Re: Query large CSV file as a data source?

[matthias rebbe via use-livecode]

> Am 03.11.2020 um 23:02 schrieb Bob Sneidar via use-livecode 
> <use-livecode@lists.runrev.com>:
> 
> Just read for 10,000 lines and check for empty each time. 
> 

To be honest, i've never used the read file for ... lines.
I was expecting that there might be an error if one tries to read more lines 
than there are left for read 
Good to know that one can just read in a loop without calculating the loop 
count first.


-
Matthias Rebbe
Life Is Too Short For Boring Code

> Bob S
> 
> 
>> On Nov 3, 2020, at 7:09 AM, matthias rebbe via use-livecode 
>> <use-livecode@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@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@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@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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