Support for `NOWAIT` / `SKIP LOCKED` options in locking clause

Issue type:

[x] feature request

Database system/driver:

[x] mssql [x] mysql / mariadb [x] oracle [x] postgres

TypeORM version:

[x] latest

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PostgreSQL, MySQL, MSSQL and Oracle (I think), and perhaps others, support NOWAIT and SKIP LOCKED options for row locking. The PostgreSQL documentation has a good explanation of these options, but in summary:

nowait

With the NOWAIT option, the statement reports an error if it is unable to take the lock.

SELECT * FROM jobs WHERE id = 5 FOR UPDATE NOWAIT

skip locked

With the SKIP LOCKED option, any selected rows that cannot be immediately locked are skipped.

SELECT * FROM jobs WHERE id = 5 FOR UPDATE SKIP LOCKED

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Currently, TypeORM only supports the bare FOR UPDATE clause, via the pessimistic_write lock mode.

Some additional considerations:

• These options are, in some databases, relatively new. SKIP LOCKED appeared in PostgreSQL 9.5 (2016). I think support in MySQL is even more recent. I’m not sure what TypeORM’s philosophy is on supporting newer SQL features?
• NOWAIT, by design, returns an error if the row is locked, so it seems necessary that an implementation of this option would have to handle this gracefully (a new Error type?)

[pleerock]

To not confuse things I would go this way:

1. deprecate setLock
2. create lockMode() method that will do same as setLock right now, e.g. rename setLock method
3. create lock() method that accepts string and do what you proposed

What do you think?

[clarkdave]

@pleerock These lock options aren’t specific to FOR UPDATE - they can be used with any “lock strength”, and also combined with an OF table_name to limit the lock to a specific table when multiple are involved.

For example, all of the following queries are valid:

SELECT * FROM table WHERE id = 1 FOR UPDATE;
SELECT * FROM table WHERE id = 1 FOR SHARE SKIP LOCKED;
SELECT * FROM table WHERE id = 1 FOR UPDATE NOWAIT;
SELECT * FROM table WHERE id = 1 FOR KEY SHARE SKIP LOCKED;

SELECT a.*, b.*
  FROM a
  LEFT JOIN b ON b.id = a.b_id
  FOR UPDATE OF a
  SKIP LOCKED;

With that in mind, could TypeORM support a more generic way to set the locking clause for a query? As an example from the wild, ActiveRecord lets you pass through an arbitrary string:

User
  .lock('FOR UPDATE OF users SKIP LOCKED')
  .where(:id => 1)
  .first

Maybe this could be supported in TypeORM by adding another override to setLock which accepts a raw string to use as the locking clause, as with other methods like addGroupBy:

const user = await connection
  .getRepository(User)
  .createQueryBuilder('user')
  .leftJoinAndSelect('user.photos', 'photo')
  .where({ id: 1 })
  .setLock('FOR UPDATE OF user SKIP LOCKED')
  // .setLock('FOR KEY SHARE OF user')
  // .setLock('FOR NO KEY UPDATE NOWAIT')
  // .setLock('FOR SHARE OF user')
  .getOne()

Thoughts?