CODEWITHSUNDEEP
haskellsql-server-2012hdbc
Thiago Negri
Thiago Negri

Reputation: 5351

HDBC-ODBC SQL Server need commit after quickQuery

I'm giving my first steps into HDBC using ODBC to connect to a local SQL Server.

After a quickQuery on the connection, I can't close it. I need to perform a commit first.

Is this the way it is supposed to be? Why is the commit necessary when I'm only performing a query?

On GHCi:

m + Database.HDBC Database.HDBC.ODBC
conn <- connectODBC "Driver={SQL Server};Server=thiagon\\sqlserver2012;Database=senior;UID=framework;PWD=framework;"
vals <- quickQuery conn "SELECT TOP 5 * FROM whatever;" []
print vals
commit conn
disconnect conn

If I remove the commit conn line, I get an exception: 

*** Exception: SqlError {seState = "[\"25000\"]", seNativeError = -1, seErrorMsg = "disconnect: [\"0: [Microsoft][ODBC SQL Server Driver]Estado de transa\\65533\\65533o inv\\65533lido\"]"}

The message is in portuguese, it means "invalid transaction state".

Upvotes: 3

Views: 724

Answers (1)

mhwombat
mhwombat

Reputation: 8136

A quickQuery could modify the table. I don't think the API analyses the string itself, or checks the database, to see whether or not the table was modified. And HDBC doesn't support autocommit.

You could use withTransaction, which will automatically handle this detail for you.

EDIT: Try using quickQuery', which is the strict version of quickQuery. In an example on http://book.realworldhaskell.org/read/using-databases.html (scroll down to ch21/query.hs), they didn't need a commit after a plain SELECT statement, but they were using quickQuery'.

Upvotes: 1

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