Create helper utils in sql pkg

src/sql/lib.zig

@@ -1,4 +1,5 @@
 const std = @import("std");
+const util = @import("util");
 
 const postgres = @import("./postgres.zig");
 const sqlite = @import("./sqlite.zig");
@@ -19,40 +20,66 @@ pub const Config = union(Type) {
 };
 
 //pub const OpenError = sqlite.OpenError | postgres.OpenError;
-
-// Represents a set of results.
-// row() must be called until it returns null, or the query may not complete
-// Must be deallocated by a call to finish()
-pub const Results = union(Type) {
+const RawResults = union(Type) {
     postgres: postgres.Results,
     sqlite: sqlite.Results,
 
-    pub fn finish(self: Results) void {
+    fn finish(self: RawResults) void {
         switch (self) {
             .postgres => |pg| pg.finish(),
             .sqlite => |lite| lite.finish(),
         }
     }
+};
+
+// Represents a set of results.
+// row() must be called until it returns null, or the query may not complete
+// Must be deallocated by a call to finish()
+pub fn Results(comptime result_types: []const type) type {
+    return struct {
+        const Self = @This();
+        const RowTuple = std.meta.Tuple(result_types);
+
+        underlying: RawResults,
+
+        pub fn finish(self: Self) void {
+            self.underlying.finish();
+        }
 
         // can be used as an optimization to reduce memory reallocation
         // only works on postgres
-    pub fn rowCount(self: Results) ?usize {
-        return switch (self) {
+        pub fn rowCount(self: Self) ?usize {
+            return switch (self.underlying) {
                 .postgres => |pg| pg.rowCount(),
                 .sqlite => null, // not possible without repeating the query
             };
         }
 
-    pub fn row(self: *Results) !?Row {
-        return switch (self.*) {
-            .postgres => |*pg| if (try pg.row()) |r| Row{ .postgres = r } else null,
-            .sqlite => |*lite| if (try lite.row()) |r| Row{ .sqlite = r } else null,
-        };
-    }
+        pub fn row(self: *Self, alloc: ?Allocator) !?RowTuple {
+            const row_val = switch (self.underlying) {
+                .postgres => |*pg| if (try pg.row()) |r| Row{ .postgres = r } else return null,
+                .sqlite => |*lite| if (try lite.row()) |r| Row{ .sqlite = r } else return null,
             };
 
+            var result: RowTuple = undefined;
+            var fields_allocated = [_]bool{false} ** result.len;
+            errdefer {
+                inline for (result_types) |_, i| {
+                    if (fields_allocated[i]) util.deepFree(alloc, result[i]);
+                }
+            }
+            inline for (result_types) |T, i| {
+                result[i] = try row_val.get(T, i, alloc);
+                fields_allocated[i] = true;
+            }
+
+            return result;
+        }
+    };
+}
+
 // Row is invalidated by the next call to result.row()
-pub const Row = union(Type) {
+const Row = union(Type) {
     postgres: postgres.Row,
     sqlite: sqlite.Row,
 
@@ -60,7 +87,7 @@ pub const Row = union(Type) {
     // Not all types require an allocator to be present. If an allocator is needed but
     // not required, it will return error.AllocatorRequired.
     // The caller is responsible for deallocating T, if relevant.
-    pub fn get(self: Row, comptime T: type, idx: u15, alloc: ?Allocator) !T {
+    fn get(self: Row, comptime T: type, idx: u15, alloc: ?Allocator) anyerror!T {
         return switch (self) {
             .postgres => |pg| pg.get(T, idx, alloc),
             .sqlite => |lite| lite.get(T, idx, alloc),
@@ -68,31 +95,181 @@ pub const Row = union(Type) {
     }
 };
 
-pub const Db = union(Type) {
+const DbUnion = union(Type) {
     postgres: postgres.Db,
     sqlite: sqlite.Db,
+};
 
