[10.x] Ensuring Primary Reference on Retry in createOrFirst()

[mpyw]

Summary

This PR refines the createOrFirst() method to guarantee referencing the primary database when re-attempting record retrieval after a UniqueConstraintViolationException.

Details:

• [10.x] Adds a createOrFirst method to Eloquent #47973
  • [10.x] Fix createOrFirst on transactions #48144

The existing createOrFirst() method, when facing a unique constraint violation, retries by fetching the matching record. However, in environments with replication, there's no assurance that the newly created record is immediately available on replicas due to possible replication lags.

To address this:

public function createOrFirst(array $attributes = [], array $values = [])
{
    try {
        return $this->getQuery()->withSavepointIfNeeded(fn () => $this->create(array_merge($attributes, $values)));
    } catch (UniqueConstraintViolationException $exception) {
        return $this->useWritePdo()->where($attributes)->first();
    }
}

With this change, in case of a retry, the method explicitly references the primary database using useWritePdo(), ensuring immediate and accurate record retrieval without being affected by replication delays.

[mpyw]

We need to fix unit tests with Mockery. Okay

[taylorotwell]

Why did you only update one of the createOrFirst methods?

[mpyw]

Oops, sorry. I've just noticed that there are more createOrFirst methods. I'll check it out, thanks

[tonysm]

@mpyw doesn't Eloquent automatically switches to the write connection after a write attempt (INSERT, UPDATE, or DELETE)? I thought about that in the original PR but I thought it was the case.

The docs say that the sticky option can be used to control that and the example for using read/write replicas has it set to true, so I assumed that was the "default" behavior:

The sticky option is an optional value that can be used to allow the immediate reading of records that have been written to the database during the current request cycle. If the sticky option is enabled and a "write" operation has been performed against the database during the current request cycle, any further "read" operations will use the "write" connection. This ensures that any data written during the request cycle can be immediately read back from the database during that same request. It is up to you to decide if this is the desired behavior for your application.

[mpyw]

@tonysm I am aware of this feature, but I believe the read connection actually switches to the primary only after a successful write attempt.

framework/src/Illuminate/Database/Connection.php

Lines 560 to 613 in 3365194

	/**
	* Execute an SQL statement and return the boolean result.
	*
	* @param string $query
	* @param array $bindings
	* @return bool
	*/
	public function statement($query, $bindings = [])
	{
	return $this->run($query, $bindings, function ($query, $bindings) {
	if ($this->pretending()) {
	return true;
	}
	$statement = $this->getPdo()->prepare($query);
	$this->bindValues($statement, $this->prepareBindings($bindings));
	$this->recordsHaveBeenModified();
	return $statement->execute();
	});
	}
	/**
	* Run an SQL statement and get the number of rows affected.
	*
	* @param string $query
	* @param array $bindings
	* @return int
	*/
	public function affectingStatement($query, $bindings = [])
	{
	return $this->run($query, $bindings, function ($query, $bindings) {
	if ($this->pretending()) {
	return 0;
	}
	// For update or delete statements, we want to get the number of rows affected
	// by the statement and return that back to the developer. We'll first need
	// to execute the statement and then we'll use PDO to fetch the affected.
	$statement = $this->getPdo()->prepare($query);
	$this->bindValues($statement, $this->prepareBindings($bindings));
	$statement->execute();
	$this->recordsHaveBeenModified(
	($count = $statement->rowCount()) > 0
	);
	return $count;
	});
	}

According to this, statement pre-emptively calls recordsHaveBeenModified, whereas the actual affectingStatement used by create calls it post-execution. This indicates that recordsHaveBeenModified is not called when an exception is thrown in execute. Therefore, after catching an exception and correcting the primary reference, this mechanism does not work, and we need to explicitly apply useWritePdo in our code.