How much memory is used by each of the following standard data types?
- Date
- Time
- Datetime
- Real
- Double
- Decimal
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- How much memory is used by certain standard PB data types?
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John Fauss
- PowerBuilder
- Wednesday, 20 February 2019 03:08 AM UTC
Hi John;
Well ... if memory serves me correctly (no pun intended here - LOL), that information is not well documented anywhere AFAIK. However, I do have a "sneaky" way to find out if you have some spare coding time. The DW object will actually give you that information via the command:
.Object.DataWindow.Storage // OR .Describe("DataWindow.Storage")
Now what you would need to do is create one "external" DW object with one row and one column of the datatype from your question ... say for example "Decimal". Then at run time load the DWO and perform an InsertRow(0) plus SetItem(1,
For example:
The above approach would not work though for native variables. You would have to instantiate say a Decimal variable and perform a "GlobalMemoryStatusEx" MS-Windows API call just before and after the variable type instantiation. The delta of course would be the native memory consumption for that variable type.
Sorry for that little bit of a long winded answer.
HTH
Regards ... Chris
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- John Fauss
- Tuesday, 26 February 2019 02:21 AM UTC
Roland, for the most part, I think it's reasonable that a Real is represented in 4 bytes, a Double in 8 bytes, Time and Date values each in 4 bytes, and a Datetime in 8 bytes. However, I can't see how a Decimal value, which has up to 28 digits, sign and decimal point position could be represented in only 8 bytes...16 bytes, likely.
In the end, I would just like to see Engineering document this information officially, once and for all. Thanks for your input!
In the end, I would just like to see Engineering document this information officially, once and for all. Thanks for your input!
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In general, inserting the first row incurs a non-trivial increase in storage use of approx. 1700-2700 bytes varying between the datatype of column object and presentation (visual vs. non-visual) , which is, I suppose, understandable. Subsequent row additions consistently increased storage use by a fairly small amount (in the range of 104-120 bytes, depending on the datatype). I also compared storage use when adding a row without setting a value versus performing a SetItem after the InsertRow. I cannot draw any definitive conclusions from the results, and I'm doubtful that a standard datatype such as Decimal, Date, Time, & Datetime require 104-120 bytes of memory.
I will look into your suggestion on using the GlobalMemoryStatusEx Windows API tomorrow evening. Thanks again for the suggestions!
Thanks for that feedback and your hard work ... very interesting!