Function read_memory

datafusion-examples/examples/dataframe/dataframe.rs:160–178

Use the DataFrame API to: 1. Read in-memory data.

(ctx: &SessionContext)

/// Use the DataFrame API to:
/// 1. Read in-memory data.
async fn read_memory(ctx: &SessionContext) -> Result<()> {
    // define data in memory
    let a: ArrayRef = Arc::new(StringArray::from(vec!["a", "b", "c", "d"]));
    let b: ArrayRef = Arc::new(Int32Array::from(vec![1, 10, 10, 100]));
    let batch = RecordBatch::try_from_iter(vec![("a", a), ("b", b)])?;

    // declare a table in memory. In Apache Spark API, this corresponds to createDataFrame(...).
    ctx.register_batch("t", batch)?;
    let df = ctx.table("t").await?;

    // construct an expression corresponding to "SELECT a, b FROM t WHERE b = 10" in SQL
    let filter = col("b").eq(lit(10));
    let df = df.select_columns(&["a", "b"])?.filter(filter)?;

    // print the results
    df.show().await?;

    Ok(())
}

/// Use the DataFrame API to:
/// 1. Read in-memory data.