feat: add save and has to index

src/index.zig

@@ -473,3 +473,164 @@ pub const ForeignKeySet = struct {
         return set;
     }
 
+    pub fn save(self: *const ForeignKeySet, db: *Db, table: []const u8) !void {
+        const key = try foreignKeyMetaKey(self.allocator, table);
+        defer self.allocator.free(key);
+
+        var out = std.ArrayList(u8).init(self.allocator);
+        defer out.deinit();
+        var countBuf: [4]u8 = undefined;
+        std.mem.writeInt(u32, &countBuf, @intCast(self.specs.items.len), .little);
+        try out.appendSlice(&countBuf);
+        for (self.specs.items) |spec| {
+            try appendLenPrefixed(&out, spec.field);
+            try appendLenPrefixed(&out, spec.refTable);
+            try appendLenPrefixed(&out, spec.refField);
+            try out.append(@intFromEnum(spec.onDelete));
+        }
+        try db.put(key, out.items);
+    }
+
+    pub fn has(self: *const ForeignKeySet, field: []const u8) bool {
+        return self.find(field) != null;
+    }
+
+    pub fn find(self: *const ForeignKeySet, field: []const u8) ?ForeignKeySpec {
+        for (self.specs.items) |spec| {
+            if (std.mem.eql(u8, spec.field, field)) return spec;
+        }
+        return null;
+    }
+
+    pub fn add(self: *ForeignKeySet, field: []const u8, refTable: []const u8, refField: []const u8, onDelete: OnDelete) !void {
+        if (self.has(field)) return;
+        const spec = ForeignKeySpec{
+            .field = try self.allocator.dupe(u8, field),
+            .refTable = try self.allocator.dupe(u8, refTable),
+            .refField = try self.allocator.dupe(u8, refField),
+            .onDelete = onDelete,
+        };
+        try self.specs.append(spec);
+    }
+
+    /// Returns true if a constraint on `field` was present and has been
+    /// removed.
+    pub fn remove(self: *ForeignKeySet, field: []const u8) bool {
+        for (self.specs.items, 0..) |spec, i| {
+            if (std.mem.eql(u8, spec.field, field)) {
+                self.allocator.free(spec.field);
+                self.allocator.free(spec.refTable);
+                self.allocator.free(spec.refField);
+                _ = self.specs.orderedRemove(i);
+                return true;
+            }
+        }
+        return false;
+    }
+
+    pub fn deinit(self: *ForeignKeySet) void {
+        for (self.specs.items) |spec| {
+            self.allocator.free(spec.field);
+            self.allocator.free(spec.refTable);
+            self.allocator.free(spec.refField);
+        }
+        self.specs.deinit();
+    }
+};
+
+/// One named CHECK constraint: a caller-chosen `name` (used only as the key
+/// under which the constraint can be dropped again, not part of the
+/// keyspace layout - unlike `CompositeIndexSpec.name`, no index entries are
+/// ever written for a CHECK) paired with the raw `expr.zig` predicate source
+/// text it must evaluate true against. Stored as source rather than a parsed
+/// tree because `index.zig` sits below `query.zig`/`expr.zig` in the
+/// dependency graph and knows nothing about `Predicate` - parsing happens
+/// fresh in whichever layer enforces it (`query.zig`'s `Table.put`,
+/// `txn_table.zig`'s `TableTxn.put`), the same "reparse on every use" cost
+/// `table select`/`table join` already pay for their own expr text.
+pub const CheckConstraintSpec = struct {
+    name: []u8,
+    source: []u8,
+};
+
+/// Persisted set of CHECK constraints on a table, at most one per name -
+/// same on-disk shape family as `ForeignKeySet` (own meta key, own
+/// namespace, two length-prefixed strings per entry).
+pub const CheckConstraintSet = struct {
+    allocator: Allocator,
+    specs: std.ArrayList(CheckConstraintSpec),
+
+    pub fn load(allocator: Allocator, db: *Db, table: []const u8) !CheckConstraintSet {
+        const key = try checkMetaKey(allocator, table);
+        defer allocator.free(key);
+
+        var set = CheckConstraintSet{ .allocator = allocator, .specs = std.ArrayList(CheckConstraintSpec).init(allocator) };
+        errdefer set.deinit();
+
+        const raw = try db.get(allocator, key) orelse return set;
+        defer allocator.free(raw);
+
+        var pos: usize = 0;
+        if (pos + 4 > raw.len) return error.Malformed;
+        const count = std.mem.readInt(u32, raw[pos..][0..4], .little);
+        pos += 4;
+        var i: u32 = 0;
+        while (i < count) : (i += 1) {
+            const name = try readLenPrefixed(allocator, raw, &pos);
+            errdefer allocator.free(name);
+            const source = try readLenPrefixed(allocator, raw, &pos);
+            try set.specs.append(.{ .name = name, .source = source });
+        }
+        return set;
+    }
+
+    pub fn save(self: *const CheckConstraintSet, db: *Db, table: []const u8) !void {
+        const key = try checkMetaKey(self.allocator, table);
+        defer self.allocator.free(key);
+
+        var out = std.ArrayList(u8).init(self.allocator);
+        defer out.deinit();
+        var countBuf: [4]u8 = undefined;
+        std.mem.writeInt(u32, &countBuf, @intCast(self.specs.items.len), .little);
+        try out.appendSlice(&countBuf);
+        for (self.specs.items) |spec| {
+            try appendLenPrefixed(&out, spec.name);
+            try appendLenPrefixed(&out, spec.source);
+        }
+        try db.put(key, out.items);
+    }
+
+    pub fn has(self: *const CheckConstraintSet, name: []const u8) bool {
+        return self.find(name) != null;
+    }
+
+    pub fn find(self: *const CheckConstraintSet, name: []const u8) ?CheckConstraintSpec {
+        for (self.specs.items) |spec| {
+            if (std.mem.eql(u8, spec.name, name)) return spec;
+        }
+        return null;
+    }
+
+    pub fn add(self: *CheckConstraintSet, name: []const u8, source: []const u8) !void {
+        if (self.has(name)) return;
+        const spec = CheckConstraintSpec{
+            .name = try self.allocator.dupe(u8, name),
+            .source = try self.allocator.dupe(u8, source),
+        };
+        try self.specs.append(spec);
+    }
+
+    /// Returns true if a constraint named `name` was present and has been
+    /// removed.
+    pub fn remove(self: *CheckConstraintSet, name: []const u8) bool {
+        for (self.specs.items, 0..) |spec, i| {
+            if (std.mem.eql(u8, spec.name, name)) {
+                self.allocator.free(spec.name);
+                self.allocator.free(spec.source);
+                _ = self.specs.orderedRemove(i);
+                return true;
+            }
+        }
+        return false;
+    }
+