Struct ArrowReader 

pub struct ArrowReader<'conn> { /* private fields */ }

Reads query results in Arrow IPC stream format.

ArrowReader provides methods to execute queries and receive results as Arrow IPC stream data. This is useful for integration with Arrow-based data processing pipelines.

How It Works

Internally, ArrowReader uses COPY (SELECT ...) TO STDOUT WITH (format arrowstream) to retrieve query results in Arrow format. The returned bytes are a valid Arrow IPC stream containing:

1. A schema message
2. One or more record batch messages

Example

use hyperdb_api::{ArrowReader, Connection, CreateMode, Result};

fn main() -> Result<()> {
    let conn = Connection::connect("localhost:7483", "test.hyper", CreateMode::CreateIfNotExists)?;

    // Create and populate a table
    conn.execute_command("CREATE TABLE data (id INT, value DOUBLE PRECISION)")?;
    conn.execute_command("INSERT INTO data VALUES (1, 1.5), (2, 2.5), (3, 3.5)")?;

    // Read the table as Arrow
    let reader = ArrowReader::new(&conn);
    let arrow_data = reader.table_to_arrow("data")?;

    println!("Got {} bytes of Arrow IPC data", arrow_data.len());
    Ok(())
}

Implementations

impl<'conn> ArrowReader<'conn>

pub fn new(connection: &'conn Connection) -> Self

Creates a new Arrow reader for the given connection.

pub fn query_to_arrow(&self, select_query: &str) -> Result<Vec<u8>>

Executes a SELECT query and returns results as Arrow IPC stream.

The query should be a SELECT statement. It will be wrapped in a COPY (...) TO STDOUT WITH (format arrowstream) to retrieve the results in Arrow format.

Arguments

• select_query - A SELECT query (without COPY wrapper)

Returns

Raw Arrow IPC stream bytes that can be parsed by Arrow libraries.

Example

let reader = ArrowReader::new(&conn);
let arrow_data = reader.query_to_arrow("SELECT id, name FROM users WHERE active = true")?;

Errors

• Returns crate::Error::Other if the connection is using gRPC transport (ArrowReader wraps COPY TO STDOUT, which is TCP-only).
• Returns crate::Error::Client if the server rejects the COPY (<query>) TO STDOUT WITH (format arrowstream) statement.
• Returns crate::Error::Io on transport-level I/O failures.

pub fn table_to_arrow(&self, table_name: &str) -> Result<Vec<u8>>

Exports an entire table to Arrow IPC stream format.

This is equivalent to query_to_arrow("SELECT * FROM table_name").

Arguments

• table_name - The table name (should be properly escaped if needed)

Returns

Raw Arrow IPC stream bytes containing all rows from the table.

Example

let reader = ArrowReader::new(&conn);
let arrow_data = reader.table_to_arrow("my_table")?;

Errors

See query_to_arrow.

pub fn table_columns_to_arrow( &self, table_name: &str, columns: &[&str], ) -> Result<Vec<u8>>

Exports specific columns from a table to Arrow IPC stream format.

Arguments

• table_name - The table name
• columns - Column names to export

Returns

Raw Arrow IPC stream bytes containing the specified columns.

Example

let reader = ArrowReader::new(&conn);
let arrow_data = reader.table_columns_to_arrow("users", &["id", "name", "email"])?;

Errors

See query_to_arrow.

pub fn table_filtered_to_arrow( &self, table_name: &str, where_clause: &str, ) -> Result<Vec<u8>>

Exports a table with a WHERE clause to Arrow IPC stream format.

Arguments

• table_name - The table name
• where_clause - The WHERE clause (without the “WHERE” keyword)

Returns

Raw Arrow IPC stream bytes containing filtered rows.

Example

let reader = ArrowReader::new(&conn);
let arrow_data = reader.table_filtered_to_arrow("users", "active = true")?;

Errors

See query_to_arrow.

Trait Implementations

impl<'conn> Debug for ArrowReader<'conn>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.