README

Batch imports are a common task for any larger system. This packages implements a batch import for laravel's eloquent models.

How to use

First the ProvidesBatchImport and the DbExtensions (from package mehr-it/lara-db-ext) trait must be added to a model:

class User extends Model {
    uses DbExtensions;
    uses ProvidesBatchImport;
}

This adds a new static method called batchImport() to the model. It creates a new batch import instance which can be configured and used to import data. See following example:

User::batchImport()
    ->matchBy('name')
    ->updateIfExists(['phone', 'email'])
    ->import([
        new User([
            'name' => 'Hans Maier',
            'phone' = '+ 49 6081 1234',
            'email' = 'hans.maier@example.com',
        ]),
        new User([
            'name' => 'Max Mustermann',
            'phone' = '+ 49 61200 1234',
            'email' = 'max.m@example.com',
        ]),
        /* ... */
    ]);

The example code intents to import user data. New records are insert for existing records (determined by matching "name" field) the "phone" and "email" fields are updated.

Behind the scenes, the import data is processed in chunks of 500 records: For each chunk, the database is searched for existing records. In the given example, the users table is queried for records with a name matching any of the given names within the current chunk. The result is compared to the chunk data: Existing records are checked for required updates and new records are marked to insert. The resulting modifications are sent to the database using bulk insert/update strategies.

Record matching conditions

The fields used to consider two records as "matching" (and therefore to update instead of insert new data) can be specified using the matchBy() method. Multiple fields can be passed as array.

Records are considered to match if the string representation of all given matchBy fields is equal. By default matching is case-sensitive. Set the second parameter to false, for case-insensitive matching.

Attention: The according to SQL's "three-valued logic" comparing null values never returns true. This means, that a record won't match any other record if any of the "matchBy" fields is null!

The comparison is limited to equal comparison, however a callable can be passed to process the value before comparison:

$import->matchBy(
    [
        'name' => function($v) { return substr($v, 0, 1); }
    ],
    false    /* false for case-insensitive */
);

Without any explicitly setting "matchBy" fields, the model's primary key is used.

Record matching internals

To match against existing records, the "matchBy" fields are converted to query conditions wherever possible. But callables cannot be used in SQL.

After existing records have been fetched using the "matchBy" conditions, a comparison key using all "matchBy" criteria is build for each record. Here any callables passed to "matchBy" are invoked. At this point also case-insensitive matching normalizes all keys to lower case. Models with the same comparison key are treated as "equal".

If you need to adapt the comparison key for models, a custom callback for generating comparison keys can be set using withComparisonKey().

Modify model query

Sometimes you might want to modify the model query. Imagine you are using soft deletes and want trashed models to be included. Use the tapModelQuery() method for such case:

$import->tapModelQuery(function($query){
    return $query->withTrashed();
});

// when modifying the model query, usage of bypassModel() is mandatory
$import->bypassModel();

Import The model query can only be modified when bypassModel() is used!

Updating existing records

If existing records should be updated, the updateIfExists() method can be used to specify a list of fields to update in case of existence.

If updateIfExists is not invoked, only new records are insert!

The updateIfExists() method also accepts updates with a static value, an SQL expression or a callable to generate a more customized value:

$import->updateIfExists([
    'phone' => function($v) {
        return str_replace(' ', '', $v);       
    },
    'email' => new Expression('lower(email)'),
]);

Adding callbacks

Often it is required to know which records have been affected by the batch import. The onInserted(), onUpdated() and onInsertedOrUpdated() methods can be used to register callbacks to receive the corresponding records (in chunks of 500 per default).

$import->onUpdated(function($records) {
    foreach($record as $currRecord) {
        /* do s.th. */
    }
});

Note: The model instances passed to the callbacks are not inevitably the same as the ones passed to the import function. Further they do not contain updated timestamps or inserted id values, because mass insert/update strategies are used for database operations.

Determining missing records

Determining which records have been updated or inserted is quite easy because all these records are "seen" by the bulk import algorithm. But the bulk import is unaware of any other records.

Nevertheless, it can help to detect them afterwards. It can mark any "seen" records with a sequential batch id. This makes it possible to query for "missing" records in a second step. There a new batch id must be passed to the withBatchId() method:

$import->withBatchId(100001);

This will set the "last_batch_id" (which must exist in the database) to the given value.

It is important to increment the batch id for each new batch import!

After the import, any missing records can be queried using the whereMissingAfterBatch() condition:

User::query()
    ->whereMissingAfterBatch(100001)
    ->chunk(500, function($records) {
        /* process missing records */
    });

It returns any records where the batch id is null or less than the given value.

For performant SQL operations, corresponding indices should be set for the tables.

Models with batch id

Following best practices, the batch id should be generated per model. Therefor it is a good idea to add the generation logic to the model class. Implementing the GeneratesBatchIds interface lets batch import operations automatically fetch the next batch id from the model without manually invoking withBatchId():

class User extends Model implements GeneratesBatchIds {
    
    /**
     * Gets the next batch id
     * @return string The next batch id as string
     */
    public function nextBatchId(): string {
        
        /* custom logic here */
        
    }

}

The import() method accepts a second parameter which will return the last used batch id. Alternatively, the getLastBatchId() method can be used:

$import->import($data, $lastBatchId);

// or

$import->getLastBatchId();

Prepared imports

Sometimes it can be very handy to prepare an import, then collect the data and flush the import afterwards. The prepare() method can be used for this:

// prepare
$prepared = $import->prepare();

// add records
$prepared->add($record1);
$prepared->addMultiple([$record2, $record3]);

// flush
$prepared->flush($lastBatchId);

Bypassing models

Using models for managing database data offers a clean and comfortable interface. However, this comes with the drawback of some overhead. When performing bulk imports with large datasets model attribute set/get operations are performed a thousand times. The performance impact can be significant.

If you do not need model attribute functionality, such as mutators, accessors, casts and so on the bypassModel() method can make your application much faster.

$import->bypassModel();

In such case you must provide the data as raw arrays instead of model instances.

The bypassModel() method also accepts a second parameter called "rawComparators". It accepts custom comparator functions for fields. These are used to compare the new data with existing data to detect changes. Eg. a decimal stored in database might be returned as '12.90' but your input might be '12.9'. Without a custom comparator the row will be detected as change. But a custom comparator can avoid this:

$import->bypassModel(true, [
    'price' => function($new, $old) {
        return bccomp($new, $old, 2);
    }
]);

mehr-it / lara-db-batch-import

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