rusqlite/src/statement.rs

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use std::{convert, fmt, mem, ptr, result, str};
use std::ffi::CStr;
use std::os::raw::{c_char, c_int, c_void};
use std::slice::from_raw_parts;
use super::ffi;
use super::{Connection, RawStatement, Result, Error, ValueRef, Row, Rows, AndThenRows, MappedRows};
use super::str_to_cstring;
use types::{ToSql, ToSqlOutput};
use row::{RowsCrateImpl, MappedRowsCrateImpl, AndThenRowsCrateImpl};
/// A prepared statement.
pub struct Statement<'conn> {
conn: &'conn Connection,
stmt: RawStatement,
}
impl<'conn> Statement<'conn> {
/// Get all the column names in the result set of the prepared statement.
pub fn column_names(&self) -> Vec<&str> {
let n = self.column_count();
let mut cols = Vec::with_capacity(n as usize);
for i in 0..n {
let slice = self.stmt.column_name(i);
let s = str::from_utf8(slice.to_bytes()).unwrap();
cols.push(s);
}
cols
}
/// Return the number of columns in the result set returned by the prepared statement.
pub fn column_count(&self) -> i32 {
self.stmt.column_count()
}
/// Returns the column index in the result set for a given column name.
///
/// If there is no AS clause then the name of the column is unspecified and may change from one
/// release of SQLite to the next.
///
/// # Failure
///
/// Will return an `Error::InvalidColumnName` when there is no column with the specified `name`.
pub fn column_index(&self, name: &str) -> Result<i32> {
let bytes = name.as_bytes();
let n = self.column_count();
for i in 0..n {
if bytes == self.stmt.column_name(i).to_bytes() {
return Ok(i);
}
}
Err(Error::InvalidColumnName(String::from(name)))
}
/// Execute the prepared statement.
///
/// On success, returns the number of rows that were changed or inserted or deleted (via
/// `sqlite3_changes`).
///
/// ## Example
///
/// ```rust,no_run
/// # use rusqlite::{Connection, Result};
/// fn update_rows(conn: &Connection) -> Result<()> {
/// let mut stmt = try!(conn.prepare("UPDATE foo SET bar = 'baz' WHERE qux = ?"));
///
/// try!(stmt.execute(&[&1i32]));
/// try!(stmt.execute(&[&2i32]));
///
/// Ok(())
/// }
/// ```
///
/// # Failure
///
/// Will return `Err` if binding parameters fails, the executed statement returns rows (in
/// which case `query` should be used instead), or the underling SQLite call fails.
pub fn execute(&mut self, params: &[&ToSql]) -> Result<c_int> {
try!(self.bind_parameters(params));
self.execute_with_bound_parameters()
}
/// Execute the prepared statement with named parameter(s). If any parameters
/// that were in the prepared statement are not included in `params`, they
/// will continue to use the most-recently bound value from a previous call
/// to `execute_named`, or `NULL` if they have never been bound.
///
/// On success, returns the number of rows that were changed or inserted or deleted (via
/// `sqlite3_changes`).
///
/// ## Example
///
/// ```rust,no_run
/// # use rusqlite::{Connection, Result};
/// fn insert(conn: &Connection) -> Result<i32> {
/// let mut stmt = try!(conn.prepare("INSERT INTO test (name) VALUES (:name)"));
/// stmt.execute_named(&[(":name", &"one")])
/// }
/// ```
///
/// # Failure
///
/// Will return `Err` if binding parameters fails, the executed statement returns rows (in
/// which case `query` should be used instead), or the underling SQLite call fails.
pub fn execute_named(&mut self, params: &[(&str, &ToSql)]) -> Result<c_int> {
try!(self.bind_parameters_named(params));
self.execute_with_bound_parameters()
}
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/// Execute an INSERT and return the ROWID.
///
/// # Note
///
/// This function is a convenience wrapper around `execute()` intended for queries that
/// insert a single item. It is possible to misuse this function in a way that it cannot
/// detect, such as by calling it on a statement which _updates_ a single item rather than
/// inserting one. Please don't do that.
///
/// # Failure
///
/// Will return `Err` if no row is inserted or many rows are inserted.
pub fn insert(&mut self, params: &[&ToSql]) -> Result<i64> {
let changes = try!(self.execute(params));
match changes {
1 => Ok(self.conn.last_insert_rowid()),
_ => Err(Error::StatementChangedRows(changes)),
}
}
/// Execute the prepared statement, returning a handle to the resulting rows.
