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use crate::{
handles::{self, Statement},
parameter_collection::ParameterCollection,
CursorImpl, Error, Prepared,
};
use std::thread::panicking;
use widestring::{U16Str, U16String};
impl<'conn> Drop for Connection<'conn> {
fn drop(&mut self) {
if let Err(e) = self.connection.disconnect() {
// Avoid panicking, if we already have a panic. We don't want to mask the original
// error.
if !panicking() {
panic!("Unexpected error disconnecting: {:?}", e)
}
}
}
}
/// The connection handle references storage of all information about the connection to the data
/// source, including status, transaction state, and error information.
pub struct Connection<'c> {
connection: handles::Connection<'c>,
}
impl<'c> Connection<'c> {
pub(crate) fn new(connection: handles::Connection<'c>) -> Self {
Self { connection }
}
/// Executes a statement. This is the fastest way to submit an SQL statement for one-time
/// execution.
///
/// # Parameters
///
/// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;". A
/// question mark (`?`) may be used to indicate positional parameters in the statement text.
/// * `params`: Used to bind the placeholders in the statement text to argument values You can
/// use `()` to represent no parameters.
///
/// # Return
///
/// Returns `Some` if a cursor is created. If `None` is returned no cursor has been created (
/// e.g. the query came back empty). Note that an empty query may also create a cursor with zero
/// rows.
pub fn exec_direct_utf16(
&self,
query: &U16Str,
params: impl ParameterCollection,
) -> Result<Option<CursorImpl<Statement>>, Error> {
let mut stmt = self.connection.allocate_statement()?;
let paramset_size = params.parameter_set_size();
if paramset_size == 0 {
Ok(None)
} else {
// Reset parameters so we do not dereference stale once by mistake if we call
// `exec_direct`.
stmt.reset_parameters()?;
unsafe {
stmt.set_paramset_size(paramset_size)?;
// Bind new parameters passed by caller.
params.bind_parameters_to(&mut stmt)?;
stmt.exec_direct(query)?
};
// Check if a result set has been created.
if stmt.num_result_cols()? == 0 {
Ok(None)
} else {
Ok(Some(CursorImpl::new(stmt)))
}
}
}
/// Executes a prepareable statement. This is the fastest way to submit an SQL statement for
/// one-time execution.
///
/// # Parameters
///
/// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;".
/// * `params`: `?` may be used as a placeholder in the statement text. You can use `()` to
/// represent no parameters.
///
/// # Return
///
/// Returns `Some` if a cursor is created. If `None` is returned no cursor has been created (
/// e.g. the query came back empty). Note that an empty query may also create a cursor with zero
/// rows.
///
/// # Example
///
/// ```no_run
/// use odbc_api::Environment;
///
/// // I herby solemnly swear that this is the only ODBC environment in the entire process, thus
/// // making this call safe.
/// let env = unsafe {
/// Environment::new()?
/// };
///
/// let mut conn = env.connect("YourDatabase", "SA", "<YourStrong@Passw0rd>")?;
/// if let Some(cursor) = conn.execute("SELECT year, name FROM Birthdays;", ())? {
/// // Use cursor to process query results.
/// }
/// # Ok::<(), odbc_api::Error>(())
/// ```
pub fn execute(
&self,
query: &str,
params: impl ParameterCollection,
) -> Result<Option<CursorImpl<Statement>>, Error> {
let query = U16String::from_str(query);
self.exec_direct_utf16(&query, params)
}
/// Prepares an SQL statement. This is recommended for repeated execution of similar queries.
///
/// # Parameters
///
/// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;". `?`
/// may be used as a placeholder in the statement text, to be replaced with parameters during
/// execution.
pub fn prepare_utf16(&self, query: &U16Str) -> Result<Prepared, Error> {
let mut stmt = self.connection.allocate_statement()?;
stmt.prepare(query)?;
Ok(Prepared::new(stmt))
}
/// Prepares an SQL statement. This is recommended for repeated execution of similar queries.
///
/// # Parameters
///
/// * `query`: The text representation of the SQL statement. E.g. "SELECT * FROM my_table;". `?`
/// may be used as a placeholder in the statement text, to be replaced with parameters during
/// execution.
pub fn prepare(&self, query: &str) -> Result<Prepared, Error> {
let query = U16String::from_str(query);
self.prepare_utf16(&query)
}
/// Allows sending this connection to different threads. This Connection will still be only be
/// used by one thread at a time, but it must not always
/// be the same thread.
