Source code
Revision control
Copy as Markdown
Other Tools
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
use rusqlite::{
self,
types::{FromSql, ToSql},
Connection, Params, Result as SqlResult, Row, Savepoint, Transaction, TransactionBehavior,
};
use std::iter::FromIterator;
use std::ops::Deref;
use std::time::Instant;
use crate::maybe_cached::MaybeCached;
pub struct Conn(rusqlite::Connection);
/// This trait exists so that we can use these helpers on `rusqlite::{Transaction, Connection}`.
/// Note that you must import ConnExt in order to call these methods on anything.
pub trait ConnExt {
/// The method you need to implement to opt in to all of this.
fn conn(&self) -> &Connection;
/// Set the value of the pragma on the main database. Returns the same object, for chaining.
fn set_pragma<T>(&self, pragma_name: &str, pragma_value: T) -> SqlResult<&Self>
where
T: ToSql,
Self: Sized,
{
// None == Schema name, e.g. `PRAGMA some_attached_db.something = blah`
self.conn()
.pragma_update(None, pragma_name, &pragma_value)?;
Ok(self)
}
/// Get a cached or uncached statement based on a flag.
fn prepare_maybe_cached<'conn>(
&'conn self,
sql: &str,
cache: bool,
) -> SqlResult<MaybeCached<'conn>> {
MaybeCached::prepare(self.conn(), sql, cache)
}
/// Execute all the provided statements.
fn execute_all(&self, stmts: &[&str]) -> SqlResult<()> {
let conn = self.conn();
for sql in stmts {
let r = conn.execute(sql, []);
match r {
Ok(_) => {}
// Ignore ExecuteReturnedResults error because they're pointless
// and annoying.
Err(rusqlite::Error::ExecuteReturnedResults) => {}
Err(e) => return Err(e),
}
}
Ok(())
}
/// Execute a single statement.
fn execute_one(&self, stmt: &str) -> SqlResult<()> {
self.execute_all(&[stmt])
}
/// Equivalent to `Connection::execute` but caches the statement so that subsequent
/// calls to `execute_cached` will have improved performance.
fn execute_cached<P: Params>(&self, sql: &str, params: P) -> SqlResult<usize> {
let mut stmt = self.conn().prepare_cached(sql)?;
stmt.execute(params)
}
/// Execute a query that returns a single result column, and return that result.
fn query_one<T: FromSql>(&self, sql: &str) -> SqlResult<T> {
let res: T = self.conn().query_row_and_then(sql, [], |row| row.get(0))?;
Ok(res)
}
/// Return true if a query returns any rows
fn exists<P: Params>(&self, sql: &str, params: P) -> SqlResult<bool> {
let conn = self.conn();
let mut stmt = conn.prepare(sql)?;
let exists = stmt.query(params)?.next()?.is_some();
Ok(exists)
}
/// Execute a query that returns 0 or 1 result columns, returning None
/// if there were no rows, or if the only result was NULL.
fn try_query_one<T: FromSql, P: Params>(
&self,
sql: &str,
params: P,
cache: bool,
) -> SqlResult<Option<T>>
where
Self: Sized,
{
use rusqlite::OptionalExtension;
// The outer option is if we got rows, the inner option is
// if the first row was null.
let res: Option<Option<T>> = self
.conn()
.query_row_and_then_cachable(sql, params, |row| row.get(0), cache)
.optional()?;
// go from Option<Option<T>> to Option<T>
Ok(res.unwrap_or_default())
}
/// Equivalent to `rusqlite::Connection::query_row_and_then` but allows
/// passing a flag to indicate that it's cached.
fn query_row_and_then_cachable<T, E, P, F>(
&self,
sql: &str,
params: P,
mapper: F,
cache: bool,
) -> Result<T, E>
where
Self: Sized,
P: Params,
E: From<rusqlite::Error>,
F: FnOnce(&Row<'_>) -> Result<T, E>,
{
Ok(self
.try_query_row(sql, params, mapper, cache)?
.ok_or(rusqlite::Error::QueryReturnedNoRows)?)
}
/// Helper for when you'd like to get a `Vec<T>` of all the rows returned by a
/// query that takes named arguments. See also
/// `query_rows_and_then_cached`.
fn query_rows_and_then<T, E, P, F>(&self, sql: &str, params: P, mapper: F) -> Result<Vec<T>, E>
where
Self: Sized,
P: Params,
E: From<rusqlite::Error>,
F: FnMut(&Row<'_>) -> Result<T, E>,
{
query_rows_and_then_cachable(self.conn(), sql, params, mapper, false)
}
/// Helper for when you'd like to get a `Vec<T>` of all the rows returned by a
/// query that takes named arguments.
fn query_rows_and_then_cached<T, E, P, F>(
&self,
sql: &str,
params: P,
mapper: F,
) -> Result<Vec<T>, E>
where
Self: Sized,
P: Params,
E: From<rusqlite::Error>,
F: FnMut(&Row<'_>) -> Result<T, E>,
{
query_rows_and_then_cachable(self.conn(), sql, params, mapper, true)
}
/// Like `query_rows_and_then_cachable`, but works if you want a non-Vec as a result.
