[support] CCK fields being created as separate tables in the db

[Alex Tang]

Another way that a field is placed into a separate table is if that 
field ("hobbies" or "favourite music genres") have been added to more 
than one table.

When you add or remove a field from a table, CCK will alter the DB 
tables on the fly and move the data into and out of your tables.  I was 
at the boston drupalcon and worked with KarenS at the sprint, she talked 
about how this works and that it's a bit ugly inside.

She also mentioned that although it may seem that having the field data 
in separate tables may seem like a significant performance hit, after 
doing some testing, it's not as bad as you'd think due to the way cck 
does caching.  I didn't fully understand at the time, but after poking 
around the code a bit, i can see how that might be so.

...alex...




Gordon Heydon wrote:
> Hi,
>
> Yes this is correct, and there have been some people that will tell you 
> to use multiple and shared fields as little as possible as it is a 
> performance impact.
>
> I have recently discovered that this is not true. All fields not matter 
> what the type all have basically the same performance impact.
>
> The basic rule with CCK is to keep the total numbers of fields per node 
> as few as possible.
>
> I have fixed this in Drupal 5, and just need to clean up the patch 
> before I submit it.
>
> Gordon.
>
> Neil: esl-lounge.com wrote:
>   
>> OK, I found the answer in the second half of this article on the db 
>> aspects of CCK:
>>  
>> http://www.lullabot.com/articles/an_introduction_to_the_content_construction_kit
>>  
>> the two fields (which were actually hobbies and favourite music genres 
>> now I recall...) both accepted multiple values so it seems that is the 
>> crucial factor in deciding whether a CCK field gets added to the db as a 
>> separate table or part of a content type table: that - and whether the 
>> field is shared between content types.
>>  
>> Neil
>>
>>     ----- Original Message -----
>>     *From:* Neil: esl-lounge.com <mailto:neil at esl-lounge.com>
>>     *To:* support at drupal.org <mailto:support at drupal.org>
>>     *Sent:* Friday, March 21, 2008 10:16 AM
>>     *Subject:* [support] CCK fields being created as separate tables in
>>     the db
>>
>>     I've been pulling my hair out about this for two hours. I have made
>>     a nodeprofile content type and am using cck fields to build it.
>>
>>     All the fields I created were added as columns to the
>>     content_type_nodeprofile table....except the last two which were
>>     added to my db as separate tables:
>>
>>     content_field_hobbies
>>     content_field_age
>>
>>     these were the last two I added and, also, I had a few problems with
>>     the "group" they sat in, so I ended up changing the name and
>>     deleting and recreating the groups at least once...may this have
>>     caused the issue?
>>
>>     I've tried totally deleting the relevant fields and groups and
>>     starting again, but they keep getting created as separate tables. Aagh!!
>>
>>     Basically, what is it that makes CCK create a field as a separate
>>     table instead of putting it as a column inside the content type table?
>>
>>     Neil
>>
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>>
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