Downloader behaviour - remove ; replace

Downloader behaviour - remove ; replace

saratur
2011-01-27 15:49:17

What is the exact behaviour of a Downloader for the four combinations of check/uncheck for
"remove old data"
and
"replace same data" ?

QuantShare
2011-01-28 05:04:38

Imagine your are downloading EOD data for Google:
"remove old data" instructs the application to remove Google EOD data before adding the new data
"replace same data" instructs the application to replace data for the same dates

saratur
2011-01-28 05:23:08

Sorry I am not clear on what exactly this means.
- "replace same data" - this would be for the start to end dates, correct?
- "remove old data" - if this relates to the start to end date range it seems this will be same as replace; so is it removing all the data for GOOG, including for dates outside of the range?
- what happens when none of these tow boxes is checked? does updates only dates where there was no earlier data?

QuantShare
2011-01-28 06:10:30

Best Answer

Example:
Current Goog data: (In the database)
01/01/2010;601.2;601.3
02/01/2010;601.2;601.3

Downloaded Goog data: (From the Internet)
02/01/2010;601.2;601.4
03/01/2010;601.2;601.3

If "remove old data" is checked then the application removes all Goog data before adding the new data (Including data outside the range).

If "replace same data" is checked then the first line (02/01/2010) will be updated (because it already exists) and (03/01/2010) will be added
Result:
01/01/2010;601.2;601.3
02/01/2010;601.2;601.4 <- This value was updated
03/01/2010;601.2;601.3

If "replace same data" is not checked then the first line (02/01/2010) is ignored and (03/01/2010) will be added
Result:
01/01/2010;601.2;601.3
02/01/2010;601.2;601.3
03/01/2010;601.2;601.3

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