/// # Example:
/// ```rust,no_run
/// # use std::collections::HashSet;
/// # use sql_support::ConnExt;
/// # use rusqlite::Connection;
/// fn get_visit_tombstones(conn: &Connection, id: i64) -> rusqlite::Result<HashSet<i64>> {
/// Ok(conn.query_rows_into(
/// "SELECT visit_date FROM moz_historyvisit_tombstones
/// WHERE place_id = :place_id",
/// &[(":place_id", &id)],
/// |row| row.get::<_, i64>(0))?)
/// }
/// ```
/// Note if the type isn't inferred, you'll have to do something gross like
/// `conn.query_rows_into::<HashSet<_>, _, _, _>(...)`.
fn query_rows_into<Coll, T, E, P, F>(&self, sql: &str, params: P, mapper: F) -> Result<Coll, E>
where
Self: Sized,
E: From<rusqlite::Error>,
F: FnMut(&Row<'_>) -> Result<T, E>,
Coll: FromIterator<T>,
P: Params,
{
query_rows_and_then_cachable(self.conn(), sql, params, mapper, false)
}
/// Same as `query_rows_into`, but caches the stmt if possible.
fn query_rows_into_cached<Coll, T, E, P, F>(
&self,
sql: &str,
params: P,
mapper: F,
) -> Result<Coll, E>
where
Self: Sized,
P: Params,
E: From<rusqlite::Error>,
F: FnMut(&Row<'_>) -> Result<T, E>,
Coll: FromIterator<T>,
{
query_rows_and_then_cachable(self.conn(), sql, params, mapper, true)
}
// This should probably have a longer name...
/// Like `query_row_and_then_cachable` but returns None instead of erroring
/// if no such row exists.
fn try_query_row<T, E, P, F>(
&self,
sql: &str,
params: P,
mapper: F,
cache: bool,
) -> Result<Option<T>, E>
where
Self: Sized,
P: Params,
E: From<rusqlite::Error>,
F: FnOnce(&Row<'_>) -> Result<T, E>,
{
let conn = self.conn();
let mut stmt = MaybeCached::prepare(conn, sql, cache)?;
let mut rows = stmt.query(params)?;
rows.next()?.map(mapper).transpose()
}
/// Caveat: This won't actually get used most of the time, and calls will
/// usually invoke rusqlite's method with the same name. See comment on
/// `UncheckedTransaction` for details (generally you probably don't need to
/// care)
fn unchecked_transaction(&self) -> SqlResult<UncheckedTransaction<'_>> {
UncheckedTransaction::new(self.conn(), TransactionBehavior::Deferred)
}
/// Begin `unchecked_transaction` with `TransactionBehavior::Immediate`. Use
/// when the first operation will be a read operation, that further writes
/// depend on for correctness.
fn unchecked_transaction_imm(&self) -> SqlResult<UncheckedTransaction<'_>> {
UncheckedTransaction::new(self.conn(), TransactionBehavior::Immediate)
}
/// Get the DB size in bytes
fn get_db_size(&self) -> Result<u32, rusqlite::Error> {
let page_count: u32 = self.query_one("SELECT * from pragma_page_count()")?;
let page_size: u32 = self.query_one("SELECT * from pragma_page_size()")?;
let freelist_count: u32 = self.query_one("SELECT * from pragma_freelist_count()")?;
Ok((page_count - freelist_count) * page_size)
}
}
impl ConnExt for Connection {
#[inline]
fn conn(&self) -> &Connection {
self
}
}
impl<'conn> ConnExt for Transaction<'conn> {
#[inline]
fn conn(&self) -> &Connection {
self
}
}
impl<'conn> ConnExt for Savepoint<'conn> {
#[inline]
fn conn(&self) -> &Connection {
self
}
}
/// rusqlite, in an attempt to save us from ourselves, needs a mutable ref to a
/// connection to start a transaction. That is a bit of a PITA in some cases, so
/// we offer this as an alternative - but the responsibility of ensuring there
/// are no concurrent transactions is on our head.
