use std::str;
use crate::{Error, Result, Statement};
/// Information about a column of a SQLite query.
#[derive(Debug)]
pub struct Column<'stmt> {
name: &'stmt str,
decl_type: Option<&'stmt str>,
}
impl Column<'_> {
/// Returns the name of the column.
#[inline]
#[must_use]
pub fn name(&self) -> &str {
self.name
}
/// Returns the type of the column (`None` for expression).
#[inline]
#[must_use]
pub fn decl_type(&self) -> Option<&str> {
self.decl_type
}
}
impl Statement<'_> {
/// Get all the column names in the result set of the prepared statement.
///
/// If associated DB schema can be altered concurrently, you should make
/// sure that current statement has already been stepped once before
/// calling this method.
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 s = self.column_name_unwrap(i);
cols.push(s);
}
cols
}
/// Return the number of columns in the result set returned by the prepared
/// statement.
///
/// If associated DB schema can be altered concurrently, you should make
/// sure that current statement has already been stepped once before
/// calling this method.
#[inline]
pub fn column_count(&self) -> usize {
self.stmt.column_count()
}
/// Check that column name reference lifetime is limited:
/// https://www.sqlite.org/c3ref/column_name.html
/// > The returned string pointer is valid...
///
/// `column_name` reference can become invalid if `stmt` is reprepared
/// (because of schema change) when `query_row` is called. So we assert
/// that a compilation error happens if this reference is kept alive:
/// ```compile_fail
/// use rusqlite::{Connection, Result};
/// fn main() -> Result<()> {
/// let db = Connection::open_in_memory()?;
/// let mut stmt = db.prepare("SELECT 1 as x")?;
/// let column_name = stmt.column_name(0)?;
/// let x = stmt.query_row([], |r| r.get::<_, i64>(0))?; // E0502
/// assert_eq!(1, x);
/// assert_eq!("x", column_name);
/// Ok(())
/// }
/// ```
#[inline]
pub(super) fn column_name_unwrap(&self, col: usize) -> &str {
// Just panic if the bounds are wrong for now, we never call this
// without checking first.
self.column_name(col).expect("Column out of bounds")
}
/// Returns the name assigned to a particular column in the result set
/// returned by the prepared statement.
///
/// If associated DB schema can be altered concurrently, you should make
/// sure that current statement has already been stepped once before
/// calling this method.
///
/// ## Failure
///
/// Returns an `Error::InvalidColumnIndex` if `idx` is outside the valid
/// column range for this row.
///
/// Panics when column name is not valid UTF-8.
#[inline]
pub fn column_name(&self, col: usize) -> Result<&str> {
self.stmt
.column_name(col)
.ok_or(Error::InvalidColumnIndex(col))
.map(|slice| {
str::from_utf8(slice.to_bytes()).expect("Invalid UTF-8 sequence in column name")
})
}
/// 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.
///
/// If associated DB schema can be altered concurrently, you should make
/// sure that current statement has already been stepped once before
/// calling this method.
///
/// # Failure
///
/// Will return an `Error::InvalidColumnName` when there is no column with
/// the specified `name`.
#[inline]
pub fn column_index(&self, name: &str) -> Result<usize> {
let bytes = name.as_bytes();
let n = self.column_count();
for i in 0..n {
// Note: `column_name` is only fallible if `i` is out of bounds,
// which we've already checked.
if bytes.eq_ignore_ascii_case(self.stmt.column_name(i).unwrap().to_bytes()) {
return Ok(i);
}
}
Err(Error::InvalidColumnName(String::from(name)))
}
/// Returns a slice describing the columns of the result of the query.
///
/// If associated DB schema can be altered concurrently, you should make
/// sure that current statement has already been stepped once before
/// calling this method.
#[cfg(feature = "column_decltype")]
#[cfg_attr(docsrs, doc(cfg(feature = "column_decltype")))]
pub fn columns(&self) -> Vec<Column> {
let n = self.column_count();
let mut cols = Vec::with_capacity(n as usize);
for i in 0..n {
let name = self.column_name_unwrap(i);
let slice = self.stmt.column_decltype(i);
let decl_type = slice.map(|s| {
str::from_utf8(s.to_bytes()).expect("Invalid UTF-8 sequence in column declaration")
});
cols.push(Column { name, decl_type });
}
cols
}
}
#[cfg(test)]
mod test {
use crate::{Connection, Result};
#[test]
#[cfg(feature = "column_decltype")]
fn test_columns() -> Result<()> {
use super::Column;
let db = Connection::open_in_memory()?;
let query = db.prepare("SELECT * FROM sqlite_master")?;
let columns = query.columns();
let column_names: Vec<&str> = columns.iter().map(Column::name).collect();
assert_eq!(
column_names.as_slice(),
&["type", "name", "tbl_name", "rootpage", "sql"]
);
let column_types: Vec<Option<String>> = columns
.iter()
.map(|col| col.decl_type().map(str::to_lowercase))
.collect();
assert_eq!(
&column_types[..3],
&[
Some("text".to_owned()),
Some("text".to_owned()),
Some("text".to_owned()),
]
);
Ok(())
}
#[test]
fn test_column_name_in_error() -> Result<()> {
use crate::{types::Type, Error};
let db = Connection::open_in_memory()?;
db.execute_batch(
"BEGIN;
CREATE TABLE foo(x INTEGER, y TEXT);
INSERT INTO foo VALUES(4, NULL);
END;",
)?;
let mut stmt = db.prepare("SELECT x as renamed, y FROM foo")?;
let mut rows = stmt.query([])?;
let row = rows.next()?.unwrap();
match row.get::<_, String>(0).unwrap_err() {
Error::InvalidColumnType(idx, name, ty) => {
assert_eq!(idx, 0);
assert_eq!(name, "renamed");
assert_eq!(ty, Type::Integer);
}
e => {
panic!("Unexpected error type: {:?}", e);
}
}
match row.get::<_, String>("y").unwrap_err() {
Error::InvalidColumnType(idx, name, ty) => {
assert_eq!(idx, 1);
assert_eq!(name, "y");
assert_eq!(ty, Type::Null);
}
e => {
panic!("Unexpected error type: {:?}", e);
}
}
Ok(())
}
/// `column_name` reference should stay valid until `stmt` is reprepared (or
/// reset) even if DB schema is altered (SQLite documentation is
/// ambiguous here because it says reference "is valid until (...) the next
/// call to sqlite3_column_name() or sqlite3_column_name16() on the same
/// column.". We assume that reference is valid if only
/// `sqlite3_column_name()` is used):
#[test]
#[cfg(feature = "modern_sqlite")]
fn test_column_name_reference() -> Result<()> {
let db = Connection::open_in_memory()?;
db.execute_batch("CREATE TABLE y (x);")?;
let stmt = db.prepare("SELECT x FROM y;")?;
let column_name = stmt.column_name(0)?;
assert_eq!("x", column_name);
db.execute_batch("ALTER TABLE y RENAME COLUMN x TO z;")?;
// column name is not refreshed until statement is re-prepared
let same_column_name = stmt.column_name(0)?;
assert_eq!(same_column_name, column_name);
Ok(())
}
}