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querylog: return to the default checkpoint cadence

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mokhtar
2026-08-22 23:10:17 +02:00
parent 7e0df5fd94
commit 5da4652e89
7 changed files with 4 additions and 132 deletions
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src/storage/db.zig
-25
View File
@@ -755,9 +755,6 @@ pub const Pragmas = struct {
journal_wal: bool = true,
synchronous_normal: bool = true,
foreign_keys: bool = true,
/// Null leaves SQLite's 1000-page default. A caller that sets it owns the
/// durability consequences, which depend on what the database holds.
wal_autocheckpoint_pages: ?i32 = null,
};
/// MUST be called before any transaction is opened: `PRAGMA foreign_keys` is a
@@ -789,16 +786,6 @@ pub fn applyPragmas(self: *Db, p: Pragmas) Error!void {
return error.SqliteError;
}
}
if (p.wal_autocheckpoint_pages) |pages| {
var buf: [64]u8 = undefined;
const sql = std.fmt.bufPrintZ(&buf, "PRAGMA wal_autocheckpoint = {d};", .{pages}) catch unreachable;
try self.exec(sql);
const applied = try self.queryInt("PRAGMA wal_autocheckpoint");
if (applied != pages) {
log.warn("PRAGMA wal_autocheckpoint = {d} reported {d}", .{ pages, applied });
return error.SqliteError;
}
}
}
/// A write transaction.
@@ -1052,18 +1039,6 @@ test "applyPragmas succeeds and foreign_keys reads back as 1" {
try testing.expectEqual(@as(i64, 1), try db.queryInt("PRAGMA foreign_keys"));
}
test "applyPragmas leaves wal_autocheckpoint at the default unless a page count is given" {
var db = try openMemory();
defer db.close();
try applyPragmas(&db, .{});
try testing.expectEqual(@as(i64, 1000), try db.queryInt("PRAGMA wal_autocheckpoint"));
var configured = try openMemory();
defer configured.close();
try applyPragmas(&configured, .{ .wal_autocheckpoint_pages = 8192 });
try testing.expectEqual(@as(i64, 8192), try configured.queryInt("PRAGMA wal_autocheckpoint"));
}
test "open on a directory path returns error.CantOpen and leaks no handle" {
var i: usize = 0;
while (i < 1000) : (i += 1) {
src/storage/querylog_schema.zig
+2 -27
View File
@@ -92,31 +92,6 @@ pub const fingerprint: i32 = blk: {
const set_user_version = std.fmt.comptimePrint("PRAGMA user_version = {d};", .{fingerprint});
/// The WAL checkpoint threshold for every read-write `querylog.db` connection,
/// in pages (32 MiB at the 4096-byte page size). SQLite's 1000-page default
/// trips every ~40 min under this workload and rewrites the same hot index and
/// interior pages into the main database each time; 8192 stretches that to ~5 h
/// and cuts those in-place rewrites ~8x, which is SD-card write wear this
/// household appliance does not need to spend.
///
/// The durability consequence, stated precisely:
///
/// - Commit never fsyncs at `synchronous = NORMAL`; the checkpoint's fsync is
/// the only guaranteed durability boundary. This moves that boundary from
/// ~40 min to ~5 h of querylog data under power loss or kernel panic.
/// Typical loss stays far smaller because of kernel writeback, but that is
/// not a guarantee.
/// - Process crash or clean stop loses nothing committed, at any threshold.
/// Consistency is never at risk: recovery replays the longest valid WAL
/// prefix atomically.
/// - 32 MiB is an expectation, not a cap: a pinned reader snapshot stops a
/// passive checkpoint partway and the WAL overshoots until that reader
/// finishes. The daily retention `wal_checkpoint(TRUNCATE)` is the backstop
/// that shrinks the file.
///
/// `config.db` keeps the SQLite default: it holds configuration, not a log.
pub const wal_autocheckpoint_pages: i32 = 8192;
/// Long enough for any path this program will be handed, plus the aside suffix.
/// A longer path is `error.NameTooLong`, which is what the filesystem calls
/// would have returned anyway.
@@ -166,7 +141,7 @@ pub fn open(io: std.Io, dir: std.Io.Dir, path: [:0]const u8) Error!OpenResult {
break :probe recreatable(e) orelse return e;
const opened = &handle.?;
db.applyPragmas(opened, .{ .wal_autocheckpoint_pages = wal_autocheckpoint_pages }) catch |e|
db.applyPragmas(opened, .{}) catch |e|
break :probe recreatable(e) orelse return e;
const healthy = quickCheck(opened) catch |e|
@@ -290,7 +265,7 @@ fn deleteSidecars(io: std.Io, dir: std.Io.Dir, path: []const u8) Error!void {
fn createFresh(path: [:0]const u8) db.Error!db.Db {
var database = try db.Db.open(path, .{ .mode = .read_write_create });
errdefer database.close();
try db.applyPragmas(&database, .{ .wal_autocheckpoint_pages = wal_autocheckpoint_pages });
try db.applyPragmas(&database, .{});
var tx = try db.Tx.begin(&database);
errdefer tx.rollback();
src/storage/storage_integration_test.zig
-30
View File
@@ -600,36 +600,6 @@ test "S7 case 23: a locked querylog propagates Busy and is never destroyed" {
try testing.expectEqual(@as(usize, 0), asides_after.items.items.len);
}
// ---------------------------------------------------------------------------
// the querylog checkpoint threshold (specs/querylog-autocheckpoint.md)
// ---------------------------------------------------------------------------
test "every querylog connection carries the raised wal_autocheckpoint; config.db keeps the default" {
if (!build_options.integration) return error.SkipZigTest;
var f: Fixture = .init();
defer f.deinit();
var data = try openMigrated(&f, "data");
defer data.deinit();
var opened = try data.dir.openQuerylogDb(io);
defer opened.database.close();
try testing.expectEqual(
@as(i64, querylog_schema.wal_autocheckpoint_pages),
try opened.database.queryInt("PRAGMA wal_autocheckpoint"),
);
var reopened = try data.dir.reopenQuerylogDb(io);
defer reopened.close();
try testing.expectEqual(
@as(i64, querylog_schema.wal_autocheckpoint_pages),
try reopened.queryInt("PRAGMA wal_autocheckpoint"),
);
try testing.expectEqual(@as(i64, 1000), try data.database.queryInt("PRAGMA wal_autocheckpoint"));
}
// ---------------------------------------------------------------------------
// case 8-10: config.db, permissions and the schema stamp
// ---------------------------------------------------------------------------