///
/// Due to lifetime restricts, the rows handle returned by `query` does not
/// implement the `Iterator` trait. Consider using `query_map` or `query_and_then`
/// instead, which do.
///
/// ## Example
///
/// ```rust,no_run
/// # use rusqlite::{Connection, Result};
/// fn get_names(conn: &Connection) -> Result<Vec<String>> {
/// let mut stmt = try!(conn.prepare("SELECT name FROM people"));
/// let mut rows = try!(stmt.query(&[]));
///
/// let mut names = Vec::new();
/// while let Some(result_row) = rows.next() {
/// let row = try!(result_row);
/// names.push(row.get(0));
/// }
///
/// Ok(names)
/// }
/// ```
///
/// ## Failure
///
/// Will return `Err` if binding parameters fails.
pub fn query<'a>(&'a mut self, params: &[&ToSql]) -> Result<Rows<'a>> {
try!(self.bind_parameters(params));
Ok(Rows::new(self))
}
/// Execute the prepared statement with named parameter(s), returning a handle for the
/// resulting rows. If any parameters that were in the prepared statement are not included in
/// `params`, they will continue to use the most-recently bound value from a previous call to
/// `query_named`, or `NULL` if they have never been bound.
///
/// ## Example
///
/// ```rust,no_run
/// # use rusqlite::{Connection, Result};
/// fn query(conn: &Connection) -> Result<()> {
/// let mut stmt = try!(conn.prepare("SELECT * FROM test where name = :name"));
/// let mut rows = try!(stmt.query_named(&[(":name", &"one")]));
/// while let Some(row) = rows.next() {
/// // ...
/// }
/// Ok(())
/// }
/// ```
///
/// # Failure
///
/// Will return `Err` if binding parameters fails.
pub fn query_named<'a>(&'a mut self, params: &[(&str, &ToSql)]) -> Result<Rows<'a>> {
try!(self.bind_parameters_named(params));
Ok(Rows::new(self))
}
/// Executes the prepared statement and maps a function over the resulting rows, returning
/// an iterator over the mapped function results.
///
/// ## Example
///
/// ```rust,no_run
/// # use rusqlite::{Connection, Result};
/// fn get_names(conn: &Connection) -> Result<Vec<String>> {
/// let mut stmt = try!(conn.prepare("SELECT name FROM people"));
/// let rows = try!(stmt.query_map(&[], |row| row.get(0)));
///
/// let mut names = Vec::new();
/// for name_result in rows {
/// names.push(try!(name_result));
/// }
///
/// Ok(names)
/// }
/// ```
///
/// ## Failure
///
/// Will return `Err` if binding parameters fails.
pub fn query_map<'a, T, F>(&'a mut self, params: &[&ToSql], f: F) -> Result<MappedRows<'a, F>>
where F: FnMut(&Row) -> T
{
let rows = self.query(params)?;
Ok(MappedRows::new(rows, f))
}
/// Execute the prepared statement with named parameter(s), returning an iterator over the
/// result of calling the mapping function over the query's rows. If any parameters that were
/// in the prepared statement are not included in `params`, they will continue to use the
/// most-recently bound value from a previous call to `query_named`, or `NULL` if they have
/// never been bound.
///
/// ## Example
///
/// ```rust,no_run
/// # use rusqlite::{Connection, Result};
/// fn get_names(conn: &Connection) -> Result<Vec<String>> {
/// let mut stmt = try!(conn.prepare("SELECT name FROM people WHERE id = :id"));
/// let rows = try!(stmt.query_map_named(&[(":id", &"one")], |row| row.get(0)));
///
/// let mut names = Vec::new();
/// for name_result in rows {
/// names.push(try!(name_result));
/// }
///
/// Ok(names)
/// }
/// ```
///
/// ## Failure
///
/// Will return `Err` if binding parameters fails.
pub fn query_map_named<'a, T, F>(&'a mut self,
params: &[(&str, &ToSql)],
f: F)
-> Result<MappedRows<'a, F>>
where F: FnMut(&Row) -> T
{
let rows = self.query_named(params)?;
Ok(MappedRows::new(rows, f))
}
/// Executes the prepared statement and maps a function over the resulting
/// rows, where the function returns a `Result` with `Error` type implementing
/// `std::convert::From<Error>` (so errors can be unified).
