[datatable-help] Memory issue
Matthew Dowle
mdowle at mdowle.plus.com
Wed Oct 17 11:57:26 CEST 2012
And perhaps see if the file size increase can be demonstrated with
head(datMod,100)? If so, the smaller object could be attached to a bug
report so I can reproduce.
>
> Very interesting, thanks. I've not seen anything like this before. Perhaps
> some kind of UTF-8/ASCII conversion somewhere?
>
> Next step, please run and send output of :
>
> load('test0.Rdata')
> Small = copy(datMod)
> load('test1.Rdata')
> Large = copy(datMod)
> mapply(identical,Small,Large)
> mapply(all.equal,Small,Large)
> .Internal(inspect(Small))
> .Internal(inspect(Large))
>
> Also if you do the setkey on any int column (rather than chr), does that
> also increase the file size?
>
>> Matt
>>
>> I made a much simpler example that only involves the first data.table
>>
>> Also, although I had a POSIX date before, this example just has the text
>> for the date.
>>
>> It appears that the longer text columns are causing a problem.
>>
>> I'm saving as an RData file, and I also try using Rds at the end, but
>> with
>> no difference.
>>
>> Now I'm more convinced that the problem is in data.table, but I'm not
>> ruling out user error.
>>
>>> ## I was able to reproduce a simpler example
>>> ## without the second data.table
>>>
>>> ## Here is the data (with generic column names)
>>> str(datMod)
>> Classes data.table and 'data.frame': 3103314 obs. of 41 variables:
>> $ char1 : chr "http://conradhotels3.hilton.com" "
>> http://conradhotels3.hilton.com" "http://conradhotels3.hilton.com" "
>> http://conradhotels3.hilton.com" ...
>> $ char2 : chr "/en/index.html" "/en/index.html" "/en/index.html"
>> "/en/index.html" ...
>> $ char3 : chr "" "" "" "" ...
>> $ int1 : int 44903 44903 44903 44903 44903 44903 44903 44903 44903
>> 44903
>> ...
>> $ int2 : int 411 411 254 254 336 336 118 118 386 386 ...
>> $ char4 : chr "2012-05-09 20:17:40.587" "2012-05-09 21:17:54.427"
>> "2012-05-09 20:10:49.560" "2012-05-09 21:11:05.107" ...
>> $ int3 : int 0 0 0 0 0 0 0 0 0 0 ...
>> $ int4 : int 0 0 0 0 0 0 0 0 0 0 ...
>> $ int5 : int 69 69 69 69 69 69 69 68 68 68 ...
>> $ int6 : int 68 68 68 68 68 68 68 67 67 67 ...
>> $ int7 : int 35 35 37 35 35 35 33 38 38 40 ...
>> $ int8 : int 0 0 0 0 0 0 0 0 0 0 ...
>> $ int9 : int 0 0 0 0 0 0 0 0 0 0 ...
>> $ int10 : int 0 0 0 0 0 0 0 0 0 0 ...
>> $ int11 : int 1 1 1 1 1 1 1 1 1 1 ...
>> $ int12 : int 334830 334847 335102 334838 334836 342687 334521 318626
>> 318578 326800 ...
>> $ int13 : int 36 36 37 36 36 36 35 38 37 39 ...
>> $ int14 : int 44 44 49 47 45 45 45 46 45 48 ...
>> $ char5 : chr "" "" "" "" ...
>> $ int15 : int NA NA NA NA NA NA NA NA NA NA ...
>> $ int16 : int 0 0 0 0 0 0 0 0 0 0 ...
>> $ int17 : int 0 0 0 0 0 0 0 0 0 0 ...
>> $ int18 : int 2 2 2 2 2 2 2 2 2 2 ...
>> $ int19 : int 1381 1152 424 3728 1772 921 385 725 401 314 ...
>> $ int20 : int 36 36 37 36 36 36 35 38 37 39 ...
>> $ int21 : int 2199 2201 1492 1448 2559 2529 1084 1432 1876 1984 ...
>> $ int22 : int 44 44 49 47 45 45 45 46 45 48 ...
>> $ int23 : int 2203 2188 1199 1162 2324 2346 821 897 1386 1189 ...
>> $ int24 : int 13 13 14 13 13 13 12 13 13 14 ...
>> $ int25 : int 5166 5761 3755 3794 5614 7779 2830 3971 4637 5871 ...
>> $ int26 : int 103 103 105 103 103 103 101 105 105 107 ...
>> $ int27 : int 70 183 159 197 217 165 153 232 92 102 ...
>> $ int28 : int 103 103 105 103 103 103 101 105 105 107 ...
>> $ int29 : int 0 0 0 0 0 0 0 0 0 0 ...
>> $ int30 : int 161 146 200 158 150 160 190 161 163 169 ...
>> $ char6 : chr "Limelight" "Limelight" "Fusepoint/Savvis"
>> "Fusepoint/Savvis" ...
>> $ char7 : chr "Paris" "Paris" "Toronto" "Toronto" ...
>> $ char8 : chr "-1" "-1" "-1" "-1" ...
>> $ char9 : chr "FRANCE" "FRANCE" "CANADA" "CANADA" ...
>> $ char10: chr "FR" "FR" "CA" "CA" ...
>> $ char11: chr "FRANCE" "FRANCE" "CANADA" "CANADA" ...
>> - attr(*, ".internal.selfref")=<externalptr>
>>>
>>> ## Here is the size when you save that file
>>> save(datMod, file='test0.Rdata')
>>> originalfilesize = file.info('test0.RData')$size
>>> formatC(originalfilesize, big.mark=',', format='f', digits=0)
>> [1] "71,085,933"
>>>
>>> ## Here is the size after you set the key
>>> setkey(datMod, char4)
>>> save(datMod, file='test1.Rdata')
>>> newfilesize = file.info('test1.RData')$size
>>> formatC(newfilesize, big.mark=',', format='f', digits=0)
>> [1] "195,406,633"
>>>
>>> ## Some of the columns have a large size
>>> datMod[,range(nchar(char2))]
>> [1] 1 1606
>>> datMod[,range(nchar(char3))]
>> [1] 0 2048
>>>
>>> ## If I remove the long columns it helps reduce the file size
>>> datMod$char2 = NULL
>>> datMod$char3 = NULL
>>>
>>> save(datMod, file='test2.Rdata')
>>> secondfilesize = file.info('test2.RData')$size
>>> formatC(secondfilesize, big.mark=',', format='f', digits=0)
>> [1] "121,237,355"
>>>
>>> ## Using RDS doesn't matter
>>> saveRDS(datMod, file='test2.Rds')
>>> secondfilesizeRDS = file.info('test2.Rds')$size
>>> formatC(secondfilesizeRDS, big.mark=',', format='f', digits=0)
>> [1] "121,237,288"
>>
>
>
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