Question

我的代码基于@ zzzeeek对this question 的回答。我将它扩展了一点，因此它考虑了Postgresql的NULL和ARRAY。

class values(FromClause):
    named_with_column = True

    def __init__(self, columns, *args, **kw):
        self._column_args = columns
        self.list = args
        self.alias_name = self.name = kw.pop('alias_name', None)

    def _populate_column_collection(self):
        # self._columns.update((col.name, col) for col in self._column_args)
        for c in self._column_args:
        c._make_proxy(self, c.name)


@compiles(values)
def compile_values(element, compiler, asfrom=False, **kw):
    columns = element.columns
    v = "VALUES %s" % ", ".join(
    "(%s)" % ", ".join(
        ((compiler.visit_array(elem)+'::'+str(column.type)) if isinstance(column.type, ARRAY) else
         compiler.render_literal_value(elem, column.type))
        if elem is not None else compiler.render_literal_value(elem, NULLTYPE)
        for elem, column in zip(tup, columns))
    for tup in element.list
    )
    if asfrom:
        if element.alias_name:
            v = "(%s) AS %s (%s)" % (v, element.alias_name, (", ".join(c.name for c in element.columns)))
        else:
            v = "(%s)" % v
    return v

一切正常，直到事实证明我无法使用＆＃34;％＆＃34; -sign插入这个VALUES子句 - 它们在结果语句中被内联，这似乎导致绑定问题< / p>

我想如果我们使用render_literal_value()代替bindparam()，我们可以避免这样的错误。但是@compiles下的所有内容都应该返回纯文本，我是对的吗？我如何修改它以获得基于参数的查询？

Answer 1

我明白了。 bindparams的实际值保存在名为SQLCompiler的对象中，该对象通常是特定于方言的。 Here(link to GitHub)是在查询编译过程中将bindparams存储在SQLCompiler实例中的地方

因此，我的代码段的最终版本如下所示：

class values(FromClause):
    named_with_column = True

    def __init__(self, columns, *args, **kw):
        self._column_args = columns
        self.list = args
        self.alias_name = self.name = kw.pop('alias_name', None)

    def _populate_column_collection(self):
        # self._columns.update((col.name, col) for col in self._column_args)
        for c in self._column_args:
            c._make_proxy(self, c.name)


@compiles(values)
def compile_values(clause, compiler, asfrom=False, **kw):
    def decide(value, column):
        add_type_hint = False
        if isinstance(value, array) and not value.clauses:  # for empty array literals
            add_type_hint = True

        if isinstance(value, ClauseElement):
            intermediate = compiler.process(value)
            if add_type_hint:
                intermediate += '::' + str(column.type)
            return intermediate

        elif value is None:
            return compiler.render_literal_value(
                value,
                NULLTYPE
            ) + '::' + str(column.type)
        else:
            return compiler.process(
                bindparam(
                    None,
                    value=compiler.render_literal_value(
                        value,
                        column.type
                    ).strip("'")
                )
            ) + '::' + str(column.type)

    columns = clause.columns
    v = "VALUES %s" % ", ".join(
        "(%s)" % ", ".join(
            decide(elem, column)
            for elem, column in zip(tup, columns))
        for tup in clause.list
    )
    if asfrom:
        if clause.alias_name:
            v = "(%s) AS %s (%s)" % (v, clause.alias_name, (", ".join(c.name for c in clause.columns)))
        else:
            v = "(%s)" % v
    return v

如何在自定义编译表达式中使用bindparam（）？

1 个答案: