How to create a paging function with MySQL and ColdFusion - mysql

Question

I'm trying to create pagination for search results using MySQL and ColdFusion. My intention is to only retrieve the queries that can be displayed on a single page, thus making the process efficient. I tried using two queries in my function, but I could not return two variables to the cfinvoke.
The following code does not paginate, but it displays the result search results using a CFC:
<!---DEFINE DEFAULT STATE--->
<cfparam name="variables.searchResponse" default="">
<cfparam name="URL.titleName" default="">
<cfparam name="URL.genreID" default="">
<cfparam name="URL.platformID" default="">
<!---TitleName can only be blank if one or both genre and platform are selected--->
<cfif StructKeyExists(URL, "searchQuery") AND (Len(Trim(URL.titleName)) LTE 2 AND Len(URL.genreID) IS 0 AND Len(URL.platformID) IS 0)>
<cfset variables.searchResponse = "invalidString">
<cfelseif StructKeyExists(URL, "searchQuery")>
<cfinvoke component="gz.cfcomp.test" method="searchGames" returnvariable="resultData" argumentcollection="#URL#">
<cfset variables.searchResponse = "hasResult">
</cfif>
<cfif searchResponse EQ "hasResult" AND resultData.RecordCount EQ 0>
<cfset variables.searchResponse = "noResult">
</cfif>
Using this logic, I can display what I need to display on the page:
<cfif searchResponse EQ "invalidString">
<cfoutput>Invalid search</cfoutput>
</cfif>
<cfif searchResponse EQ "noResult">
<cfoutput>No results found</cfoutput>
</cfif>
<cfif searchResponse EQ "hasResult">
<cfoutput>Display Results</cfoutput>
</cfif>
If I were executing the queries on the same page, it would be easy to follow the many tutorials out there. But the queries are executing in a function. Displaying the data is easy, but paginating it has become a nightmare for me. Here is my function:
<cffunction name="searchGames" access="public" output="false">
<cfargument name="titleName" required="no" type="string">
<cfargument name="genreID" required="no" type="string">
<cfargument name="platformID" required="no" type="string">
<!--- DEFINE LOCAL VARIABLES--->
<cfset var resultData = "">
<!---GET DATA--->
<cfquery name="resultData" datasource="myDSN">
SELECT *
<!---JOINS FOR GENRE/PLATFORM GO HERE--->
WHERE
<!---CONDITIONS GO HERE--->
</cfquery>
<!---RETURN VARIABLE--->
<cfreturn resultData>
</cffunction>
To paginate, I thought about modifying my function to the following (a new query using a count statement):
<!--- DEFINE LOCAL VARIABLES--->
<cfset var resultCount = "">
<!---GET DATA--->
<cfquery name="resultCount" datasource="myDSN">
SELECT COUNT(gameID) AS rowsFound FROM GAMES
<!---JOINS FOR GENRE/PLATFORM GO HERE--->
WHERE
<!---CONDITIONS GO HERE--->
</cfquery>
<!---RETURN VARIABLE--->
<cfreturn resultCount>
Then I figured if there is a result to return, I would execute a nested query and create the pagination variables:
<cfif resultCount.rowsFound GTE 0>
<cfparam name="pageNumber" default="1">
<cfset var recordsPerPage = 5>
<cfset var numberOfPages = Int(resultCount.RecordCount / recordsPerPage)>
<cfset var recordsToSkip = pageNumber * recordsPerPage - recordsPerPage>
<!---DEFINE LOCAL VARIABLE--->
<cfset var resultData = "">
<cfquery name="resultData" datasource="myDSN">
<!---GET DATA AND SEND IT BACK USING LIMIT WITH #recordsToSkip# and #RecordsPerPage#--->
</cfquery>
<!---RETURN VARIABLE--->
<cfreturn resultData>
</cffunction>
I figured I would return two variables: resultCount and resultData. I would use #resultCount# to build my pagination, and #resultData# to display the output. The problem is I can't return two variables in the same cfinvoke tag. Any ideas of how to approach the the right way? I'm totally lost as to the logic I need to follow.
EDIT: I'm using the following code to paginate now (the only problem is now I have to repass all the search filters back into the URL because using #CGI.SCRIPT_NAME# clears them):
<cfif searchResponse EQ "hasResult">
<!---BASICALLY, IF resultCount.rowsFound is not 0, execute this method--->
<cfinvoke component="gz.cfcomp.test" method="getResult" returnvariable="resultData" argumentcollection="#URL#">
<cfif URL.currentPage IS 1>
--
<cfelse>
Prev Page
</cfif>
<cfif URL.currentPage * recordsPerPage LT resultCount.rowsFound>
Next Page
<cfelse>
--
</cfif>
</cfif>