///
/// # Failure
///
/// Will return `Err` if binding parameters fails.
pub fn query_and_then<'a, T, E, F>(&'a mut self,
params: &[&ToSql],
f: F)
-> Result<AndThenRows<'a, F>>
where E: convert::From<Error>,
F: FnMut(&Row) -> result::Result<T, E>
{
let rows = self.query(params)?;
Ok(AndThenRows::new(rows, f))
}
/// Execute the prepared statement with named parameter(s), returning an iterator over the
/// result of calling the mapping function over the query's rows. If any parameters that were
/// in the prepared statement are not included in `params`, they will continue to use the
/// most-recently bound value from a previous call to `query_named`, or `NULL` if they have
/// never been bound.
///
/// ## Example
///
/// ```rust,no_run
/// # use rusqlite::{Connection, Result};
/// struct Person { name: String };
///
/// fn name_to_person(name: String) -> Result<Person> {
/// // ... check for valid name
/// Ok(Person{ name: name })
/// }
///
/// fn get_names(conn: &Connection) -> Result<Vec<Person>> {
/// let mut stmt = try!(conn.prepare("SELECT name FROM people WHERE id = :id"));
/// let rows = try!(stmt.query_and_then_named(&[(":id", &"one")], |row| {
/// name_to_person(row.get(0))
/// }));
///
/// let mut persons = Vec::new();
/// for person_result in rows {
/// persons.push(try!(person_result));
/// }
///
/// Ok(persons)
/// }
/// ```
///
/// ## Failure
///
/// Will return `Err` if binding parameters fails.
pub fn query_and_then_named<'a, T, E, F>(&'a mut self,
params: &[(&str, &ToSql)],
f: F)
-> Result<AndThenRows<'a, F>>
where E: convert::From<Error>,
F: FnMut(&Row) -> result::Result<T, E>
{
let rows = self.query_named(params)?;
Ok(AndThenRows::new(rows, f))
}
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/// Return `true` if a query in the SQL statement it executes returns one or more rows
/// and `false` if the SQL returns an empty set.
pub fn exists(&mut self, params: &[&ToSql]) -> Result<bool> {
let mut rows = try!(self.query(params));
let exists = {
match rows.next() {
Some(_) => true,
None => false,
}
};
Ok(exists)
}
/// Convenience method to execute a query that is expected to return a single row.
///
/// If the query returns more than one row, all rows except the first are ignored.
///
/// # Failure
///
/// Will return `Err` if the underlying SQLite call fails.
pub fn query_row<T, F>(&mut self, params: &[&ToSql], f: F) -> Result<T>
where F: FnOnce(&Row) -> T
{
let mut rows = try!(self.query(params));
rows.get_expected_row().map(|r| f(&r))
}
/// Consumes the statement.
///
/// Functionally equivalent to the `Drop` implementation, but allows callers to see any errors
/// that occur.
///
/// # Failure
///
/// Will return `Err` if the underlying SQLite call fails.
pub fn finalize(mut self) -> Result<()> {
self.finalize_()
}
/// Return the index of an SQL parameter given its name.
///
/// # Failure
///
/// Will return Err if `name` is invalid. Will return Ok(None) if the name
/// is valid but not a bound parameter of this statement.
