Structs As Query Indexes, Speed, And Rick Osborne
Posted September 13, 2006 at 8:02 PM
For those of you who follow my blog, you will know that Rick Osborne is the guy who comes in after I explain things and makes killer suggestions about how they can be done better. I recently gave a case study of how ColdFusion code can be optimized. It involved using the IndexOf() method of the ColdFusion query column object. Rick came in and suggested that using a Struct to create your own query-index would perform faster. As I am a man who likes to learn by doing, I thought I would put this to the test.
To test this, I query from a web statistics program. I am getting information from two tables: web_stats_hit and web_stats_session. Each "hit" in the hits table will have a session id in the session table. The session table also have a UUID column "session_id".
As I am trying to test the merging of two data sources, I am going to hit each table individually and then try to update one with matching values from the other. First I am grabbing the two different data sets:
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- <!--- Query for web hits. --->
- <cfquery name="qHit" datasource="...">
- SELECT
- h.id,
- h.date_created,
- h.web_stats_session_id,
- (
- ''
- ) AS session_id
- FROM
- web_stats_hit h
- </cfquery>
-
-
- <!--- Query for web sessions. --->
- <cfquery name="qSession" datasource="...">
- SELECT
- s.id,
- s.session_id
- FROM
- web_stats_session s
- </cfquery>
As I tried to explain earlier, for every qHit.web_stats_session_id, there is a matching session, such that for some combo, qHit.web_stats_session_id == qSession.id. And just to get an idea of the amount of data we are talking about:
qHit: 52,290 records
qSession: 34,753 records
That's a LOT of data to go through. Let's get our "test" on:
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- <cftimer label="IndexOf() Methodology" type="outline">
-
- <!--- Loop over the hit query. --->
- <cfloop query="qHit">
-
- <!---
- We want to find a matching session_id based
- on the session. Get index of matching row.
- --->
- <cfset intIndex = qSession[ "id" ].IndexOf(
- JavaCast( "int", qHit.web_stats_session_id )
- ) />
-
- <!--- Add one to index (to be ColdFusion friendly). --->
- <cfset intIndex = (intIndex + 1) />
-
- <!--- Check to see if we have an index. --->
- <cfif intIndex>
-
- <!--- We found the match, update the row. --->
- <cfset qHit[ "session_id" ][ qHit.CurrentRow ] =
- qSession[ "session_id" ][ intIndex ]
- />
-
- </cfif>
-
- </cfloop>
-
- </cftimer>
-
- <cftimer label="Struct Index Methodology" type="outline">
-
- <!--- Create a session look up table. --->
- <cfset objSessionLookUp = StructNew() />
-
- <!---
- Loop over session and set index rows. We will be using
- the id column of the session as the key and the
- session_id as the value. This creates our very own,
- in-memory index of the qSession query based on ID.
- --->
- <cfloop query="qSession">
-
- <!--- Index this value. --->
- <cfset objSessionLookUp[ qSession.id ] = qSession.CurrentRow />
-
- </cfloop>
-
-
- <!--- Loop over the hit query. --->
- <cfloop query="qHit">
-
- <!---
- Check to see if the session key exists. If it
- does, then we found a match.
- --->
- <cfif StructKeyExists(
- objSessionLookUp,
- qHit.web_stats_session_id
- )>
-
- <!--- Update the session based on the struct-index. --->
- <cfset qHit[ "session_id" ][ qHit.CurrentRow ] =
- objSessionLookUp[ qHit.web_stats_session_id ]
- />
-
- </cfif>
-
- </cfloop>
-
- </cftimer>
It turns out Rick was absolute correct. The struct index performs MUCH faster. Here are the stats:
IndexOf() Methodology : 402,037 ms
Struct Index Methodology : 33,403 ms
Some quick math will show you that the struct index method performs in 8% of the time that the IndexOf() methodology does. EIGHT PERCENT! Nuts. I guess the only downside is that you can potentially create a HUGE in-memory structure; but it's only temporary.
Nicely done Rick!
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I figured you'd appreciate this:
http://rickosborne.org/images/screenshots/wtg-ben.png
That graph represents the last week's traffic to my site. This site has accounted for 3% of the traffic to my site, behind only Google and MXNA.
Rick,
That's awesome :) Glad to be sending people to you. You have good information to share.
