write.odbc.ffdf: Write ffdf data to a database table by using a ODBC connection.

Description

Write ffdf data to a database table by using a ODBC connection. This can for example be used to store large ffdf datasets from R in Oracle, SQLite, MySQL, PostgreSQL, Hive or other SQL databases. Mark that for very large datasets, these SQL databases might have tools to speed up by bulk loading. You might also consider that as an alternative to using this procedure.

Usage

write.odbc.ffdf(
  x,
  tablename,
  odbcConnect.args = list(dsn = NULL, uid = "", pwd = ""),
  RECORDBYTES = sum(.rambytes[vmode(x)]),
  BATCHBYTES = getOption("ffbatchbytes"),
  by = NULL,
  VERBOSE = FALSE,
  ...
)

Arguments

the ffdf to write to the database

tablename

character string with the name of the table to store the data in. Passed on to sqlSave.

odbcConnect.args

a list of arguments to pass to ODBC's odbcConnect (like dsn, uid, pwd). See the examples.

RECORDBYTES

optional integer scalar representing the bytes needed to process a single row of the ffdf

BATCHBYTES

integer: bytes allowed for the size of the data.frame storing the result of reading one chunk. See documentation in read.table.ffdf for more details.

integer passed on to chunk indicating to write to the database in chunks of this size. Overwrites the behaviour of BATCHBYTES and RECORDBYTES.

VERBOSE

logical: TRUE to verbose timings for each processed chunk (default FALSE).

...

optional parameters passed on to sqlSave

Value

invisible()

Details

Opens up the ODBC connection using RODBC::odbcConnect, writes data to the SQL table using RODBC::sqlSave by extracting the data in batches from the ffdf and appending them to the table.

Examples

Run this code

# NOT RUN {
##
## Using the sqlite database (smalldb.sqlite3) in the /inst folder of the package
## set up the sqlite ODBC driver (www.stats.ox.ac.uk/pub/bdr/RODBC-manual.pd) 
## and call it 'smalltestsqlitedb' 
##
# }
# NOT RUN {
require(RODBC)
x <- read.odbc.ffdf(
  query = "select * from testdata limit 10000",
  odbcConnect.args = list(
   dsn="smalltestsqlitedb", uid = "", pwd = "", 
   believeNRows = FALSE, rows_at_time = 1), 
  nrows = -1, 
  first.rows = 100, next.rows = 1000, VERBOSE = TRUE)
  
write.odbc.ffdf(x = x, tablename = "testdata", rownames = FALSE, append = TRUE,
  odbcConnect.args = list(
   dsn="smalltestsqlitedb", uid = "", pwd = "", 
   believeNRows = FALSE, rows_at_time = 1),  
  by = 1000, VERBOSE=TRUE)
# }