Query large CSV file as a data source?

[Keith Clarke]

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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