Thanks, Rick - definitely something to think about. I've been
troubled by the pagination stuff in our code. This looks like
something I can definitely use!
On 9/5/12 2:40 PM, Rick James wrote:
> Remember where you "left off".
> Your "Next" button now says something like ?page=5&size=50
> When you get there, you are doing something like SELECT ... ORDER BY ... LIMIT 250,
> Make it say ?after_id=12345&size=50
> and then do SELECT ... WHERE id > 12345 ORDER BY ... LIMIT 51
> With 51, you get 3 things:
> * the 50 items (or fewer) for the page
> * a clue that there will be a "Next" page
> * the id of the first item for that Next page
> 'Exercises for the reader':
> * 'Prev'
> * each of the next 5
> * each of the previous 5
> * go to last page
> * go to first page
> * Knowing whether to have those links or 'gray them out'.
> A sample UI layout (you've probably seen web pages like this):
> GoTo Page  ...   15   ... [last]
> *  represents a link.
> * You are currently (for this example) on page 15
> * It is showing you only the Next/Prev 2 pages.
> I have encountered multiple cases where a "crawler" (eg, search engine) brought a
> site to its knees because of "pagination via OFFSET".
> "Pagination via OFFSET" is Order(N) to fetch a page; Order(N*N) to scan the entire
> list. The first page takes 1 unit of effort. The second takes 2; etc. By the time the
> entire list has been paged through, about N*N/2 units of work have been done.
> My technique is Order(1) for a page, Order(N) for a complete scan.
> N is the number of pages. Some implementations have more than 10,000 pages. 10,000
> * 10,000 = 100 million !
>> -----Original Message-----
>> From: Andy Wallace [mailto:awallace@stripped]
>> Sent: Wednesday, September 05, 2012 2:05 PM
>> To: mysql@stripped
>> Subject: Re: Understanding Slow Query Log
>> Ok, this raises a question for me - what's a better way to do
>> On 9/5/12 2:02 PM, Rick James wrote:
>>> * LIMIT 0, 50 -- are you doing "pagination" via OFFSET? Bad idea.
>> Andy Wallace
>> iHOUSEweb, Inc.
>> (866) 645-7700 ext 219
>> "Sometimes it pays to stay in bed on Monday, rather than spending the
>> rest of the week debugging Monday's code."
>> - Christopher Thompson
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