Add query builder struct

This commit is contained in:
jaina heartles 2022-08-07 00:54:22 -07:00
parent ee4aa9e826
commit b6a3b68cff

View file

@ -16,7 +16,7 @@ fn baseTypeName(comptime T: type) []const u8 {
}
fn tableName(comptime T: type) String {
return util.case.pascalToSnake(baseTypeName(T));
return comptime util.case.pascalToSnake(baseTypeName(T));
}
// Represents a table bound to an identifier in a sql query
@ -29,6 +29,20 @@ pub const QueryTable = struct {
const f = @as(std.meta.FieldEnum(self.Model), lit);
return comptimePrint("{s}.{s}", .{ self.as, @tagName(f) });
}
pub fn select(comptime self: QueryTable, comptime lit: @Type(.EnumLiteral)) ResultColumn {
return .{
.@"type" = std.meta.fieldInfo(self.Model, lit).field_type,
.field = self.field(lit),
};
}
// returns the declaration to put in the FROM clause
fn declarationStr(comptime self: QueryTable) String {
comptime {
return comptimePrint("{s} AS {s}", .{ tableName(self.Model), self.as });
}
}
};
fn makeQueryTable(comptime Model: type, comptime table_index: usize) QueryTable {
@ -51,6 +65,16 @@ test "QueryTable.field" {
try std.testing.expectEqualStrings("my_type.id", tbl.field(.id));
}
test "QueryTable.declarationStr" {
const MyTable = struct { id: i64 };
const tbl = QueryTable{
.Model = MyTable,
.as = "some_table",
};
try std.testing.expectEqualStrings("my_table AS some_table", tbl.declarationStr());
}
test "queryTables constructor" {
const MyTable = struct { id: i64 };
const MyOtherTable = struct { val: i64 };
@ -63,9 +87,14 @@ test "queryTables constructor" {
try std.testing.expectEqualStrings("my_other_table_1", qt[1].as);
}
fn map(comptime T: type, comptime R: type, comptime vals: []const T, comptime func: fn (T, usize) R) *const [vals.len]R {
fn map(comptime T: type, comptime R: type, comptime vals: []const T, comptime func: anytype) *const [vals.len]R {
var result: [vals.len]R = undefined;
for (vals) |v, i| result[i] = func(v, i);
if (@typeInfo(@TypeOf(func)).Fn.args.len == 2) {
for (vals) |v, i| result[i] = @as(R, func(v, i));
} else {
for (vals) |v, i| result[i] = @as(R, func(v));
}
return &result;
}
@ -134,3 +163,70 @@ test "Condition.str()" {
} }).str(),
);
}
const ResultColumn = struct {
@"type": type,
field: []const u8,
pub fn toSelectClause(comptime self: ResultColumn) String {
return self.field;
}
pub fn toStructField(comptime self: ResultColumn) std.builtin.Type.StructField {
return .{
.name = self.field,
.field_type = self.@"type",
.default_value = null,
.is_comptime = false,
.alignment = 0,
};
}
};
// Represents a full SQL query
pub const Query = struct {
tables: []const QueryTable,
fields: []const ResultColumn,
filter: Condition,
pub fn str(comptime self: Query) String {
const table_aliases = map(QueryTable, String, self.tables, QueryTable.declarationStr);
const select_clauses = map(ResultColumn, String, self.fields, ResultColumn.toSelectClause);
return comptimePrint("SELECT {s} FROM {s} WHERE {s}", .{ join(select_clauses, ", "), join(table_aliases, ", "), self.filter.str() });
}
pub fn rowType(comptime self: Query) type {
const struct_fields = map(ResultColumn, std.builtin.Type.StructField, self.fields, ResultColumn.toStructField);
return @Type(.{ .Struct = .{
.layout = .Auto,
.fields = struct_fields,
.decls = &.{},
.is_tuple = true,
} });
}
};
test "Query" {
const MyTable = struct { id: i64 };
const MyOtherTable = struct {
val: []const u8,
};
const qt = queryTables(&.{ MyTable, MyOtherTable, MyTable });
const q = comptime Query{
.tables = qt,
.fields = &.{ qt[0].select(.id), qt[1].select(.val) },
.filter = Condition{ .eql = .{ .lhs = qt[0].field(.id), .rhs = qt[2].field(.id) } },
};
try std.testing.expectEqualStrings(
"SELECT my_table_0.id, my_other_table_1.val " ++
"FROM my_table AS my_table_0, my_other_table AS my_other_table_1, my_table AS my_table_2 " ++
"WHERE (my_table_0.id = my_table_2.id)",
comptime q.str(),
);
const fields = std.meta.fields(q.rowType());
try std.testing.expectEqual(i64, fields[0].field_type);
try std.testing.expectEqual([]const u8, fields[1].field_type);
}