Struct QueryEngine 

pub struct QueryEngine { /* private fields */ }

High-performance SQL query engine powered by Apache DataFusion

The QueryEngine manages a DataFusion SessionContext and provides methods for registering data files and executing SQL queries with zero-copy streaming.

Implementations

impl QueryEngine

pub fn new() -> Result<Self>

Create a new query engine with default configuration

Errors

Returns an error if the session context cannot be initialized

pub async fn register_file( &mut self, file_path: &str, table_name: &str, ) -> Result<()>

Register a CSV or JSON file as a table in the query engine

The file format is automatically detected from the file extension. Supported formats: .csv, .json

Arguments

• file_path - Path to the data file
• table_name - Name to use for the table in SQL queries

Errors

Returns an error if:

• The file does not exist
• The file format is unsupported
• Schema inference fails
• Table registration fails

pub async fn execute_query(&self, sql: &str) -> Result<DataFrame>

Execute a SQL query and return the results as a DataFrame

Arguments

• sql - SQL query string to execute

Errors

Returns an error if query parsing or execution fails

pub async fn print_results(&self, dataframe: DataFrame) -> Result<()>

Execute a SQL query and print the results to stdout

Uses Arrow’s pretty printer for formatted table output with streaming to handle large result sets efficiently.

Arguments

• dataframe - The DataFrame to print

Errors

Returns an error if result collection or printing fails

Trait Implementations

impl Default for QueryEngine

fn default() -> Self

Returns the “default value” for a type.