Memory leak/overload when looping by index over a large query and updating each DB record

I am importing a CSV file into a temporary table and then running a select query that joins my actual database table with the temporary table, looking for any changes in the data. If changes exist, the select query is looped from 1 to #recordCount# and an update is applied to each record via cfquery. It runs very quickly (much more quickly than looping the query itself), but my memory spikes and overloads after about 1500 updates are completed. I need to be able to do upwards of 20000 at a time, without killing my system. I have tried manually setting the runtime garbage collection to trigger after X number of loops, but that doesn't seem to help. I am running CF8. See below for loop example:

<cfloop from="1" to="#updatedRecordsQuery.recordCount#" index="a">

<cftry>

                <cfquery datasource="#db#" name="doUpdate">

                    UPDATE

                        CI

                    SET

                        firstname = <cfqueryparam cfsqltype="cf_sql_varchar" value="#updatedRecordsQuery.firstname[a]#" />,

                        lastname = <cfqueryparam cfsqltype="cf_sql_varchar" value="#updatedRecordsQuery.lastname[a]#" />,

                        etc, for about 15 various fields

                    FROM

                        client_info CI

                    WHERE

                        CI.client_id = <cfqueryparam cfsqltype="cf_sql_integer" value="#updatedRecordsQuery.client_id[a]#" />

                </cfquery>

                <cfcatch type="database">

                    <cfset local.updateErrorList = listappend(local.updateErrorList,updatedRecordsQuery.client_id[a]) />

                    <cfset local.error = true />

                </cfcatch>

           </cftry>

</cfloop>