Executing ECSQL with the iTwin.js Frontend

See ECSQL for the query language.

Use IModelConnection.createQueryReader for asynchronous queries. It returns an ECSqlReader immediately; consume results with for await...of, await reader.step(), or await reader.toArray(). Query execution starts when the reader is consumed, and results are fetched in batches.

The synchronous withQueryReader API is available only on the backend. See Choosing a query reader for the execution and lifetime differences.

On the frontend, only ECSQL SELECT statements can be executed. Data modification must be done through the API.

Avoid Chatty Patterns

An ECSQL query initiated from the frontend necessarily requires a round trip with the backend server. In Web Apps, round trips mean exposure to network latency, so a chunky request pattern will perform better than a chatty request pattern. If multiple queries are required to build up the desired result, consider moving the operation to the backend.

See asynchronous ECSQL query examples for bindings, iteration, and row formats.