DB examples corrupted? and other questions

[Richard Gaskin]

Monte Goulding wrote:

> I'm wondering if you have tested multi-dimensional arrays (stored as
> customproperty sets)? I think the direct access nature would kill
> tab-delimited text. What abut using something like: primaryKey,columnName as
> the array key? I think it could be very fast and handle much more data. In
> addition there is no risk from the delimiters.

True on all fronts. Random access of specific "records" (elements in an
array and lines in text) is much faster with arrays than with one block of
text.

However, in my case I settled on chunks because in nearly every usage I'm
displaying only a subset of columns, and usually more than one record, so I
need to query the whole data set each time.  In my benchmarks walking
through all the elements of an array is slower than walking through a text
block.

I don't have those benchmarks handy, but if I recall "repeat for each
element" took nearly twice as long as "repeat for each line".

Your code:
  
> on mouseUp
>   put the long seconds into tSeconds
>   set the itemDel to tab
>   put the cTest of this stack into tTest
>   repeat with x=0 to 10000 step 100
>     put item 25 of line x of tTest into tData
>   end repeat
>   put the long seconds - tSeconds into tTest1
>   put the long seconds into tSeconds
>   repeat with x=0 to 10000 step 100
>     put the cTest[x,25] of this stack into tData
>   end repeat
>   put the long seconds - tSeconds into tTest2
>   put tTest1,tTest2
> end mouseUp
> 
> Result 0.219,0.002

...uses the "repeat with" form, which is much slower than "repeat for each"
and doesn't scale well; it takes increasingly longer as you work your way
down through the lines, as it needs to count the number of lines each time
through the loop.  The "repeat for each line" form runs at a nearly constant
rate of lines per millisecond regardless of the size of the data set.

The "repeat for each" form parses and keeps its place as it goes, making it
many times faster for large text blocks.

-- 
 Richard Gaskin 
 Fourth World Media Corporation
 Developer of WebMerge 2.2: Publish any database on any site
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