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//! Array Virtual Table.
//!
//! Note: `rarray`, not `carray` is the name of the table valued function we
//! define.
//!
//!
//! # Example
//!
//! ```rust,no_run
//! # use rusqlite::{types::Value, Connection, Result, params};
//! # use std::rc::Rc;
//! fn example(db: &Connection) -> Result<()> {
//! // Note: This should be done once (usually when opening the DB).
//! rusqlite::vtab::array::load_module(&db)?;
//! let v = [1i64, 2, 3, 4];
//! // Note: A `Rc<Vec<Value>>` must be used as the parameter.
//! let values = Rc::new(v.iter().copied().map(Value::from).collect::<Vec<Value>>());
//! let mut stmt = db.prepare("SELECT value from rarray(?1);")?;
//! let rows = stmt.query_map([values], |row| row.get::<_, i64>(0))?;
//! for value in rows {
//! println!("{}", value?);
//! }
//! Ok(())
//! }
//! ```
use std::default::Default;
use std::marker::PhantomData;
use std::os::raw::{c_char, c_int, c_void};
use std::rc::Rc;
use crate::ffi;
use crate::types::{ToSql, ToSqlOutput, Value};
use crate::vtab::{
eponymous_only_module, Context, IndexConstraintOp, IndexInfo, VTab, VTabConnection, VTabCursor,
Values,
};
use crate::{Connection, Result};
pub(crate) const ARRAY_TYPE: *const c_char = (b"rarray\0" as *const u8).cast::<c_char>();
pub(crate) unsafe extern "C" fn free_array(p: *mut c_void) {
drop(Rc::from_raw(p as *const Vec<Value>));
}
/// Array parameter / pointer
pub type Array = Rc<Vec<Value>>;
impl ToSql for Array {
#[inline]
fn to_sql(&self) -> Result<ToSqlOutput<'_>> {
Ok(ToSqlOutput::Array(self.clone()))
}
}
/// Register the "rarray" module.
pub fn load_module(conn: &Connection) -> Result<()> {
let aux: Option<()> = None;
conn.create_module("rarray", eponymous_only_module::<ArrayTab>(), aux)
}
// Column numbers
// const CARRAY_COLUMN_VALUE : c_int = 0;
const CARRAY_COLUMN_POINTER: c_int = 1;
/// An instance of the Array virtual table
#[repr(C)]
struct ArrayTab {
/// Base class. Must be first
base: ffi::sqlite3_vtab,
}
unsafe impl<'vtab> VTab<'vtab> for ArrayTab {
type Aux = ();
type Cursor = ArrayTabCursor<'vtab>;
fn connect(
_: &mut VTabConnection,
_aux: Option<&()>,
_args: &[&[u8]],
) -> Result<(String, ArrayTab)> {
let vtab = ArrayTab {
base: ffi::sqlite3_vtab::default(),
};
Ok(("CREATE TABLE x(value,pointer hidden)".to_owned(), vtab))
}
fn best_index(&self, info: &mut IndexInfo) -> Result<()> {
// Index of the pointer= constraint
let mut ptr_idx = false;
for (constraint, mut constraint_usage) in info.constraints_and_usages() {
if !constraint.is_usable() {
continue;
}
if constraint.operator() != IndexConstraintOp::SQLITE_INDEX_CONSTRAINT_EQ {
continue;
}
if let CARRAY_COLUMN_POINTER = constraint.column() {
ptr_idx = true;
constraint_usage.set_argv_index(1);
constraint_usage.set_omit(true);
}
}
if ptr_idx {
info.set_estimated_cost(1_f64);
info.set_estimated_rows(100);
info.set_idx_num(1);
} else {
info.set_estimated_cost(2_147_483_647_f64);
info.set_estimated_rows(2_147_483_647);
info.set_idx_num(0);
}
Ok(())
}
fn open(&mut self) -> Result<ArrayTabCursor<'_>> {
Ok(ArrayTabCursor::new())
}
}
/// A cursor for the Array virtual table
#[repr(C)]
struct ArrayTabCursor<'vtab> {
/// Base class. Must be first
base: ffi::sqlite3_vtab_cursor,
/// The rowid
row_id: i64,
/// Pointer to the array of values ("pointer")
ptr: Option<Array>,
phantom: PhantomData<&'vtab ArrayTab>,
}
impl ArrayTabCursor<'_> {
fn new<'vtab>() -> ArrayTabCursor<'vtab> {
ArrayTabCursor {
base: ffi::sqlite3_vtab_cursor::default(),
row_id: 0,
ptr: None,
phantom: PhantomData,
}
}
fn len(&self) -> i64 {
match self.ptr {
Some(ref a) => a.len() as i64,
_ => 0,
}
}
}
unsafe impl VTabCursor for ArrayTabCursor<'_> {
fn filter(&mut self, idx_num: c_int, _idx_str: Option<&str>, args: &Values<'_>) -> Result<()> {
if idx_num > 0 {
self.ptr = args.get_array(0);
} else {
self.ptr = None;
}
self.row_id = 1;
Ok(())
}
fn next(&mut self) -> Result<()> {
self.row_id += 1;
Ok(())
}
fn eof(&self) -> bool {
self.row_id > self.len()
}
fn column(&self, ctx: &mut Context, i: c_int) -> Result<()> {
match i {
CARRAY_COLUMN_POINTER => Ok(()),
_ => {
if let Some(ref array) = self.ptr {
let value = &array[(self.row_id - 1) as usize];
ctx.set_result(&value)
} else {
Ok(())
}
}
}
}
fn rowid(&self) -> Result<i64> {
Ok(self.row_id)
}
}
#[cfg(test)]
mod test {
use crate::types::Value;
use crate::vtab::array;
use crate::{Connection, Result};
use std::rc::Rc;
#[test]
fn test_array_module() -> Result<()> {
let db = Connection::open_in_memory()?;
array::load_module(&db)?;
let v = vec![1i64, 2, 3, 4];
let values: Vec<Value> = v.into_iter().map(Value::from).collect();
let ptr = Rc::new(values);
{
let mut stmt = db.prepare("SELECT value from rarray(?1);")?;
let rows = stmt.query_map([&ptr], |row| row.get::<_, i64>(0))?;
assert_eq!(2, Rc::strong_count(&ptr));
let mut count = 0;
for (i, value) in rows.enumerate() {
assert_eq!(i as i64, value? - 1);
count += 1;
}
assert_eq!(4, count);
}
assert_eq!(1, Rc::strong_count(&ptr));
Ok(())
}
}