Could you please try with the dev version?

hadley.
can you please provide me with a link to the dev version? i am only seeing for windows binaries (here : http://cran.r-project.org/web/packages/RMySQL/index.html) and i run GNU-linux.

https://github.com/rstats-db/RMySQL ...

thanks. i will give it a go in the next couple of days.

Was a solution to this every figured out? (I am trying to solve a similar problem with the same error message.)

@noktilux: Any updates here?

@MJFitzpatrick86: Could you please post a reproducible example?

I am facing the same problem. Trying to fetch data for thousand companies in a loop. After 30-40 companies it generates the above error. Even dev version has this issue. I get the following error

Error in validObject(.Object) :
invalid class "MySQLResult" object: invalid object for slot "Id" in class "MySQLResult": got class "character", should be or extend class "integer"

I had to use version 0.9.3. But that version sometimes generates "caught segfault" error.

@realgithup we can't help with a reproducible example

This is a real bug although it does seem to be one of those nasty "sometimes" errors. I got this error running an R script and then re-ran the same script on the same machine, absolutely no changes, no restarting MySQL, and it worked just fine.

Hi,
This is a very strange situation. I have exactly the same error and it's very hard to reproduce.
If I run the exact same query outside my script, it runs without any error and I can't get why.
So I'm not able to create a test case.

I dont know if this can help : if I add the line "dbColumnInfo(con, table) just before the call to the dbGetQuery call, the query is executed without any error (with table=the table used in dbGetQuery).

SessionInfo():
R version 3.2.1 (2015-06-18)
Platform: x86_64-redhat-linux-gnu (64-bit)
Running under: Red Hat Enterprise Linux Server release 6.3 (Santiago)

locale:
[1] LC_CTYPE=fr_FR.UTF-8 LC_NUMERIC=C
[3] LC_TIME=fr_FR.UTF-8 LC_COLLATE=fr_FR.UTF-8
[5] LC_MONETARY=fr_FR.UTF-8 LC_MESSAGES=fr_FR.UTF-8
[7] LC_PAPER=fr_FR.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=fr_FR.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] methods stats graphics grDevices utils datasets base

other attached packages:
[1] RColorBrewer_1.1-2 ggplot2_2.0.0 RMySQL_0.10.8 DBI_0.3.1
[5] Cairo_1.5-9

Best.

@cturbelin: Thanks. The R code and a dump of the database schema could help narrow down this issue.

@cturbelin: Confirmed that your dbColumnInfo hack worked in my case, too.

I have been seeing this error on Mac OSX once in a while when I was running repetitive big queries.

R> sessionInfo()
R version 3.2.3 (2015-12-10)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
Running under: OS X 10.11.3 (El Capitan)

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] devtools_1.10.0

loaded via a namespace (and not attached):
[1] tools_3.2.3   memoise_1.0.0 digest_0.6.9

But, when I moved to a Docker container running Debian 8.3, one of those repetitive big queries never worked. Same database server...

> sessionInfo()
R version 3.2.4 Revised (2016-03-16 r70336)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Debian GNU/Linux 8 (jessie)

locale:
[1] C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

When I called the dbColumnInfo once before the mentioned series of queries (I mean only once), it managed to get through without any problems.

PS: The R routine is basically iterating over a stock symbols vector of length ~8000, and issuing an SQL query to retrieve their OHLC series from the database. Simple query, simple DB structure.

OK, I have experienced another problem which looks like related to this.

As mentioned in the my previous comment, we have been calling the DBI::dbColumnInfo before attempting to read from the database table. Snippet from the R routine:

[...]

## Blind hack:
print(DBI::dbColumnInfo(xdbi::getConnection(), "table1"))
print(DBI::dbColumnInfo(xdbi::getConnection(), "table2"))

## Read from table1 and table2 separately:
[...]

Yesterday, our system has stopped in the middle of the day with this error message, right after printing the output of the first DBI::dbColumnInfo output:

Error in .local(conn, statement, ...) :
  connection with pending rows, close resultSet before continuing
Calls: print ... .local -> dbSendQuery -> dbSendQuery -> .local -> .Call
Execution halted

(Why does the call trace state dbSendQuery twice, right?)

