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Support opening local store with database on read-only filesystem (#8356)

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Previously it was not possible to open a local store when its database is on a read-only filesystem. Obviously a store on a read-only filesystem cannot be modified, but it would still be useful to be able to query it.

This change adds a new read-only setting to LocalStore. When set to true, Nix will skip operations that fail when the database is on a read-only filesystem (acquiring big-lock, schema migration, etc), and the store database will be opened in immutable mode.

Co-authored-by: Ben Radford <benradf@users.noreply.github.com>
Co-authored-by: cidkidnix <cidkidnix@protonmail.com>
Co-authored-by: Dylan Green <67574902+cidkidnix@users.noreply.github.com>
Co-authored-by: John Ericson <git@JohnEricson.me>
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
This commit is contained in:
Ben Radford 2023-06-20 10:34:09 +01:00 • committed by GitHub
parent 3910430b9d
commit 6ae35534b7
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GPG key ID: 4AEE18F83AFDEB23
9 changed files with 144 additions and 16 deletions
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23
src/libstore/sqlite.hh
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@ -11,6 +11,27 @@ struct sqlite3_stmt;
namespace nix {
enum class SQLiteOpenMode {
/**
* Open the database in read-write mode.
* If the database does not exist, it will be created.
*/
Normal,
/**
* Open the database in read-write mode.
* Fails with an error if the database does not exist.
*/
NoCreate,
/**
* Open the database in immutable mode.
* In addition to the database being read-only,
* no wal or journal files will be created by sqlite.
* Use this mode if the database is on a read-only filesystem.
* Fails with an error if the database does not exist.
*/
Immutable,
};
/**
* RAII wrapper to close a SQLite database automatically.
*/
@ -18,7 +39,7 @@ struct SQLite
{
sqlite3 * db = 0;
SQLite() { }
SQLite(const Path & path, bool create = true);
SQLite(const Path & path, SQLiteOpenMode mode = SQLiteOpenMode::Normal);
SQLite(const SQLite & from) = delete;
SQLite& operator = (const SQLite & from) = delete;
SQLite& operator = (SQLite && from) { db = from.db; from.db = 0; return *this; }