+pub const Db = struct {
+    underlying: DbUnion,
     pub fn open(cfg: Config) !Db {
         return switch (cfg) {
             .postgres => |postgres_cfg| Db{
+                .underlying = .{
                     .postgres = try postgres.Db.open(postgres_cfg.conn_str),
                 },
+            },
             .sqlite => |lite_cfg| Db{
+                .underlying = .{
                     .sqlite = try sqlite.Db.open(lite_cfg.file_path),
                 },
+            },
         };
     }
+
     pub fn close(self: Db) void {
-        switch (self) {
+        switch (self.underlying) {
             .postgres => |pg| pg.close(),
             .sqlite => |lite| lite.close(),
         }
     }
 
-    pub fn exec(self: Db, sql: [:0]const u8, args: anytype, alloc: Allocator) !Results {
-        return switch (self) {
-            .postgres => |pg| Results{ .postgres = try pg.exec(sql, args, alloc) },
-            .sqlite => |lite| Results{ .sqlite = try lite.exec(sql, args) },
-        };
+    pub fn query(
+        self: Db,
+        comptime result_types: []const type,
+        sql: [:0]const u8,
+        args: anytype,
+        alloc: ?Allocator,
+    ) !Results(result_types) {
+        // Create fake transaction to use its functions
+        return (Tx{ .underlying = self.underlying }).query(result_types, sql, args, alloc);
+    }
+
+    pub fn exec(
+        self: Db,
+        sql: [:0]const u8,
+        args: anytype,
+        alloc: ?Allocator,
+    ) !void {
+        // Create fake transaction to use its functions
+        return (Tx{ .underlying = self.underlying }).exec(sql, args, alloc);
+    }
+
+    pub fn queryRow(
+        self: Db,
+        comptime result_types: []const type,
+        sql: [:0]const u8,
+        args: anytype,
+        alloc: ?Allocator,
+    ) !?Results(result_types).RowTuple {
+        // Create fake transaction to use its functions
+        return (Tx{ .underlying = self.underlying }).exec(sql, args, alloc);
+    }
+
+    pub fn insert(
+        self: Db,
+        comptime table: []const u8,
+        value: anytype,
+    ) !void {
+        // Create fake transaction to use its functions
+        return (Tx{ .underlying = self.underlying }).insert(table, value);
+    }
+
+    // Begins a transaction
+    pub fn begin(self: Db) !Tx {
+        const tx = Tx{ .underlying = self.underlying };
+        try tx.exec("BEGIN", .{}, null);
+
+        return tx;
     }
 };
+
+pub const Tx = struct {
+    underlying: DbUnion,
+
+    // internal helper fn
+    fn queryInternal(
+        self: Tx,
+        sql: [:0]const u8,
+        args: anytype,
+        alloc: ?Allocator,
+    ) !RawResults {
+        return switch (self.underlying) {
+            .postgres => |pg| RawResults{ .postgres = try pg.exec(sql, args, alloc) },
+            .sqlite => |lite| RawResults{ .sqlite = try lite.exec(sql, args) },
+        };
+    }
+
+    // Executes a query and returns the result set
+    pub fn query(
+        self: Tx,
+        comptime result_types: []const type,
+        sql: [:0]const u8,
+        args: anytype,
+        alloc: ?Allocator,
+    ) !Results(result_types) {
+        return Results(result_types){ .unerlying = try self.queryInternal(sql, args, alloc) };
+    }
+
+    // Executes a query without returning results
+    pub fn exec(
+        self: Tx,
+        sql: [:0]const u8,
+        args: anytype,
+        alloc: ?Allocator,
+    ) !void {
+        (try self.queryInternal(sql, args, alloc)).finish();
+    }
+
+    // Runs a query and returns a single row
+    pub fn queryRow(
+        self: Tx,
+        comptime result_types: []const type,
+        q: [:0]const u8,
+        args: anytype,
+        alloc: ?Allocator,
+    ) !?Results(result_types).RowTuple {
+        var results = try self.query(result_types, q, args, alloc);
+        defer results.finish();
+
+        const row = (try results.row(alloc)) orelse return null;
+        errdefer util.deepFree(alloc, row);
+
+        var more_rows = false;
+        while (try results.row(alloc)) |r| {
+            util.deepFree(alloc, r);
+            more_rows = true;
+        }
+        if (more_rows) return error.TooManyRows;
+
+        return row;
+    }
+
+    // Inserts a single value into a table
+    pub fn insert(
+        self: Tx,
+        comptime table: []const u8,
+        value: anytype,
+    ) !void {
+        const ValueType = comptime @TypeOf(value);
+        const table_spec = comptime table ++ build_field_list(ValueType, null);
+        const value_spec = comptime build_field_list(ValueType, "?");
+        const q = comptime std.fmt.comptimePrint(
+            "INSERT INTO {s} VALUES {s}",
+            .{ table_spec, value_spec },
+        );
+        try self.exec(q, value, null);
+    }
+
+    pub fn rollback(self: Tx) void {
+        self.exec("ROLLBACK", .{}, null) catch |err| {
+            std.log.err("Error occured during rollback operation: {}", .{err});
+        };
+    }
+
+    pub fn commit(self: Tx) !void {
+        try self.exec("COMMIT", .{}, null);
+    }
+};
+
+fn build_field_list(comptime T: type, comptime placeholder: ?[]const u8) []const u8 {
+    comptime {
+        const joiner = ",";
+        var result: []const u8 = "";
+        inline for (std.meta.fields(T)) |f| {
+            result = result ++ joiner ++ (placeholder orelse f.name);
+        }
+
+        return "(" ++ result[joiner.len..] ++ ")";
+    }
+}

