Creating temporary table

[Ruslan Zasukhin]

on 12/10/03 5:44 AM, Eric Forget at forgete at cafederic.com wrote:

>> I have explain, that Cursor will NOT have indexes!
>> 
>> So it is not a fact that search on cursor will be faster,
>> May be only if table is huge but selection is small.
> 
> I have a question about that. Is Cursor saved as an internal temporary table
> or all in RAM? (For both current and V2)

Hi Eric,

Cursor can be of different kinds.

1) if this is simple WHERE or even simple JOIN, this can be just RAM based
array of selected RecIDs.
    so iteration of records is made on original tables.


2) IF table have DISTINCT, or GROUP BY or AGGR funcs,
    we MUST CREATE TMP table.

    right now it is always on disk.

    in 2.0 we will try estimate its size, and tables with few records
    create on RAM.


3) also we hoping in 2.0 or 2.x implement TreeCursor or HierachicalCursor.
    you will not see difference.
    difference just in internal storage of data.

    although this class can have additional functions,
    it can be useful for effective XML generation.

    and in some cases it can be more effective that cursor from
    point 1. 

-- 
Best regards,
Ruslan Zasukhin      [ I feel the need...the need for speed ]
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e-mail: ruslan at paradigmasoft.com
web: http://www.paradigmasoft.com

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