Firestore无排序查询用Offset分页是否可行？需指定排序规则吗？

Great question—let’s break this down clearly:

Short answer: You should always specify an explicit sort order if you want reliable, predictable pagination.

Here’s the why behind that:

• No guaranteed implicit order in SQL
  The SQL standard doesn’t mandate that databases return rows in any fixed order unless you include an ORDER BY clause. While you might notice some databases returning rows in primary key order or insertion order by default, that’s just an implementation quirk—not a rule. Things like index changes, table updates, or even the database choosing a different execution plan can completely shuffle the result order between query runs.

• Unspecified sorting breaks pagination
  Without a consistent sort order, your OFFSET and LIMIT will behave unpredictably. Imagine you’re paginating through 100 rows: first you run SELECT * FROM my_table LIMIT 10 OFFSET 0 and get a set of rows. Then you run SELECT * FROM my_table LIMIT 10 OFFSET 10—but if the row order changed, you might end up with duplicate rows from the first page, or miss some rows entirely. There’s no way to ensure you’re stepping through the dataset correctly.

• Don’t rely on "hidden" sorting like key order
  Even if your database seems to default to primary key sorting, don’t count on it. Database vendors can adjust this behavior in updates, and edge cases (like concurrent writes, partitioned tables, or index rebuilds) can disrupt that implicit order. The only safe way to keep pagination consistent is to define an explicit ORDER BY—preferably using a unique column (like a primary key) to avoid situations where multiple rows have the same sort value (which could also cause order shifts).

Example of reliable pagination: #

SELECT * FROM customers
ORDER BY customer_id ASC -- Unique primary key ensures consistent ordering
LIMIT 15 OFFSET 30;

If you don’t have a single unique column, combine columns to create a unique sort key:

SELECT * FROM transactions
ORDER BY transaction_date DESC, transaction_id ASC
LIMIT 10 OFFSET 20;

内容的提问来源于stack exchange，提问作者MiguelSlv