src/sql/postgres.zig

@@ -84,14 +84,18 @@ pub const Db = struct {
 
     const format_text = 0;
     const format_binary = 1;
-    pub fn exec(self: Db, sql: [:0]const u8, args: anytype, alloc: Allocator) !Results {
+    pub fn exec(self: Db, sql: [:0]const u8, args: anytype, alloc: ?Allocator) !Results {
         const result = blk: {
-            var arena = std.heap.ArenaAllocator.init(alloc);
+            if (comptime args.len > 0) {
+                var arena = std.heap.ArenaAllocator.init(alloc orelse return error.AllocatorRequired);
                 defer arena.deinit();
                 const params = try arena.allocator().alloc(?[*]const u8, args.len);
                 inline for (args) |a, i| params[i] = if (try common.prepareParamText(arena, a)) |slice| slice.ptr else null;
 
                 break :blk c.PQexecParams(self.conn, sql.ptr, @intCast(c_int, params.len), null, params.ptr, null, null, format_text);
+            } else {
+                break :blk c.PQexecParams(self.conn, sql.ptr, 0, null, null, null, null, format_text);
+            }
         } orelse {
             std.log.err("Error occurred in sql query: {?s}", .{c.PQerrorMessage(self.conn)});
             return error.UnknownError;

src/sql/sqlite.zig

@@ -105,8 +105,10 @@ pub const Db = struct {
 
     pub fn exec(self: Db, sql: []const u8, args: anytype) !Results {
         var stmt: ?*c.sqlite3_stmt = undefined;
-        const err = c.sqlite3_prepare_v2(self.db, sql.ptr, @intCast(c_int, sql.len), &stmt, null);
-        if (err != c.SQLITE_OK) return handleUnexpectedError(self.db, err, sql);
+        switch (c.sqlite3_prepare_v2(self.db, sql.ptr, @intCast(c_int, sql.len), &stmt, null)) {
+            c.SQLITE_OK => {},
+            else => |err| return handleUnexpectedError(self.db, err, sql),
+        }
         errdefer switch (c.sqlite3_finalize(stmt)) {
             c.SQLITE_OK => {},
             else => |err| {

src/util/lib.zig

@@ -12,14 +12,14 @@ pub fn cloneStr(str: []const u8, alloc: std.mem.Allocator) ![]const u8 {
     return new;
 }
 
-pub fn deepFree(alloc: std.mem.Allocator, val: anytype) void {
+pub fn deepFree(alloc: ?std.mem.Allocator, val: anytype) void {
     const T = @TypeOf(val);
     switch (@typeInfo(T)) {
         .Pointer => |ptr| switch (ptr.size) {
-            .One => alloc.destroy(val),
+            .One => alloc.?.destroy(val),
             .Slice => {
                 for (val) |v| deepFree(alloc, v);
-                alloc.free(val);
+                alloc.?.free(val);
             },
             else => @compileError("Many and C-style pointers not supported by deepfree"),
         },