I have a table with values under a column named:str_condition
values in this column can be : variables.bit_male / application.bit_male / isdefined('session.int_user_id')
The value can be complex as it can be.
I need to use the value of the values in the column.
Currently, what I am doing is
<cfif evaluate(query.str_condition) eq true>
.....code....
</cfif>
Now, I need to omit the evaluate.
TBH, I'd stick with evaluate() for this: you're leveraging one of the few situations it makes sense. Provided what you have in the DB field is just an expression (no tags), then evaluate() will work fine.
As others have suggested... storing expressions in the DB is not ideal, but I can see how sometimes it might be the best approach, However do reconsider it though, in case you can come up with a different approach entirely (this is situation-specific, so we can't really give you guidance on that).
The only other real option for you would be to write the code from the DB to file then include it, but that would be a worse solution than just using evaluate(), I think.
A lot of people get hung up on the dogma that is evaluate() is bad, without really stopping to think about why that's the case... it's unnecessary for most situations people use it, but it's completely fine in situations in which it is needed (such as yours).
This is an edited answer, since I originally misread the question.
In many cases, array notation is your freind
<cfif queryname['fieldname'][rownumber] is true>
code for true
Note that the queryname is not quoted but the fieldname is. If you don't quote the fieldname, ColdFusion will assume it's a variable.
Also pertinent is that if you are storing things in a database, such as code, that you want to select and then execute, you have to select those things, write them to another .cfm file, and then cfinclude that file. That's somewhat inefficient.
In your case, you are storing variable names in your database. If using evaluate is giving you the correct results, anything you change would likely be a change for the worse.
How many unique combinations exist in the database? And do new values show up without developer interaction?
If it's a reasonable number of possible values that don't change then use a switch statement and write the line of code that handles each possible value.
<cfswitch expression="#query.str_condition#">
<cfcase value="variables.bit_male">
<cfset passed = variables.bit_male>
</cfcase>
<cfcase value="application.bit_male">
<cfset passed = application.bit_male>
</cfcase>
<cfcase value="isdefined('session.int_user_id')">
<cfset passed = isdefined('session.int_user_id')>
</cfcase>
<cfdefaultcase>
<cfset passed = false>
</cfdefaultcase>
</cfswitch>
<cfif passed>
.....code....
</cfif>
You don't have to hand write all of them, you can use a sql query to generate the repetitive part of the coldfusion code.
SELECT DISTINCT '<cfcase value="' + replace(table.str_condition,'"','""') + '"><cfset passed = ' + table.str_condition + '></cfcase>' as cfml
FROM table
ORDER BY len(str_condition), str_condition
If I am reading this correctly you are not just storing variable names in the database but actual snippets of code such as [ isDefined(session.it_user_id) ].
If this is what you are doing then you need to stop and rethink what you are trying to achieve. Storing code in your database and using evaluate to execute it is an incredibly bad idea.
It sounds to me like you are trying to create a generic code block that you can copy paste in multiple places and just set your conditional logic in the db.
The short answer is not to find a way around using evaluate but to stop storing code in your database full stop.
Related
This seems like a simple thing to do, but I am not having much luck in finding what I am looking for. I have a query that returns a single Id that I want to store as a variable. I am looking to see if there is a way to do that without using the <cfoutput> tag, as I guess it seems like I am not really outputting anything.
//declare variable
<cfset documentType = 0>
<cfquery datasource="mssql" name="GetDocType">
Select Id
From DocTypes
Where Description = 'MyType'
</cfquery>
I want to store the result of this query into the documentType variable. Again, I know it seems simple, but I have not seen any examples so far that really led me in the right direction. (Disclaimer, I am a .NET developer that has been given my first ColdFusion project in years - so this might be really really basic!)
This seems to work, but I am not sure if it's "Best Practice".
<cfset documentType = GetDocType.Id>
Since I know I will only have one row, I figured I could just reference the column that I want without having to do any looping.
If anyone has any other ideas or better ways, then let me know!
You would want to verify that .RecordCount is greater than 0 and the following:
<cfset documentType = GetDocType.Id[1]>
1 is the record number; I believe when not looping, that's how you access a particular row in a record set.
I develop using ColdFusion and wanted to know what is the best strategy to loop over large query result set. Is there any performance difference between using cfloop and cfoutput? If not, is there any reason to prefer one over the other?
I believe that there used to be. I think this difference has been tackled, the best bet is to do a test for each to test in you specific use case.
<cfset t = GetTickCount()/>
<cf... query="qry">
<!--- Do something --->
</cf...>
<cfset dt = GetTickCount() - t/>
<cfdump var="#dt#"/>
<!---
If the differences are small you can use java.lang.System.nanoTime() instead
--->
There are some notable differences though. cfoutput can do grouped loops, which cfloop cannot.
<cfoutput query="qry" group="col">
<!--- Loops once for each group --->
<cfoutput>
<!--- Loops once for each record within the group --->
</cfoutput>
</cfoutput>
For cfoutput you can specify the startrow and the maxrows (or the count) to paginate your result. For cfloop you have to specify the endrow index instead of the count.
