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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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9 changed files with 144 additions and 16 deletions
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11
src/libstore/sqlite.cc
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@ -1,6 +1,7 @@
#include "sqlite.hh"
#include "globals.hh"
#include "util.hh"
#include "url.hh"
#include <sqlite3.h>
@ -50,15 +51,17 @@ static void traceSQL(void * x, const char * sql)
notice("SQL<[%1%]>", sql);
};
SQLite::SQLite(const Path & path, bool create)
SQLite::SQLite(const Path & path, SQLiteOpenMode mode)
{
// useSQLiteWAL also indicates what virtual file system we need. Using
// `unix-dotfile` is needed on NFS file systems and on Windows' Subsystem
// for Linux (WSL) where useSQLiteWAL should be false by default.
const char *vfs = settings.useSQLiteWAL ? 0 : "unix-dotfile";
int flags = SQLITE_OPEN_READWRITE;
if (create) flags |= SQLITE_OPEN_CREATE;
int ret = sqlite3_open_v2(path.c_str(), &db, flags, vfs);
bool immutable = mode == SQLiteOpenMode::Immutable;
int flags = immutable ? SQLITE_OPEN_READONLY : SQLITE_OPEN_READWRITE;
if (mode == SQLiteOpenMode::Normal) flags |= SQLITE_OPEN_CREATE;
auto uri = "file:" + percentEncode(path) + "?immutable=" + (immutable ? "1" : "0");
int ret = sqlite3_open_v2(uri.c_str(), &db, SQLITE_OPEN_URI | flags, vfs);
if (ret != SQLITE_OK) {
const char * err = sqlite3_errstr(ret);
throw Error("cannot open SQLite database '%s': %s", path, err);