Peek and Concatenate missunderstanding

[Anonymous]

Hello,  I have a little problem that I think that comes from the misunderstanding of the Concatenate or Peek functions. As far as I know those functions do:

    Concactenate (Old_Table): Used when loading a table this adds the rows of the new tabla at de end of (in the last position) the Old_Table to create the New_Table.

    Peek(Field): Written this way, this function returns the value of the last row of the new table.

Given This, suppose that I have a Table named "Old Table"  whit data of some product that includes sn (Serial Number) , date (Timestamp), and Color. What I want is to Concatenate Table_With_Duplicates to it so i use a where statement with peeks to check if the last row value is the same as the new one I want to introduce and discard it.

My code:

Concatenate(Old_Table):
load *
Resident Table_Sorted_With_Duplicates wherenot(peek(date)=date and sn=peek(sn) and COLOR=peek(COLOR));
drop table Table_Sorted_With_Duplicates;

With this code, when on the old table still there but if I create first a table without duplicates and then concatenate it works:

NoConcatenate

Table_Clean:

load *
Resident Table_Sorted_With_Duplicates wherenot(peek(date)=date and sn=peek(sn) and COLOR=peek(COLOR));
drop table Table_Sorted_With_Duplicates;

Concatenate(Old_Table):

load *
Resident Table_Clean;

drop table Table_Clean;

My point is that there is something that I misunderstand abount the Concatenate function on QV and when you use it the new rows are not added at the end of the table where the peek is checking. 

I provide you an example to test it. Also, I have testested with peek( Variable, 1)  in order to know if the values are added on the top an does not have worked.

[Anonymous]

This is True and I did not have noticed about that. Also I checked that if you use peek( Field, 1 ) taking the first value the ones that are not there are S1, D1 that are the ones in the first place.

This makes me think in 2 possibilities:

    1- The QV is inserting the data on some strange place in the middle (and I would like to find where)

    2- Maybe, doing the peek on the while statement is looking at the Old_Table, but not the concatenation

Anyway, thank you for your comments.

[Anonymous · Accepted solution]

Hello, I think I Find out what is really happening.

The Way QV does the concatenate is not ROW by ROW unless it must do it this way. If is possible for the QV just adds the whole table with one step and then checks the where condition after it. It is easy to see that if the that this consumes much less memory and is faster than do it row by row.

This process is like if it was pasting the memory location of the first row just after the last row of the previous table in order to start with the new one.

This does not happen if there is a calculated field on the load, then the QV is forced to create it row by row.

Event though I marked this answer as the correct (because is the one that answers the question), If someone reads this searching for a way to eliminate duplicates, please, read the answers of the other people, among them there are pretty good ways to do it.