Also you cannot use cfoutput for a query nested within an existing cfoutput tag, you will need to end the containing cfoutput first.
One good reason to use cfloop instead of cfoutput is if you need to loop a query output within another query output cfoutput does not support nested query outputting. You can however get away with it using cfloops. So:
<cfoutput query="test1">
#test1ID#
<cfoutput query="test2">
#test2ID#
</cfoutput>
</cfoutput>
does not work, but if you replace the cfoutputs with cfloops, it will.
As of CF10, with the ability to group cfloops, that's the only remaining functional difference. They both perform the same.
I believe it's all the same as performance, Ben Forta
And the rest is pretty much personal preference as far as how you "like" to work with your loop. Keep in mind you should always scope your variables, but inside a cfoutput loop that would be especially important since the query fields "could" be referenced without referring to their scope.
one reason you may prefer the cfloop approach would be if you needed to "escape" cfoutput during your loop for any reason. I have run into that several times, so I generally prefer cfloop.
There wouldn't be a performance difference using either method, it depends on your coding style really. If you put a <cfoutput> at the top and bottom of every page then using <cfloop> will work great. If you use multiple <cfoutput> and only place where they are needed that works as well.
I personally put <cfoutput> only where they are necessary, but I wouldn't say that's more correct than placing them at the top and bottom of the page.
I am building an application that performs a master query with many joins. This query data is then available to the whole application to play around with in a global variable. The query refreshes or gets the latest result set on each page refresh; so it's only in the same state for the life of the request.
In other parts of this application, I sometimes run 100's of QoQ's on this data - usually the result of recursive function calls. However, while QoQ is a great feature, it's not too fast and sometimes page loads can be between 3000 - 5000 ms on a bad day. It's just not fast enough.
Is there any kind of optimisation techniques I can do to make QoQ perform faster or perhaps an alternative method? I read an interesting article by Ben Nadel on Duplicate() function - is there any scope for using that and if so, how?
I would love to hear your thoughts.
Don't worry about crazy suggestions, this is a personal project so I'm willing to take risks. I'm running this on Railo compatible with CF8.
Many thanks,
Michael.
Without seeing the code and complexity of the QoQs it is hard to say for sure the best approach, however one thing you can do is use a struct to index the records outside of a QoQ. Much of the overhead of using QoQ is building new query objects, and using a struct write only approach is much more efficient than for example looping over the original query and making comparisons.
For example:
<!--- build up index --->
<cfset structindex = {} />
<cfset fields = "first,last,company" />
<cfloop list="#fields#" index="field">
<cfset key = "field:#field#,value:#q[field][currentrow]#" />
<!--- initialize each key (instead of using stuctkeyexists) --->
<cfloop query="q">
<cfset structindex[key] = "" />
</cfloop>
<cfloop query="q">
<!--- update each key with list of matching row indexes --->
<cfset structindex[key] = listappend(structindex[key], currentrow) />
</cfloop>
</cfloop>
<!--- save structindex to global variable --->
<!--- output rows matching index --->
<cfset key = "field:company,value:stackexchange" />
<cfoutput>
<cfloop list="#structindex[key]#" index="row">
#q.last[row]#, #q.first[row]# (#q.company[row]#)<br />
</cfloop>
</cfoutput>
If this doesn't match your need provide some examples of the QoQ statements and how many records are in the main query.
First, I would look at the time taken by the master query. If it can be cached for some mount of time and is taking a good chunk of the pageload time, I would cache it.
Next, I would look at the recursive calls. If they can be made iterative, that would probably speed things up. I realize this is not always possible. I would be surprised if this isn't your biggest time sink. without knowing more about what you are doing, though, it's hard to help you optimize this.
I might also consider writing some of the recursive QoQs s stored procedures on the DB server, which is designed to handle data quickly and slice and dice efficiently. CF is not -- QoQs are very useful, but not speed demons (as you've noted).
Finally, I would look for straightfoward filters, and not use QoQ. Rather, I would just run a loop over the master query in a standard cfoutput tag, and filter on the fly. This means you are looping over the master query once, rather than the master query once and the result query once.
There are two primary solutions here. First you could do something in CF with the records outside of QoQ. I posted my suggestion on this already. The other is to do everything in the db. One way I've found to do this is to use a subquery as a temp table. You can even keep the sql statement in a global variable and then reference it in the same places you are currently with the QoQ but doing a real query to the database. It may sound slower than one trip tothe DB and then many QoQ but in reality it probably isn't if indexed efficiently.
select *
from (
#sqlstring#
) as tmp
where company = 'stackexchange'
I have actually done this for system with complex criteria for both what records a user should have access to and then also what they can filter for in those records. Going with this approach means you always know the source of the inner records instead of trying to ensure every single query is pulling correctly.
