Function query_memtable

datafusion-examples/examples/sql_ops/query.rs:45–80

Run a simple query against a [`MemTable`]

()

/// Run a simple query against a [`MemTable`]
pub async fn query_memtable() -> Result<()> {
    let mem_table = create_memtable()?;

    // create local execution context
    let ctx = SessionContext::new();

    // Register the in-memory table containing the data
    ctx.register_table("users", Arc::new(mem_table))?;

    // running a SQL query results in a "DataFrame", which can be used
    // to execute the query and collect the results
    let dataframe = ctx.sql("SELECT * FROM users;").await?;

    // Calling 'show' on the dataframe will execute the query and
    // print the results
    dataframe.clone().show().await?;

    // calling 'collect' on the dataframe will execute the query and
    // buffer the results into a vector of RecordBatch. There are other
    // APIs on DataFrame for incrementally generating results (e.g. streaming)
    let result = dataframe.collect().await?;

    // Use the assert_batches_eq macro to compare the results
    assert_batches_eq!(
        [
            "+----+--------------+",
            "| id | bank_account |",
            "+----+--------------+",
            "| 1  | 9000         |",
            "+----+--------------+",
        ],
        &result
    );

    Ok(())
}

fn create_memtable() -> Result<MemTable> {
    MemTable::try_new(get_schema(), vec![vec![create_record_batch()?]])