Query large CSV file as a data source?

[Bob Sneidar]

Just read for 10,000 lines and check for empty each time. 

Bob S


> On Nov 3, 2020, at 7:09 AM, matthias rebbe via use-livecode <use-livecode at lists.runrev.com> wrote:
> 
> Regarding the loop.
> 
> you could do a
> 
> put the detailed files 
> 
> to get the file size of that csv file.
> 
> With that size you would now how often you have to run the loop
> 
> 
> 
> 
> 
> -
> Matthias Rebbe
> Life Is Too Short For Boring Code
> 
>> Am 03.11.2020 um 15:14 schrieb Keith Clarke via use-livecode <use-livecode at lists.runrev.com>:
>> 
>> Thank you Matthias, I wasn’t aware of that ability to open the file and read its contents straight from the disk. 
>> 
>> A quick experiment looks positive - no hanging and fast access - so I just need to work on the loop.
>> 
>> Much obliged.
>> 
>> Best,
>> Keith   
>> 
>>> On 3 Nov 2020, at 13:37, matthias rebbe via use-livecode <use-livecode at lists.runrev.com> wrote:
>>> 
>>> Couldn't you read the file partially
>>> 
>>> you would open the file for read
>>> 
>>> 	open file tFile for read
>>> 
>>> then in a repeat loop you could read e.g. 10000 lines and process the data
>>> 
>>> 	read from file tFile for 10000 lines
>>> 
>>> 
>>> Just a thought.
>>> 
>>> 
>>> -
>>> Matthias Rebbe
>>> Life Is Too Short For Boring Code
>>> 
>>>> Am 03.11.2020 um 13:14 schrieb Keith Clarke via use-livecode <use-livecode at lists.runrev.com>:
>>>> 
>>>> Hi folks,
>>>> I’ve a 3GB CSV file with 18M rows from which I need to create a subset CSV file for the rows containing tString. The following script results in LiveCode becoming unresponsive, so I’m wondering if I’m missing an obvious trick or what alternative approach I might take...
>>>> on mouseUp pButtonNumber
>>>> 
>>>> -- Select CSV File
>>>> 
>>>> answer file prompt as sheet
>>>> 
>>>> put it into tFile
>>>> 
>>>> put tFile into field "File"
>>>> 
>>>> -- Process CSV extract
>>>> 
>>>> put URL ("file:" & tFile) into tText
>>>> 
>>>> put line 1 of tText into field "List"
>>>> 
>>>> filter lines of tText with "*tString*"
>>>> 
>>>> put tText into field tList
>>>> 
>>>> end mouseUp
>>>> 
>>>> I don’t normally deal with large data sets, so maybe LiveCode isn’t the best tool for this but Excel 365 seems to only offer CSV file import, not query.
>>>> 
>>>> Any thoughts greatly appreciated.
>>>> 
>>>> Thanks & regards,
>>>> Keith
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>>> 
>>> 
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