Edit:
It is actually safer (and usually more efficient) to use queryparams when ever possible. I found this can be done by including a file of the sql statement...
select *
from (
<cfinclude template="master_subquery.cfm" />
) as tmp
where company = 'stackexchange'
Given a query (pseudo-code):
<cfquery name="myquery">SELECT * FROM stuff</cfquery>
How do I get rid of the first record? In this case, altering the SQL is not an option.
I have tried: myquery.RemoveRows(0,1); but received an error:
No matching Method/Function for Query.REMOVEROWS(numeric, numeric) found
I'm on Railo 3 BTW
Lo and behold:
myquery.RemoveRow(1);
Does exactly what I wanted. Leave it to Railo to do things a little differently!
Can't think of a way offhand to remove a row from the original object. Two things I can think of are:
do a query of queries. That assumes you'd be able to identify the records you don't want and specify them in the WHERE.
construct a new query with queryNew(). Loop over the original query doing a querySetCell() into the new query for the records that you want. This functionality could be incorporated into a UDF pretty easily. In fact, stating that made me think to check cflib.org. See #3
Check cflib.org :) See http://www.cflib.org/udf/QueryDeleteRows
"RemoveRows" is actually a call to the underlying Java method, so you have to cast those numbers. like so:
myquery.RemoveRows(
JavaCast( "int", 0 ) // starting row, zero-based
,JavaCast( "int", 1 ) // number to delete, returns error if too many
)
So probably the method is "int,int", and if you don't cast it, it looks like "numeric,numeric". One might argue that this is undocumented, but it's so succinct that you could (as I did) wrap it in a function, so that if it changes you just need to replace the contents of the function with an alternative workaround.
Railo has added removeRows, see here. My ACF code that uses this method now runs on Railo too, no changes.
With this, the Railo implementation now matches ACF. (Note also that the original Railo implementation was 0 based, while the new one and the ACF version are both 1 based.)
The way I would normally do it is with a query of queries such as the following:
SELECT * FROM myquery
LIMIT {1,10000}
That should work in Railo. What it does is offset the query by one and pulls 10000 records.
You could also do this:
SELECT * FROM myquery
WHERE {primarykey} <> {value}
Where it selects all records except for the primary key value that you pass in.
The awesome thing about ColdFusion is that there are tons of ways to do exactly what you are looking for.
You could just skip the row when you process the results:
<cfoutput query="myquery">
<cfif myquery.currentrow GT 1>
<!---Do the work here. --->
</cfif>
</cfoutput>
I would like to be able to do a query of a query to UNION an unknown number of recordset. However when doing a query-of-query dots or brackets are not allowed in record set names.
For example this fails:
<cfquery name="allRecs" dbtype="query">
SELECT * FROM recordset[1]
UNION
SELECT * FROM recordset[2]
</cfquery>
Using dynamic variable names such as "recordset1" work but this is in a function and needs to be var-scoped so I can't build up the variable names dynamically without producing memory leaks in a persisted object.
Any other ideas?
After posting the question I came up with a couple solutions but there might be a better one out there
I could write dynamically named variables to the arguments scope and then reference them without their scope in query
Create a function that accepts 2 recordsets as arguments and returns one combined recordset. This could be looped over to progressively add a recordset at a time. I'm sure this is very inefficient compared to doing all UNIONs in one query though.
Difficult task. I could imagine a solution with a nested loop based on GetColumnNames(), using QueryAddRow() and QuerySetCell(). It won't be the most efficient one, but it is not really slow. Depends on the size of the task, of course.
Your "create a function that combines two recordsets" could be made much more efficient when you create it to accept, say, ten arguments. Modify the SQL on the fly:
<cfset var local = StructNew()>
<cfquery name="local.union" dbtype="query">
SELECT * FROM argument1
<cfloop from="2" to="#ArrayLen(arguments)#" index="local.i">
<cfif IsQuery(arguments[local.i])>
UNION
SELECT * FROM argument#local.i#
</cfif>
</cfloop>
</cfquery>
<cfreturn local.union>
After a quick bit of poking around, I found this:
queryConcat at CFLib.org. It uses queryaddrow/querysetcell to concatenate two queries.
I added a quick function (with no error checking, or data validation, so I wouldn't use it as-is):
<cffunction name="concatenate">
<cfset var result = arguments[1]>
<cfloop from="2" to="#arraylen(arguments)#" index="i">
<cfset result=queryconcat(result, arguments[i])>
</cfloop>
<cfreturn result>
</cffunction>
As a test, I threw this together:
Which does, in fact, give you fred/sammy/fred.
It's probably not the most efficient implementation, but you can always alter the insert/union code to make it faster if you wanted. Mostly, I was aiming to write as little code as possible by myself. :-)
all of the solutions added here should work for you, but I would also mention that depending on how much data you are working with and the database you are using, you might be better off trying to find a way to do this on the database side. With very large record sets, it might be beneficial to write the records to a temporary table and select them out again, but either way, if you can in any way rewrite the queries to let the database handle this in the first place you will be better off.