takusen-oracle

Takusen Oracle is an Oracle access library

Monthly Downloads: 12

Programming language: Haskell

License: BSD 3-clause "New" or "Revised" License

Tags: Database    

Latest version: v0.9.4.2

README

Takusen Oracle is an Oracle access library. Like HSQL and HDBC, it supports arbitrary SQL statements (currently strings, extensible to anything that can be converted to a string). Takusen's unique selling point is safety and efficiency. We statically ensure all acquired database resources - such as cursors, connections, and statement handles - are released, exactly once, at predictable times. Takusen Oracle can avoid loading the whole result set in memory, and so can handle queries returning millions of rows in constant space. Takusen also supports automatic marshalling and unmarshalling of results and query parameters. These benefits come from the design of query result processing around a left-fold enumerator.

Installing

Prerequisites: GHC >= 7.6.3, Cabal >= 1.16

Using i.e. Writing data access code

There are extensive instructions and examples in the Haddock docs for module Database.Enumerator:

http://hackage.haskell.org/packages/archive/takusen-oracle/0.9.1/doc/html/Database-Enumerator.html

This should give you most, if not all, of the information you need to create a program that uses Takusen.

Here's a little hello-world test case that uses Oracle:

{-# LANGUAGE ScopedTypeVariables #-}
module Main where
import Database.Oracle.Enumerator
import Control.Monad.Trans (liftIO)
main = flip catchDB reportRethrow $
  withSession (connect "system" "system" "localhost/XE") (do
    let iter (s::String) (_::String) = result s
    result <- doQuery (sql "select 'Hello world.' from DUAL") iter ""
    liftIO (putStrLn result)
    )

If this is Main.hs, then

  $ ghc --make Main -o hello

should build a "hello" executable.

Paths, GHCi & runhaskell

Just as with ensuring that your path is correctly set when building Takusen, you must also ensure it is correctly set when building your programs. If it is not correct, then you are likely to see linker errors.

For successful building of the library, you should set Extra-Lib-Dirs to your Oracle home lib directory.

Oracle gotchas on Windows

Some users have reported linker errors because their Oracle bin contains hsbase.dll, which is an Oracle library related to Heterogenous Services. This DLL overrides GHC's HSbase.dll, and therefore causes linker errors.

If you can control your Oracle client installation then either

• don't choose Heterogenous Services when you install, or re-run the installer and remove it, or
• rename hsbase.dll in Oracle bin.