facilitated through a quote
mechanism. The concept of Transient Accounting enables the querying of complex Vault operations. To execute a query, the Router invokes the quote
function on the Vault.
The Vault requires that any invocation of quote
be executed as a staticcall (ensured by the query
modifier). Within the quote context, the Router has the flexibility to carry out a series of complex actions without the need to settle any debt.
quoteAndRevert
Since quote
changes the Vault state some query combinations are not possible. For example, if you wanted to quote querySwapExactIn
for POOL_A but also querySwapExactOut
for POOL_A in its initial state, you would have to use quoteAndRevert
. In this variant, the call always reverts and returns the result in the revert data (similar to the v2 mechanism).