[R] dbHasCompleted() always returns TRUE for POSTGRES Database with RJDBC?

[julian.bothe at elitepartner.de]

Hello Simon, Hello everyone,

I have a problem with retrieving database-queries chunkwise. In my query
(Postgresql-Database,  Postgres-Version 9.1) dbHasCompleted seems to
always return TRUE. 

dbGetQuery works for smaller tables, but not for the whole query, since
then a Heap-Overflow-Error will occur (and a Error:
"java.lang.OutOfMemoryError: GC overhead limit exceeded" when trying to
set a larger size).

Does anybody else have or had this problem?

 

All the best

Julian

 

######## adapted Example from help (?dbHasCompleted ), Works #######

require("RSQLite")
 
con <- dbConnect(RSQLite::SQLite(), ":memory:")
dbWriteTable(con, "mtcars", mtcars)
 
# Fetch all results
res <- dbSendQuery(con, "SELECT * FROM mtcars WHERE cyl = 4")
dbFetch(res)
dbClearResult(res)
 
# Fetch in chunks
res <- dbSendQuery(con, "SELECT * FROM mtcars")
dbHasCompleted(res) ## RETURNS FALSE !!!
 
while (!dbHasCompleted(res)) {
  chunk <- fetch(res, 10)
  print(nrow(chunk))
}
dbClearResult(res)
dbDisconnect(con)

 

 

########## My Code, lamentably not reproducible because of needed
Postgres-Server, not working #########

 

# Connect to Postgres-Database 

res2 <- dbSendQuery(Postgres_con, 

                   "select  id from mytable limit 1000;"       

)

 

dbHasCompleted(res2) ##RETURNS TRUE!

 

while (!dbHasCompleted(res2)) {

  chunk <- fetch(res2, 10 )

  rbind(dk, chunk)

}

 

try({

  dbClearResult(res2)

  rm(chunk,res2)

})


	[[alternative HTML version deleted]]