Now... I know that we are running state machines and such errors must be reproducable. However, same Docker image running on local machine worked fine with the same database dump.

Going back to the server experiencing the problem, I've added a print statement for debugging purposes and it worked everytime when the script is run:

[...]

## Blind hack:
print("What is going on?")
print(DBI::dbColumnInfo(xdbi::getConnection(), "table1"))
print(DBI::dbColumnInfo(xdbi::getConnection(), "table2"))

## Read from table1 and table2 separately:
[...]

(Yep, I am surprised, too.)

I have quickly checked the C code for a possible problem in result set management, but couldn't find any. It looks short, precise and perfectly fine.

Then guess what: I have removed the blind hack entirely (including the print statement), and it never gave me the error message which it used to produce 2 weeks ago.

I am entirely clueless and don't want to waste package contributors' time... Could you address some functions in R and/or C/++ code which I can play with and see if I can produce some meaningful debugging information?

I am running into a similar issue. When running a sequence of queries using DBI::dbGetQuery, I intermittenly get the Error in validObject(.Object) : invalid class “MySQLResult” object: invalid object for slot "Id" in class "MySQLResult": got class "list", should be or extend class "integer" error. It seems most likely it is the second of the queries that is failing, but not all the time.

Impressively, here the same "blind hack" worked.

I'm doing a big query with 5 left joins.
It only worked by doing dbColumnInfo(con, "table_name") in all 6 tables used in the large select query, like this:

[ ... ]
    exec = dbExecute(con, paste('use sample_', sample_number, ";", sep=""))
    print(dbColumnInfo(con, "table1"))
    dbColumnInfo(con, "table2")
    dbColumnInfo(con, "table3")
    dbColumnInfo(con, "table4")
    dbColumnInfo(con, "table5")
    dbColumnInfo(con, "table6")
    if (exec == 0) {
        if (sample_number == "00") {
            df_samples = dbGetQuery(con, large_query_with_joins)
            [ ... ]
        }
    }
[ ... ]

Similar issue. Same workaround solved it.

Executing via Rscript, I tried dbColumnInfo but this ends up with the following error:

Loading required package: methods
Error in .local(dbObj, ...) : 
  internal error in RS_DBI_getConnection: corrupt connection handle
Calls: dbColumnInfo ... dbClearResult -> dbIsValid -> dbIsValid -> .local -> .Call
In addition: There were 50 or more warnings (use warnings() to see the first 50)
Execution halted

In R terminal, the error is

Error in validObject(.Object) : 
  invalid class “MySQLResult” object: invalid object for slot "Id" in class "MySQLResult": got class "character", should be or extend class "integer"

or

Loading required package: methods
Error in dbFetch(rs, n = -1, ...) : 
  INTEGER() can only be applied to a 'integer', not a 'char'
Calls: dbGetQuery -> dbGetQuery -> dbFetch -> dbFetch -> .Call
In addition: There were 50 or more warnings (use warnings() to see the first 50)
Error in .local(dbObj, ...) : 
  INTEGER() can only be applied to a 'integer', not a 'char'
Calls: dbGetQuery ... dbClearResult -> dbIsValid -> dbIsValid -> .local -> .Call
Execution halted

Through some experiments, I find that when select * or select A, B, C, ... where * or the specified columns represent more than 144 DECIMAL columns, the error will occur.

When I adjust MySQL() to MySQL(fetch.default.rec = 10000) then the error is magically gone.

@renkun-ken The "adjust MySQL() to MySQL(fetch.default.rec = 10000) then the error is magically gone"
worked for me too. Thanks for finding a solution for what the RMySQL developers should have fixed long ago.

MySQL(fetch.default.rec = 10000) only works in RStudio, not in R terminal. The same code works fine in RStudio but crashes every time in R terminal. When the script is added to crontab, it crashes every time.