///
/// This is very similar to the rusqlite `Transaction` - it doesn't prevent
/// against nested transactions but does allow you to use an immutable
/// `Connection`.
///
/// FIXME: This currently won't actually be used most of the time, because
/// `rusqlite` added [`Connection::unchecked_transaction`] (and
/// `Transaction::new_unchecked`, which can be used to reimplement
/// `unchecked_transaction_imm`), which will be preferred in a call to
/// `c.unchecked_transaction()`, because inherent methods have precedence over
/// methods on extension traits. The exception here is that this will still be
/// used by code which takes `&impl ConnExt` (I believe it would also be used if
/// you attempted to call `unchecked_transaction()` on a non-Connection that
/// implements ConnExt, such as a `Safepoint`, `UncheckedTransaction`, or
/// `Transaction` itself, but such code is clearly broken, so is not worth
/// considering).
///
/// The difference is that `rusqlite`'s version returns a normal
/// `rusqlite::Transaction`, rather than the `UncheckedTransaction` from this
/// crate. Aside from type's name and location (and the fact that `rusqlite`'s
/// detects slightly more misuse at compile time, and has more features), the
/// main difference is: `rusqlite`'s does not track when a transaction began,
/// which unfortunatly seems to be used by the coop-transaction management in
/// places in some fashion.
///
/// There are at least two options for how to fix this:
/// 1. Decide we don't need this version, and delete it, and moving the
/// transaction timing into the coop-transaction code directly (or something
/// like this).
/// 2. Decide this difference *is* important, and rename
/// `ConnExt::unchecked_transaction` to something like
/// `ConnExt::transaction_unchecked`.
pub struct UncheckedTransaction<'conn> {
pub conn: &'conn Connection,
pub started_at: Instant,
pub finished: bool,
// we could add drop_behavior etc too, but we don't need it yet - we
// always rollback.
}
impl<'conn> UncheckedTransaction<'conn> {
/// Begin a new unchecked transaction. Cannot be nested, but this is not
/// enforced by Rust (hence 'unchecked') - however, it is enforced by
/// SQLite; use a rusqlite `savepoint` for nested transactions.
pub fn new(conn: &'conn Connection, behavior: TransactionBehavior) -> SqlResult<Self> {
let query = match behavior {
TransactionBehavior::Deferred => "BEGIN DEFERRED",
TransactionBehavior::Immediate => "BEGIN IMMEDIATE",
TransactionBehavior::Exclusive => "BEGIN EXCLUSIVE",
_ => unreachable!(),
};
conn.execute_batch(query)
.map(move |_| UncheckedTransaction {
conn,
started_at: Instant::now(),
finished: false,
})
}
/// Consumes and commits an unchecked transaction.
pub fn commit(mut self) -> SqlResult<()> {
if self.finished {
log::warn!("ignoring request to commit an already finished transaction");
return Ok(());
}
self.finished = true;
self.conn.execute_batch("COMMIT")?;
log::debug!("Transaction commited after {:?}", self.started_at.elapsed());
Ok(())
}
/// Consumes and rolls back an unchecked transaction.
pub fn rollback(mut self) -> SqlResult<()> {
if self.finished {
log::warn!("ignoring request to rollback an already finished transaction");
return Ok(());
}
self.rollback_()
}
fn rollback_(&mut self) -> SqlResult<()> {
self.finished = true;
self.conn.execute_batch("ROLLBACK")?;
Ok(())
}
fn finish_(&mut self) -> SqlResult<()> {
if self.finished || self.conn.is_autocommit() {
return Ok(());
}
self.rollback_()?;
Ok(())
}
}
impl<'conn> Deref for UncheckedTransaction<'conn> {
type Target = Connection;
#[inline]
fn deref(&self) -> &Connection {
self.conn
}
}
impl<'conn> Drop for UncheckedTransaction<'conn> {
fn drop(&mut self) {
if let Err(e) = self.finish_() {
log::warn!("Error dropping an unchecked transaction: {}", e);
}
}
}
impl<'conn> ConnExt for UncheckedTransaction<'conn> {
#[inline]
fn conn(&self) -> &Connection {
self
}
}
fn query_rows_and_then_cachable<Coll, T, E, P, F>(
conn: &Connection,
sql: &str,
params: P,
mapper: F,
cache: bool,
) -> Result<Coll, E>
where
E: From<rusqlite::Error>,
F: FnMut(&Row<'_>) -> Result<T, E>,
Coll: FromIterator<T>,
P: Params,
{
let mut stmt = conn.prepare_maybe_cached(sql, cache)?;
let iter = stmt.query_and_then(params, mapper)?;
iter.collect::<Result<Coll, E>>()
}