pub fn parameter_index(&self, name: &str) -> Result<Option<i32>> {
let c_name = try!(str_to_cstring(name));
Ok(self.stmt.bind_parameter_index(&c_name))
}
fn bind_parameters(&mut self, params: &[&ToSql]) -> Result<()> {
assert!(params.len() as c_int == self.stmt.bind_parameter_count(),
"incorrect number of parameters to query(): expected {}, got {}",
self.stmt.bind_parameter_count(),
params.len());
for (i, p) in params.iter().enumerate() {
try!(self.bind_parameter(*p, (i + 1) as c_int));
}
Ok(())
}
fn bind_parameters_named(&mut self, params: &[(&str, &ToSql)]) -> Result<()> {
for &(name, value) in params {
if let Some(i) = try!(self.parameter_index(name)) {
try!(self.bind_parameter(value, i));
} else {
return Err(Error::InvalidParameterName(name.into()));
}
}
Ok(())
}
fn bind_parameter(&self, param: &ToSql, col: c_int) -> Result<()> {
let value = try!(param.to_sql());
let ptr = unsafe { self.stmt.ptr() };
let value = match value {
ToSqlOutput::Borrowed(v) => v,
ToSqlOutput::Owned(ref v) => ValueRef::from(v),
#[cfg(feature = "blob")]
ToSqlOutput::ZeroBlob(len) => {
return self.conn
.decode_result(unsafe { ffi::sqlite3_bind_zeroblob(ptr, col, len) });
}
};
self.conn.decode_result(match value {
ValueRef::Null => unsafe { ffi::sqlite3_bind_null(ptr, col) },
ValueRef::Integer(i) => unsafe { ffi::sqlite3_bind_int64(ptr, col, i) },
ValueRef::Real(r) => unsafe { ffi::sqlite3_bind_double(ptr, col, r) },
ValueRef::Text(s) => unsafe {
let length = s.len();
if length > ::std::i32::MAX as usize {
ffi::SQLITE_TOOBIG
} else {
let c_str = try!(str_to_cstring(s));
let destructor = if length > 0 {
ffi::SQLITE_TRANSIENT()
} else {
ffi::SQLITE_STATIC()
};
ffi::sqlite3_bind_text(ptr, col, c_str.as_ptr(), length as c_int, destructor)
}
},
ValueRef::Blob(b) => unsafe {
let length = b.len();
if length > ::std::i32::MAX as usize {
ffi::SQLITE_TOOBIG
} else if length == 0 {
ffi::sqlite3_bind_zeroblob(ptr, col, 0)
} else {
ffi::sqlite3_bind_blob(ptr,
col,
b.as_ptr() as *const c_void,
length as c_int,
ffi::SQLITE_TRANSIENT())
}
},
})
}
fn execute_with_bound_parameters(&mut self) -> Result<c_int> {
let r = self.stmt.step();
self.stmt.reset();
match r {
ffi::SQLITE_DONE => {
if self.column_count() == 0 {
Ok(self.conn.changes())
} else {
Err(Error::ExecuteReturnedResults)
}
}
ffi::SQLITE_ROW => Err(Error::ExecuteReturnedResults),
_ => Err(self.conn.decode_result(r).unwrap_err()),
}
}
fn finalize_(&mut self) -> Result<()> {
let mut stmt = RawStatement::new(ptr::null_mut());
mem::swap(&mut stmt, &mut self.stmt);
self.conn.decode_result(stmt.finalize())
}
}
impl<'conn> Into<RawStatement> for Statement<'conn> {
fn into(mut self) -> RawStatement {
let mut stmt = RawStatement::new(ptr::null_mut());
mem::swap(&mut stmt, &mut self.stmt);
stmt
}
}
impl<'conn> fmt::Debug for Statement<'conn> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let sql = str::from_utf8(self.stmt.sql().to_bytes());
f.debug_struct("Statement")
.field("conn", self.conn)
.field("stmt", &self.stmt)
.field("sql", &sql)
.finish()
}
}
impl<'conn> Drop for Statement<'conn> {
#[allow(unused_must_use)]
fn drop(&mut self) {
self.finalize_();
}
}
// TODO: This trait lets us have "pub(crate)" visibility on some Statement methods. Remove this
// once pub(crate) is stable.
pub trait StatementCrateImpl<'conn> {
fn new(conn: &'conn Connection, stmt: RawStatement) -> Self;
fn value_ref(&self, col: c_int) -> ValueRef;
fn step(&self) -> Result<bool>;
fn reset(&self) -> c_int;
}
impl<'conn> StatementCrateImpl<'conn> for Statement<'conn> {
fn new(conn: &Connection, stmt: RawStatement) -> Statement {
Statement {
conn: conn,
stmt: stmt,
}
}
fn value_ref(&self, col: c_int) -> ValueRef {
let raw = unsafe { self.stmt.ptr() };
match self.stmt.column_type(col) {
ffi::SQLITE_NULL => ValueRef::Null,
ffi::SQLITE_INTEGER => {
ValueRef::Integer(unsafe { ffi::sqlite3_column_int64(raw, col) })
}
ffi::SQLITE_FLOAT => ValueRef::Real(unsafe { ffi::sqlite3_column_double(raw, col) }),
ffi::SQLITE_TEXT => {
let s = unsafe {
let text = ffi::sqlite3_column_text(raw, col);
assert!(!text.is_null(),
"unexpected SQLITE_TEXT column type with NULL data");
CStr::from_ptr(text as *const c_char)
};
// sqlite3_column_text returns UTF8 data, so our unwrap here should be fine.
let s = s.to_str().expect("sqlite3_column_text returned invalid UTF-8");
ValueRef::Text(s)
}
ffi::SQLITE_BLOB => {
let (blob, len) = unsafe {
(ffi::sqlite3_column_blob(raw, col), ffi::sqlite3_column_bytes(raw, col))
};
assert!(len >= 0,
"unexpected negative return from sqlite3_column_bytes");
if len > 0 {
assert!(!blob.is_null(),
"unexpected SQLITE_BLOB column type with NULL data");
ValueRef::Blob(unsafe { from_raw_parts(blob as *const u8, len as usize) })
} else {
// The return value from sqlite3_column_blob() for a zero-length BLOB
// is a NULL pointer.
