Knex postgres upsert

upsert.js

    /**
     * Perform an "Upsert" using the "INSERT ... ON CONFLICT ... " syntax in PostgreSQL 9.5
     * @link http://www.postgresql.org/docs/9.5/static/sql-insert.html
     * @author https://github.com/adnanoner
     * inspired by: https://gist.github.com/plurch/118721c2216f77640232
     * @param {string} tableName - The name of the database table
     * @param {string} conflictTarget - The column in the table which has a unique index constraint
     * @param {Object} itemData - a hash of properties to be inserted/updated into the row
     * @returns {Promise} - A Promise which resolves to the inserted/updated row
     */
    const upsert = (tableName, itemData, conflictTarget) => {
        let itemsArray = [];
        if (Array.isArray(itemData)) {
            itemsArray = itemData;
        } else {
            itemsArray[0] = itemData;
        }
        const itemKeys = Object.keys(itemsArray[0]);

        const exclusions = itemKeys
           .filter(c => c !== conflictTarget)
           .map(c => bookshelf.knex.raw('?? = EXCLUDED.??', [c, c]).toString())
           .join(',\n');

        let valuesPreparedString = '';
        let preparedValues = [];
        itemsArray.forEach((item) => {
            valuesPreparedString += '(';
            for (let i = 0; i < itemKeys.length - 1; i += 1) {
                valuesPreparedString += '?, ';
            }
            valuesPreparedString += '?), ';
            preparedValues = preparedValues.concat(Object.values(item));
        });
        // Remove last trailing comma
        valuesPreparedString = valuesPreparedString.replace(/,\s*$/, '');

        // if we have an array of conflicting targets to ignore process it
        let conflict = '';
        if (conflictTarget) {
            conflict += '(';
            if (Array.isArray(conflictTarget)) {
                for (let i = 0; i < conflictTarget.length - 1; i += 1) {
                    conflict += '??, ';
                }
                preparedValues = preparedValues.concat(conflictTarget);
            } else {
                preparedValues.push(conflictTarget);
            }
            conflict += '??)';
        }

        const itemKeysPlaceholders = itemKeys.map(() => '??').join(',');

        return bookshelf.knex.raw(`
            INSERT INTO ?? (${itemKeysPlaceholders})
            VALUES ${valuesPreparedString}
            ON CONFLICT ${conflict} DO UPDATE SET
            ${exclusions}
            RETURNING *;
            `.trim(),
            [tableName, ...itemKeys, ...preparedValues])
            .then(result => result.rows);        
    };

@Whoaa512 I think you might have to change the itemsKeysPlaceholders to ?? instead of ?

Positional bindings ? are interpreted as values and ?? are interpreted as identifiers.