class Upsert

class Upsert extends QueryUpsert {
    
    /**
     * {@inheritdoc}
     */
    public function execute() {
        if (!$this->preExecute()) {
            return NULL;
        }
        $stmt = $this->connection
            ->prepareStatement((string) $this, $this->queryOptions, TRUE);
        // Fetch the list of blobs and sequences used on that table.
        $table_information = $this->connection
            ->schema()
            ->queryTableInformation($this->table);
        $max_placeholder = 0;
        $blobs = [];
        $blob_count = 0;
        foreach ($this->insertValues as $insert_values) {
            foreach ($this->insertFields as $idx => $field) {
                if (isset($table_information->blob_fields[$field]) && $insert_values[$idx] !== NULL) {
                    $blobs[$blob_count] = fopen('php://memory', 'a');
                    fwrite($blobs[$blob_count], $insert_values[$idx]);
                    rewind($blobs[$blob_count]);
                    $stmt->getClientStatement()
                        ->bindParam(':db_insert_placeholder_' . $max_placeholder++, $blobs[$blob_count], \PDO::PARAM_LOB);
                    // Pre-increment is faster in PHP than increment.
                    ++$blob_count;
                }
                else {
                    $stmt->getClientStatement()
                        ->bindParam(':db_insert_placeholder_' . $max_placeholder++, $insert_values[$idx]);
                }
            }
            // Check if values for a serial field has been passed.
            if (!empty($table_information->serial_fields)) {
                foreach ($table_information->serial_fields as $index => $serial_field) {
                    $serial_key = array_search($serial_field, $this->insertFields);
                    if ($serial_key !== FALSE) {
                        $serial_value = $insert_values[$serial_key];
                        // Sequences must be greater than or equal to 1.
                        if ($serial_value === NULL || !$serial_value) {
                            $serial_value = 1;
                        }
                        // Set the sequence to the bigger value of either the passed
                        // value or the max value of the column. It can happen that another
                        // thread calls nextval() which could lead to a serial number being
                        // used twice. However, trying to insert a value into a serial
                        // column should only be done in very rare cases and is not thread
                        // safe by definition.
                        $this->connection
                            ->query("SELECT setval('" . $table_information->sequences[$index] . "', GREATEST(MAX(" . $serial_field . "), :serial_value)) FROM {" . $this->table . "}", [
                            ':serial_value' => (int) $serial_value,
                        ]);
                    }
                }
            }
        }
        $options = $this->queryOptions;
        if (!empty($table_information->sequences)) {
            $options['sequence_name'] = $table_information->sequences[0];
        }
        // Re-initialize the values array so that we can re-use this query.
        $this->insertValues = [];
        // Create a savepoint so we can rollback a failed query. This is so we can
        // mimic MySQL and SQLite transactions which don't fail if a single query
        // fails. This is important for tables that are created on demand. For
        // example, \Drupal\Core\Cache\DatabaseBackend.
        $this->connection
            ->addSavepoint();
        try {
            $stmt->execute(NULL, $options);
            $this->connection
                ->releaseSavepoint();
            return $stmt->rowCount();
        } catch (\Exception $e) {
            $this->connection
                ->rollbackSavepoint();
            $this->connection
                ->exceptionHandler()
                ->handleExecutionException($e, $stmt, [], $options);
        }
    }
    
    /**
     * {@inheritdoc}
     */
    public function __toString() {
        // Create a sanitized comment string to prepend to the query.
        $comments = $this->connection
            ->makeComment($this->comments);
        // Default fields are always placed first for consistency.
        $insert_fields = array_merge($this->defaultFields, $this->insertFields);
        $insert_fields = array_map(function ($field) {
            return $this->connection
                ->escapeField($field);
        }, $insert_fields);
        $query = $comments . 'INSERT INTO {' . $this->table . '} (' . implode(', ', $insert_fields) . ') VALUES ';
        $values = $this->getInsertPlaceholderFragment($this->insertValues, $this->defaultFields);
        $query .= implode(', ', $values);
        // Updating the unique / primary key is not necessary.
        unset($insert_fields[$this->key]);
        $update = [];
        foreach ($insert_fields as $field) {
            // The "excluded." prefix causes the field to refer to the value for field
            // that would have been inserted had there been no conflict.
            $update[] = "{$field} = EXCLUDED.{$field}";
        }
        $query .= ' ON CONFLICT (' . $this->connection
            ->escapeField($this->key) . ') DO UPDATE SET ' . implode(', ', $update);
        return $query;
    }

}