ValueRef::Blob(&[])
}
}
_ => unreachable!("sqlite3_column_type returned invalid value"),
}
}
fn step(&self) -> Result<bool> {
match self.stmt.step() {
ffi::SQLITE_ROW => Ok(true),
ffi::SQLITE_DONE => Ok(false),
code => Err(self.conn.decode_result(code).unwrap_err()),
}
}
fn reset(&self) -> c_int {
self.stmt.reset()
}
}
#[cfg(test)]
mod test {
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use {Connection, Error, Result};
#[test]
fn test_execute_named() {
let db = Connection::open_in_memory().unwrap();
db.execute_batch("CREATE TABLE foo(x INTEGER)").unwrap();
assert_eq!(db.execute_named("INSERT INTO foo(x) VALUES (:x)", &[(":x", &1i32)]).unwrap(),
1);
assert_eq!(db.execute_named("INSERT INTO foo(x) VALUES (:x)", &[(":x", &2i32)]).unwrap(),
1);
assert_eq!(3i32,
db.query_row_named::<i32, _>("SELECT SUM(x) FROM foo WHERE x > :x",
&[(":x", &0i32)],
|r| r.get(0))
.unwrap());
}
#[test]
fn test_stmt_execute_named() {
let db = Connection::open_in_memory().unwrap();
let sql = "CREATE TABLE test (id INTEGER PRIMARY KEY NOT NULL, name TEXT NOT NULL, flag \
INTEGER)";
db.execute_batch(sql).unwrap();
let mut stmt = db.prepare("INSERT INTO test (name) VALUES (:name)").unwrap();
stmt.execute_named(&[(":name", &"one")]).unwrap();
assert_eq!(1i32,
db.query_row_named::<i32, _>("SELECT COUNT(*) FROM test WHERE name = :name",
&[(":name", &"one")],
|r| r.get(0))
.unwrap());
}
#[test]
fn test_query_named() {
let db = Connection::open_in_memory().unwrap();
let sql = r#"
CREATE TABLE test (id INTEGER PRIMARY KEY NOT NULL, name TEXT NOT NULL, flag INTEGER);
INSERT INTO test(id, name) VALUES (1, "one");
"#;
db.execute_batch(sql).unwrap();
let mut stmt = db.prepare("SELECT id FROM test where name = :name").unwrap();
let mut rows = stmt.query_named(&[(":name", &"one")]).unwrap();
let id: i32 = rows.next().unwrap().unwrap().get(0);
assert_eq!(1, id);
}
#[test]
fn test_query_map_named() {
let db = Connection::open_in_memory().unwrap();
let sql = r#"
CREATE TABLE test (id INTEGER PRIMARY KEY NOT NULL, name TEXT NOT NULL, flag INTEGER);
INSERT INTO test(id, name) VALUES (1, "one");
"#;
db.execute_batch(sql).unwrap();
let mut stmt = db.prepare("SELECT id FROM test where name = :name").unwrap();
let mut rows = stmt.query_map_named(&[(":name", &"one")], |row| {
let id: i32 = row.get(0);
2 * id
})
.unwrap();
let doubled_id: i32 = rows.next().unwrap().unwrap();
assert_eq!(2, doubled_id);
}
#[test]
fn test_query_and_then_named() {
let db = Connection::open_in_memory().unwrap();
let sql = r#"
CREATE TABLE test (id INTEGER PRIMARY KEY NOT NULL, name TEXT NOT NULL, flag INTEGER);
INSERT INTO test(id, name) VALUES (1, "one");
INSERT INTO test(id, name) VALUES (2, "one");
"#;
db.execute_batch(sql).unwrap();
let mut stmt = db.prepare("SELECT id FROM test where name = :name ORDER BY id ASC")
.unwrap();
let mut rows = stmt.query_and_then_named(&[(":name", &"one")], |row| {
let id: i32 = row.get(0);
if id == 1 {
Ok(id)
} else {
Err(Error::SqliteSingleThreadedMode)
}
})
.unwrap();
// first row should be Ok
let doubled_id: i32 = rows.next().unwrap().unwrap();