Answer 1

If your results is not huge, you can stay with the same SQL that returns everything and use
<cfoutput query="data" startrow="#url.start#" maxrows="#recordsPerPage#">
when you display it, see: http://www.coldfusionjedi.com/index.cfm/2006/4/24/ColdFusion-and-Pagination. No Query of Query is needed.
To answer your question
The problem is I can't return two
variables in the same cfinvoke tag.
WHY do you want to return two variables in the same cfinvoke? Instead, write 2 functions: countResult() and getResultData(page, RecordsPerPage)
<cffunction name="countResult" output="false" returntype="numeric">
<cfset var resultCount = "">
<cfquery name="resultCount" datasource="myDSN">
SELECT COUNT(gameID) AS rowsFound FROM GAMES
<!---JOINS FOR GENRE/PLATFORM GO HERE--->
WHERE
<!---CONDITIONS GO HERE--->
</cfquery>
<cfreturn resultCount.rowsFound>
</cffunction>
For getResultData(page, RecordsPerPage) using true paging in DB level:
If you want to do true pagnation in DB level, use LIMIT and OFFSET in MySQL.
<cffunction name="getResultData" output="false" returntype="Query">
<cfargument name="page" type="numeric" default="1">
<cfargument name="recordsPerPage" type="numeric" default="5">
<cfset var resultData = "">
<cfset var offset = (page-1) * RecordsPerPage>
<cfquery name="resultData" datasource="myDSN">
SELECT * LIMIT #recordsPerPage# OFFSET #offset#
<!---JOINS FOR GENRE/PLATFORM GO HERE--->
WHERE
<!---CONDITIONS GO HERE--->
</cfquery>
<cfreturn resultData>
</cffunction>
To figure out how many pages there are:
totalNumOfPages = ceiling(countResult() / recordsPerPage);
Any other question?

Answer 2

Rather than have two functions and two database calls, I've done it like this before (not in MySQL however):
<cffunction name="getResultData" output="false" returntype="Query">
<cfargument name="page" type="numeric" default="1">
<cfargument name="recordsPerPage" type="numeric" default="5">
<cfset var resultData = "">
<cfset var offset = (page-1) * RecordsPerPage>
<cfquery name="resultData" datasource="myDSN">
SELECT *,
(
SELECT COUNT(gameID) AS rowsFound
FROM
<!---JOINS FOR GENRE/PLATFORM GO HERE--->
WHERE
<!---CONDITIONS GO HERE--->
) AS rowsFound
LIMIT #recordsPerPage# OFFSET #offset#
<!---JOINS FOR GENRE/PLATFORM GO HERE--->
WHERE
<!---CONDITIONS GO HERE--->
</cfquery>
<cfreturn resultData>
</cffunction>
It adds a column to the returned recordset called 'rowsFound'.
Not very normalized, but not a big deal. Might be worth it to minimize the DB hits.
I think it's referred to as 'subquery as a scalar operand':
http://dev.mysql.com/doc/refman/5.1/en/scalar-subqueries.html
Tony