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Topic: Maximum size of Random Access File (Read 694 times) |
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Richard Russell
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Re: Maximum size of Random Access File
« Reply #2 on: Apr 14th, 2016, 5:36pm » |
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on Apr 14th, 2016, 5:16pm, RobM wrote:| As your code proves, it is possible but exceedingly slow. |
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Creating a 5 Gbyte file from scratch is slow, but that's not what typically happens with a database. Once the file is created you should find that seeking and reading/writing is in fact exceedingly fast, and having a large, sparse, file may be easier than deriving the record number with a hash and having to deal with collisions.
With modern storage devices having typically hundreds of Gigabytes, or even Terabytes, of capacity I certainly wouldn't rule out using a RAF considerably bigger than 4 Gbytes. LBB is entirely suitable for that.
The real point I was trying to make is that LB 4 is very limiting. Having a 4 Gbyte file-size limit or a 32-bit record-number limit is not really acceptable in 2016. LBB has neither of those limits.
Richard.
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Richard Russell
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Re: Maximum size of Random Access File
« Reply #3 on: Apr 14th, 2016, 9:42pm » |
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on Apr 14th, 2016, 5:36pm, Richard Russell wrote:| Having a 4 Gbyte file-size limit or a 32-bit record-number limit is not really acceptable in 2016. |
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Chris Iverson writes at the Community Forum that "The file size parameter in many of the Win32 file access APIs is still 32-bit for compatibility reasons" but what APIs are those? GetFileSize, SetFilePointer and the WIN32_FIND_DATA structure have all been 64-bit-size compatible since at least Windows 95 - that's over twenty years!
Whatever the reason for LB 4 having a 4 Gbyte file-size limit might be, it's not that the Win32 API ever enforced it.
Richard.
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RobM
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Re: Maximum size of Random Access File
« Reply #4 on: Apr 14th, 2016, 10:29pm » |
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Chris recently mentioned that much of what he writes in regards to how LB works in the background is just speculation 
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Richard Russell
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Re: Maximum size of Random Access File
« Reply #5 on: Apr 15th, 2016, 10:03am » |
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on Apr 14th, 2016, 10:29pm, RobM wrote:| Chris recently mentioned that much of what he writes in regards to how LB works in the background is just speculation |
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Well indeed it must be, since only Carl knows what actually happens (and even he may not always know if it's buried within SmallTalk). Similarly any comments I make on the internal workings of LB are just intelligent guesses based on the symptoms and experience gained from writing LBB.
But in this case Chris was referring not to the internals of LB but to the Windows API. Claiming that many Win32 APIs support only a 32-bit file-size is, I'm afraid, plain wrong. Yes it can be easier to use a 32-bit size value, and I've done that many times myself (indeed it was a limitation of LBB pre v3.00), but it's not actually enforced by the API.
Richard.
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