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//! `feature = "backup"` Online SQLite backup API. //! //! To create a [`Backup`], you must have two distinct [`Connection`]s - one //! for the source (which can be used while the backup is running) and one for //! the destination (which cannot). A [`Backup`] handle exposes three methods: //! [`step`](Backup::step) will attempt to back up a specified number of pages, //! [`progress`](Backup::progress) gets the current progress of the backup as of //! the last call to [`step`](Backup::step), and //! [`run_to_completion`](Backup::run_to_completion) will attempt to back up the //! entire source database, allowing you to specify how many pages are backed up //! at a time and how long the thread should sleep between chunks of pages. //! //! The following example is equivalent to "Example 2: Online Backup of a //! Running Database" from [SQLite's Online Backup API //! documentation](https://www.sqlite.org/backup.html). //! //! ```rust,no_run //! # use rusqlite::{backup, Connection, Result}; //! # use std::path::Path; //! # use std::time; //! //! fn backup_db<P: AsRef<Path>>( //! src: &Connection, //! dst: P, //! progress: fn(backup::Progress), //! ) -> Result<()> { //! let mut dst = Connection::open(dst)?; //! let backup = backup::Backup::new(src, &mut dst)?; //! backup.run_to_completion(5, time::Duration::from_millis(250), Some(progress)) //! } //! ``` use std::marker::PhantomData; use std::path::Path; use std::ptr; use std::os::raw::c_int; use std::thread; use std::time::Duration; use crate::ffi; use crate::error::{error_from_handle, error_from_sqlite_code}; use crate::{Connection, DatabaseName, Result}; impl Connection { /// `feature = "backup"` Back up the `name` database to the given /// destination path. /// /// If `progress` is not `None`, it will be called periodically /// until the backup completes. /// /// For more fine-grained control over the backup process (e.g., /// to sleep periodically during the backup or to back up to an /// already-open database connection), see the `backup` module. /// /// # Failure /// /// Will return `Err` if the destination path cannot be opened /// or if the backup fails. pub fn backup<P: AsRef<Path>>( &self, name: DatabaseName<'_>, dst_path: P, progress: Option<fn(Progress)>, ) -> Result<()> { use self::StepResult::{Busy, Done, Locked, More}; let mut dst = Connection::open(dst_path)?; let backup = Backup::new_with_names(self, name, &mut dst, DatabaseName::Main)?; let mut r = More; while r == More { r = backup.step(100)?; if let Some(f) = progress { f(backup.progress()); } } match r { Done => Ok(()), Busy => Err(unsafe { error_from_handle(ptr::null_mut(), ffi::SQLITE_BUSY) }), Locked => Err(unsafe { error_from_handle(ptr::null_mut(), ffi::SQLITE_LOCKED) }), More => unreachable!(), } } /// `feature = "backup"` Restore the given source path into the /// `name` database. If `progress` is not `None`, it will be /// called periodically until the restore completes. /// /// For more fine-grained control over the restore process (e.g., /// to sleep periodically during the restore or to restore from an /// already-open database connection), see the `backup` module. /// /// # Failure /// /// Will return `Err` if the destination path cannot be opened /// or if the restore fails. pub fn restore<P: AsRef<Path>, F: Fn(Progress)>( &mut self, name: DatabaseName<'_>, src_path: P, progress: Option<F>, ) -> Result<()> { use self::StepResult::{Busy, Done, Locked, More}; let src = Connection::open(src_path)?; let restore = Backup::new_with_names(&src, DatabaseName::Main, self, name)?; let mut r = More; let mut busy_count = 0i32; 'restore_loop: while r == More || r == Busy { r = restore.step(100)?; if let Some(ref f) = progress { f(restore.progress()); } if r == Busy { busy_count += 1; if busy_count >= 3 { break 'restore_loop; } thread::sleep(Duration::from_millis(100)); } } match r { Done => Ok(()), Busy => Err(unsafe { error_from_handle(ptr::null_mut(), ffi::SQLITE_BUSY) }), Locked => Err(unsafe { error_from_handle(ptr::null_mut(), ffi::SQLITE_LOCKED) }), More => unreachable!