assert_eq!(1, doubled_id);
// second row should be Err
match rows.next().unwrap() {
Ok(_) => panic!("invalid Ok"),
Err(Error::SqliteSingleThreadedMode) => (),
Err(_) => panic!("invalid Err"),
}
}
#[test]
fn test_unbound_parameters_are_null() {
let db = Connection::open_in_memory().unwrap();
let sql = "CREATE TABLE test (x TEXT, y TEXT)";
db.execute_batch(sql).unwrap();
let mut stmt = db.prepare("INSERT INTO test (x, y) VALUES (:x, :y)").unwrap();
stmt.execute_named(&[(":x", &"one")]).unwrap();
let result: Option<String> =
db.query_row("SELECT y FROM test WHERE x = 'one'", &[], |row| row.get(0))
.unwrap();
assert!(result.is_none());
}
#[test]
fn test_unbound_parameters_are_reused() {
let db = Connection::open_in_memory().unwrap();
let sql = "CREATE TABLE test (x TEXT, y TEXT)";
db.execute_batch(sql).unwrap();
let mut stmt = db.prepare("INSERT INTO test (x, y) VALUES (:x, :y)").unwrap();
stmt.execute_named(&[(":x", &"one")]).unwrap();
stmt.execute_named(&[(":y", &"two")]).unwrap();
let result: String =
db.query_row("SELECT x FROM test WHERE y = 'two'", &[], |row| row.get(0))
.unwrap();
assert_eq!(result, "one");
}
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#[test]
fn test_insert() {
let db = Connection::open_in_memory().unwrap();
db.execute_batch("CREATE TABLE foo(x INTEGER UNIQUE)").unwrap();
let mut stmt = db.prepare("INSERT OR IGNORE INTO foo (x) VALUES (?)").unwrap();
assert_eq!(stmt.insert(&[&1i32]).unwrap(), 1);
assert_eq!(stmt.insert(&[&2i32]).unwrap(), 2);
match stmt.insert(&[&1i32]).unwrap_err() {
Error::StatementChangedRows(0) => (),
err => panic!("Unexpected error {}", err),
}
let mut multi = db.prepare("INSERT INTO foo (x) SELECT 3 UNION ALL SELECT 4").unwrap();
match multi.insert(&[]).unwrap_err() {
Error::StatementChangedRows(2) => (),
err => panic!("Unexpected error {}", err),
}
}
#[test]
fn test_insert_different_tables() {
// Test for https://github.com/jgallagher/rusqlite/issues/171
let db = Connection::open_in_memory().unwrap();
db.execute_batch(r"
CREATE TABLE foo(x INTEGER);
CREATE TABLE bar(x INTEGER);
")
.unwrap();
assert_eq!(db.prepare("INSERT INTO foo VALUES (10)").unwrap().insert(&[]).unwrap(),
1);
assert_eq!(db.prepare("INSERT INTO bar VALUES (10)").unwrap().insert(&[]).unwrap(),
1);
}
#[test]
fn test_exists() {
let db = Connection::open_in_memory().unwrap();
let sql = "BEGIN;
CREATE TABLE foo(x INTEGER);
INSERT INTO foo VALUES(1);
INSERT INTO foo VALUES(2);
END;";
db.execute_batch(sql).unwrap();
let mut stmt = db.prepare("SELECT 1 FROM foo WHERE x = ?").unwrap();
assert!(stmt.exists(&[&1i32]).unwrap());
assert!(stmt.exists(&[&2i32]).unwrap());
assert!(!stmt.exists(&[&0i32]).unwrap());
}
#[test]
fn test_query_row() {
let db = Connection::open_in_memory().unwrap();
let sql = "BEGIN;
CREATE TABLE foo(x INTEGER, y INTEGER);
INSERT INTO foo VALUES(1, 3);
INSERT INTO foo VALUES(2, 4);
END;";
db.execute_batch(sql).unwrap();
let mut stmt = db.prepare("SELECT y FROM foo WHERE x = ?").unwrap();
let y: Result<i64> = stmt.query_row(&[&1i32], |r| r.get(0));
assert_eq!(3i64, y.unwrap());
}
}