///
/// # Example
///
/// ```no_run
/// use std::thread;
/// use lazy_static::lazy_static;
/// use odbc_api::Environment;
/// lazy_static! {
/// static ref ENV: Environment = unsafe { Environment::new().unwrap() };
/// }
/// const MSSQL: &str =
/// "Driver={ODBC Driver 17 for SQL Server};\
/// Server=localhost;\
/// UID=SA;\
/// PWD=<YourStrong@Passw0rd>;\
/// ";
///
/// let conn = ENV.connect_with_connection_string("MSSQL").unwrap();
/// let conn = unsafe { conn.promote_to_send() };
/// let handle = thread::spawn(move || {
/// if let Some(cursor) = conn.execute("SELECT title FROM Movies ORDER BY year",())? {
/// // Use cursor to process results
/// }
/// Ok::<(), odbc_api::Error>(())
/// });
/// handle.join().unwrap()?;
/// # Ok::<(), odbc_api::Error>(())
/// ```
///
/// # Safety
///
/// According to the ODBC standard this should be safe. By calling this function you express your
/// trust in the implementation of the ODBC driver your application is using.
///
/// See: <https://docs.microsoft.com/en-us/sql/odbc/reference/develop-app/multithreading?view=sql-server-ver15>
///
/// This function may be removed in future versions of this crate and connections would be
/// `Send` and `Sync` out of the Box. This will require sufficient testing in which a wide
/// variety of database drivers prove to be thread safe. For now this API tries to error on the
/// side of caution, and leaves the amount of trust you want to put in the driver implementation
/// to the user. I have seen this go wrong in the past, but time certainly improved the
/// situation. At one point this will be cargo cult and Connection can be `Send` and `Sync` by
/// default (hopefully).
///
/// Note to users of `unixodbc`: You may configure the threading level to make unixodbc
/// synchronize access to the driver (and therby making them thread safe if they are not
/// thread safe by themself. This may however hurt your performancy if the driver would actually
/// be able to perform operations in parallel.
///
/// See: <https://stackoverflow.com/questions/4207458/using-unixodbc-in-a-multithreaded-concurrent-setting>
pub unsafe fn promote_to_send(self) -> force_send_sync::Send<Self> {
force_send_sync::Send::new(self)
}
/// Allows sending and using this connection from multiple different threads.
///
/// # Example
///
/// ```no_run
/// use std::thread;
/// use lazy_static::lazy_static;
/// use odbc_api::Environment;
/// lazy_static! {
/// static ref ENV: Environment = unsafe { Environment::new().unwrap() };
/// }
/// const MSSQL: &str =
/// "Driver={ODBC Driver 17 for SQL Server};\
/// Server=localhost;\
/// UID=SA;\
/// PWD=<YourStrong@Passw0rd>;\
/// ";
///
/// let conn = ENV.connect_with_connection_string("MSSQL").unwrap();
/// let conn = unsafe { conn.promote_to_send_and_sync() };
/// let handle = thread::spawn(move || {
/// if let Some(cursor) = conn.execute("SELECT title FROM Movies ORDER BY year",())? {
/// // Use cursor to process results
/// }
/// Ok::<(), odbc_api::Error>(())
/// });
/// handle.join().unwrap()?;
/// # Ok::<(), odbc_api::Error>(())
/// ```
///
/// # Safety
///
/// According to the ODBC standard this should be safe. By calling this function you express your
/// trust in the implementation of the ODBC driver your application is using.
///
/// See: <https://docs.microsoft.com/en-us/sql/odbc/reference/develop-app/multithreading?view=sql-server-ver15>
///
/// This function may be removed in future versions of this crate and connections would be
/// `Send` and `Sync` out of the Box. This will require sufficient testing in which a wide
/// variety of database drivers prove to be thread safe. For now this API tries to error on the
/// side of caution, and leaves the amount of trust you want to put in the driver implementation
/// to the user. I have seen this go wrong in the past, but time certainly improved the
/// situation. At one point this will be cargo cult and Connection can be `Send` and `Sync` by
/// default (hopefully).
///
/// Note to users of `unixodbc`: You may configure the threading level to make unixodbc
/// synchronize access to the driver (and therby making them thread safe if they are not
/// thread safe by themself. This may however hurt your performancy if the driver would actually
/// be able to perform operations in parallel.
///
/// See: <https://stackoverflow.com/questions/4207458/using-unixodbc-in-a-multithreaded-concurrent-setting>
pub unsafe fn promote_to_send_and_sync(self) -> force_send_sync::SendSync<Self> {
force_send_sync::SendSync::new(self)
}
}