Saved search function to fetch the primary contact from the transaction record.

/**
         * Function to get the primary contact 
         * @param {*} salesOrderId sales order id
         * @param {*} recType record type
         * @returns transaction details
         */
        function getPrimaryContact(salesOrderId, recType) {
            try {
                let primaryContactName;
                let estimateSearchObj = search.create({
                    type: "transaction",
                    filters:
                        [
                            ["type", "anyof", recType],
                            "AND",
                            ["mainline", "is", "T"],
                            "AND",
                            ["internalid", "anyof", salesOrderId]
                        ],
                    columns:
                        [
                            search.createColumn({ name: "internalid", label: "Internal ID" }),
                            search.createColumn({
                                name: "entityid",
                                join: "contactPrimary",
                                label: "Name"
                            })
                        ]
                });
                var searchResultCount = estimateSearchObj.runPaged().count;
                log.debug("estimateSearchObj result count", searchResultCount);
                estimateSearchObj.run().each(function (result) {
                    // .run().each has a limit of 4,000 results
                    primaryContactName = result.getValue({
                        name: "entityid",
                        join: "contactPrimary",
                        label: "Name"
                    });
                });
                log.debug('primaryContactName', primaryContactName);
                return primaryContactName;

            } catch (e) {
                log.error('error @ getPrimaryContact', e);
                return '';
            }
        }