(), } } } /// `feature = "backup"` Possible successful results of calling /// [`Backup::step`]. #[derive(Copy, Clone, Debug, PartialEq, Eq)] #[non_exhaustive] pub enum StepResult { /// The backup is complete. Done, /// The step was successful but there are still more pages that need to be /// backed up. More, /// The step failed because appropriate locks could not be acquired. This is /// not a fatal error - the step can be retried. Busy, /// The step failed because the source connection was writing to the /// database. This is not a fatal error - the step can be retried. Locked, } /// `feature = "backup"` Struct specifying the progress of a backup. The /// percentage completion can be calculated as `(pagecount - remaining) / /// pagecount`. The progress of a backup is as of the last call to /// [`step`](Backup::step) - if the source database is modified after a call to /// [`step`](Backup::step), the progress value will become outdated and /// potentially incorrect. #[derive(Copy, Clone, Debug)] pub struct Progress { /// Number of pages in the source database that still need to be backed up. pub remaining: c_int, /// Total number of pages in the source database. pub pagecount: c_int, } /// `feature = "backup"` A handle to an online backup. pub struct Backup<'a, 'b> { phantom_from: PhantomData<&'a Connection>, phantom_to: PhantomData<&'b Connection>, b: *mut ffi::sqlite3_backup, } impl Backup<'_, '_> { /// Attempt to create a new handle that will allow backups from `from` to /// `to`. Note that `to` is a `&mut` - this is because SQLite forbids any /// API calls on the destination of a backup while the backup is taking /// place. /// /// # Failure /// /// Will return `Err` if the underlying `sqlite3_backup_init` call returns /// `NULL`. #[inline] pub fn new<'a, 'b>(from: &'a Connection, to: &'b mut Connection) -> Result<Backup<'a, 'b>> { Backup::new_with_names(from, DatabaseName::Main, to, DatabaseName::Main) } /// Attempt to create a new handle that will allow backups from the /// `from_name` database of `from` to the `to_name` database of `to`. Note /// that `to` is a `&mut` - this is because SQLite forbids any API calls on /// the destination of a backup while the backup is taking place. /// /// # Failure /// /// Will return `Err` if the underlying `sqlite3_backup_init` call returns /// `NULL`. pub fn new_with_names<'a, 'b>( from: &'a Connection, from_name: DatabaseName<'_>, to: &'b mut Connection, to_name: DatabaseName<'_>, ) -> Result<Backup<'a, 'b>> { let to_name = to_name.to_cstring()?; let from_name = from_name.to_cstring()?; let to_db = to.db.borrow_mut().db; let b = unsafe { let b = ffi::sqlite3_backup_init( to_db, to_name.as_ptr(), from.db.borrow_mut().db, from_name.as_ptr(), ); if b.is_null() { return Err(error_from_handle(to_db, ffi::sqlite3_errcode(to_db))); } b }; Ok(Backup { phantom_from: PhantomData, phantom_to: PhantomData, b, }) } /// Gets the progress of the backup as of the last call to /// [`step`](Backup::step). #[inline] pub fn progress(&self) -> Progress { unsafe { Progress { remaining: ffi::sqlite3_backup_remaining(self.b), pagecount: ffi::sqlite3_backup_pagecount(self.b), } } } /// Attempts to back up the given number of pages. If `num_pages` is /// negative, will attempt to back up all remaining pages. This will hold a /// lock on the source database for the duration, so it is probably not /// what you want for databases that are currently active (see /// [`run_to_completion`](Backup::run_to_completion) for a better /// alternative). /// /// # Failure /// /// Will return `Err` if the underlying `sqlite3_backup_step` call returns /// an error code other than `DONE`, `OK`, `BUSY`, or `LOCKED`. `BUSY` and /// `LOCKED` are transient errors and are therefore returned as possible /// `Ok` values. #[inline] pub fn step(&self, num_pages: c_int) -> Result<StepResult> { use self::StepResult::{Busy, Done, Locked, More}; let rc = unsafe { ffi::sqlite3_backup_step(self.b, num_pages) }; match rc { ffi::SQLITE_DONE => Ok(Done), ffi::SQLITE_OK => Ok(More), ffi::SQLITE_BUSY => Ok(Busy), ffi::SQLITE_LOCKED => Ok(Locked), _ => Err(error_from_sqlite_code(rc, None)), } } /// Attempts to run the entire backup. Will call /// [`step(pages_per_step)`](Backup::step) as many times as necessary, /// sleeping for `pause_between_pages` between each call to give the /// source database time to process any pending queries. This is a /// direct implementation of "Example 2: Online Backup of a Running /// Database" from [SQLite's Online Backup API documentation](https://www.sqlite.org/backup.html). /// /// If `progress` is not `None`, it will be called after each step with the /// current progress of the backup. Note that is possible the progress may /// not change if the step returns `Busy` or `Locked` even though the /// backup is still running. /// /// # Failure /// /// Will return `Err` if any of the calls to [`step`](Backup::step) return /// `Err`. pub fn run_to_completion( &self, pages_per_step: c_int, pause_between_pages: Duration, progress: Option<fn(Progress)>, ) -> Result<()> { use self::StepResult::{Busy, Done, Locked, More}; assert!(pages_per_step > 0, "pages_per_step must be positive"); loop { let r = self.step(pages_per_step)?; if let Some(progress) = progress { progress(self.progress()) } match r { More | Busy | Locked => thread::sleep(pause_between_pages), Done => return Ok(()), } } } } impl Drop for Backup<'_, '_> { #[inline] fn drop(&mut self) { unsafe { ffi::sqlite3_backup_finish(self.b) }; } } #[cfg(test)] mod test { use super::Backup; use crate::{Connection, DatabaseName, Result}; use std::time::Duration; #[test] fn test_backup() -> Result<()> { let src = Connection::open_in_memory()?; let sql = "BEGIN; CREATE TABLE foo(x INTEGER); INSERT INTO foo VALUES(42); END;"; src.execute_batch(sql)?; let mut dst = Connection::open_in_memory()?; { let backup = Backup::new(&src, &mut dst)?; backup.step(-1)?; } let the_answer: i64 = dst.query_row("SELECT x FROM foo", [], |r| r.get(0))?; assert_eq!(42, the_answer); src.execute_batch("INSERT INTO foo VALUES(43)")?; { let backup = Backup::new(&src, &mut dst)?; backup.run_to_completion(5, Duration::from_millis(250), None)?; } let the_answer: i64 = dst.query_row("SELECT SUM(x) FROM foo", [], |r| r.get(0))?; assert_eq!(42 + 43, the_answer); Ok(()) } #[test] fn test_backup_temp() -> Result<()> { let src = Connection::open_in_memory()?; let sql = "BEGIN; CREATE TEMPORARY TABLE foo(x INTEGER); INSERT INTO foo VALUES(42); END;"; src.execute_batch(sql)?; let mut dst = Connection::open_in_memory()?; { let backup = Backup::new_with_names(&src, DatabaseName::Temp, &mut dst, DatabaseName::Main)?; backup.step(-1)?; } let the_answer: i64 = dst.query_row("SELECT x FROM foo", [], |r| r.get(0))?; assert_eq!(42, the_answer); src.execute_batch("INSERT INTO foo VALUES(43)")?; { let backup = Backup::new_with_names(&src, DatabaseName::Temp, &mut dst, DatabaseName::Main)?; backup.run_to_completion(5, Duration::from_millis(250), None)?; } let the_answer: i64 = dst.query_row("SELECT SUM(x) FROM foo", [], |r| r.get(0))?; assert_eq!(42 + 43, the_answer); Ok(()) } #[test] fn test_backup_attached() -> Result<()> { let src = Connection::open_in_memory()?; let sql = "ATTACH DATABASE ':memory:' AS my_attached; BEGIN; CREATE TABLE my_attached.foo(x INTEGER); INSERT INTO my_attached.foo VALUES(42); END;"; src.execute_batch(sql)?; let mut dst = Connection::open_in_memory()?; { let backup = Backup::new_with_names( &src, DatabaseName::Attached("my_attached"), &mut dst, DatabaseName::Main, )?; backup.step(-1)?; } let the_answer: i64 = dst.query_row("SELECT x FROM foo", [], |r| r.get(0))?; assert_eq!(42, the_answer); src.execute_batch("INSERT INTO foo VALUES(43)")?; { let backup = Backup::new_with_names( &src, DatabaseName::Attached("my_attached"), &mut dst, DatabaseName::Main, )?; backup.run_to_completion(5, Duration::from_millis(250), None)?; } let the_answer: i64 = dst.query_row("SELECT SUM(x) FROM foo", [], |r| r.get(0))?; assert_eq!(42 + 43, the_answer); Ok(()) } }