Erik,
Can you store the data as a blob? For example:
> #create string, compress with gzip, convert to SQLite blob string
> string <- "gzip this string, store as blob in SQLite database"
> string.gz <- memCompress(string, type="gzip")
> string.sqlite <- paste("x'",paste(string.gz,collapse=""),"'",sep="")
> #create database and table with a BLOB column
> library(RSQLite)
Loading required package: DBI
> con <- dbConnect(dbDriver("SQLite"), "compress.sqlite")
> dbGetQuery(con, "CREATE TABLE Compress (id INTEGER, data BLOB);")
NULL
> #insert the string as a blob
> query <- paste("INSERT INTO Compress (id, data) VALUES (1, ",
+ string.sqlite, ");", sep="")
> dbGetQuery(con, query)
NULL
> #recover the blob, decompress, and convert back to a string
> result <- dbGetQuery(con, "SELECT data FROM Compress;")
> string.gz <- result[[1]][[1]]
> string <- memDecompress(string.gz, type="gzip")
> rawToChar(string)
[1] "gzip this string, store as blob in SQLite database"
-Matt
On Fri, 2010-07-09 at 12:51 -0400, Erik Wright wrote:
> Hello,
>
> I would like to compress a long string (character vector), store the
> compressed string in the text field of a SQLite database (using RSQLite), and
> then load the text back into memory and decompress it back into the the
> original string. My character vector can be compressed considerably using
> standard gzip/bzip2 compression. In theory it should be much faster for me
> to compress/decompress a long string than to write the whole string to the
> hard drive and then read it back (not to mention the saved hard drive space).
>
> I have tried accomplishing this task using memCompress() and memDecompress()
> without success. It seems memCompress can only convert a character vector to
> raw type which cannot be treated as a string. Does anyone have ideas on how
> I can go about doing this, especially using the standard base packages?
>
> Thanks!,
> Erik
>
>
> > sessionInfo()
> R version 2.11.0 (2010-04-22)
> x86_64-apple-darwin9.8.0
>
> locale:
> [1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
>
> attached base packages:
> [1] stats graphics grDevices utils datasets methods base
>
> loaded via a namespace (and not attached):
> [1] tools_2.11.0
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
--
Matthew S. Shotwell
Graduate Student
Division of Biostatistics and Epidemiology
Medical University of South Carolina
http://biostatmatt.com
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