class Upsert

abstract class Upsert extends Query implements \Countable {
    use InsertTrait;
    
    /**
     * The unique or primary key of the table.
     *
     * @var string
     */
    protected $key;
    
    /**
     * Constructs an Upsert object.
     *
     * @param \Drupal\Core\Database\Connection $connection
     *   A Connection object.
     * @param string $table
     *   Name of the table to associate with this query.
     * @param array $options
     *   (optional) An array of database options.
     */
    public function __construct(Connection $connection, $table, array $options = []) {
        // @todo Remove $options['return'] in Drupal 11.
        // @see https://www.drupal.org/project/drupal/issues/3256524
        $options['return'] = Database::RETURN_AFFECTED;
        parent::__construct($connection, $options);
        $this->table = $table;
    }
    
    /**
     * Sets the unique / primary key field to be used as condition for this query.
     *
     * @param string $field
     *   The name of the field to set.
     *
     * @return $this
     */
    public function key($field) {
        $this->key = $field;
        return $this;
    }
    
    /**
     * Preprocesses and validates the query.
     *
     * @return bool
     *   TRUE if the validation was successful, FALSE otherwise.
     *
     * @throws \Drupal\Core\Database\Query\NoUniqueFieldException
     * @throws \Drupal\Core\Database\Query\FieldsOverlapException
     * @throws \Drupal\Core\Database\Query\NoFieldsException
     */
    protected function preExecute() {
        // Confirm that the user set the unique/primary key of the table.
        if (!$this->key) {
            throw new NoUniqueFieldException('There is no unique field specified.');
        }
        // Confirm that the user did not try to specify an identical
        // field and default field.
        if (array_intersect($this->insertFields, $this->defaultFields)) {
            throw new FieldsOverlapException('You may not specify the same field to have a value and a schema-default value.');
        }
        // Don't execute query without fields.
        if (count($this->insertFields) + count($this->defaultFields) == 0) {
            throw new NoFieldsException('There are no fields available to insert with.');
        }
        // If no values have been added, silently ignore this query. This can happen
        // if values are added conditionally, so we don't want to throw an
        // exception.
        return isset($this->insertValues[0]) || $this->insertFields;
    }
    
    /**
     * Executes the UPSERT operation.
     *
     * @return int
     *   An integer indicating the number of rows affected by the operation. Do
     *   not rely on this value as a precise indication of the actual rows
     *   affected: different database engines return different values.
     */
    public function execute() {
        if (!$this->preExecute()) {
            return NULL;
        }
        $max_placeholder = 0;
        $values = [];
        foreach ($this->insertValues as $insert_values) {
            foreach ($insert_values as $value) {
                $values[':db_insert_placeholder_' . $max_placeholder++] = $value;
            }
        }
        $stmt = $this->connection
            ->prepareStatement((string) $this, $this->queryOptions, TRUE);
        try {
            $stmt->execute($values, $this->queryOptions);
            $affected_rows = $stmt->rowCount();
        } catch (\Exception $e) {
            $this->connection
                ->exceptionHandler()
                ->handleExecutionException($e, $stmt, $values, $this->queryOptions);
        }
        // Re-initialize the values array so that we can re-use this query.
        $this->insertValues = [];
        return $affected_rows;
    }

}