querylog: checkpoint every 8192 wal pages instead of 1000

src/storage/db.zig

@@ -754,6 +754,9 @@ 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
@@ -785,6 +788,16 @@ 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.
@@ -907,6 +920,18 @@ 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) {