[datatable-help] Memory issue

[Gene Leynes]

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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