Would like to know how Import and Reload works

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Would like to know how Import and Reload works

Postby 2haerim » 04 Feb 2008

Let me restrict this issue to tick data only.

1) I export one day's ticks into A.txt from a symbol S after market closed. The # of ticks are 50000.
2) I import A.txt back into S without deleting any cache or ticks at all.
3) I expect the # of tikcs gets doubled. That is, 100000.
3) The result is surprisingly 50000 again.
4) From several experiments, I concluded Import ASCII first deletes ticks for the specifiec Import Range and then imports the ticks. So we don't have to worry about duplicate ticks being imported and no need to delete ticks before importing. Is this correct? Even if it is correct, still I am not sure what to do with cache when I import though. Do I have to clear cache at least or will QM take care everything for me so that no duplicate ticks are saved into QM nor plotted onto current charts or charts to be open after importing?

Next about Reload.

Reload downloads all the data for the range specified in the chart from the server. There can be two cases:
1) Server has full data for the specified range.
2) Server has no or partial data for the specified range.

Now for each of the above two cases, how does QM handle the existing data saved in QM's local storage? Delete it first and then download? This will be ok in case 1) because Server will fill up all the data again. But what if in case 2)? Will it wait until all the requested reloa data is received from the server? How long will it wait? Wha if the server does not respond? So many questions...

MC & QM are quite a big program and poses so many possibilities in so many situations. So without completely understanding how the basic things about data management is done, we would easily get lost when some strange chart, behavior or whatever happens.

So please describe in very detail how Reload works.
- Does it delete local data first before downloading from server? or download first and check if the server has enough data to reload? what if server does not have enough data or some missing data?

Reload feature needs more granular control such as reloading today only(maybe current session), just 1 hour, and so on because Reloading takes so much time and can cause so many troubles depending on the situations described above. As far as I know all traders only need to reload a very small portion of data(at most one day) when they are trading realtime. They need faster response. They could reload whole range of data when backtesting but it is also rare because they manage the data every day and they try very hard to make sure that they have correct data everyday.

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