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loop fetch c into l_rec; exit when c%notfound; dbms_output.put_line( l_rec.username || '.....' ); end loop; close c; end; /

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The first function is the HelloWorld function; its definition is as expected: void CINTEROPDLL_API HelloWorld() { printf("Hello C world invoked by F#!\n"); } Say you now want to invoke the HelloWorld function from an F# program You simply have to define the prototype of the function and inform the runtime how to access the DLL and the other information needed to perform the invocation The program performing the invocation is the following: open SystemRuntimeInteropServices module CInterop = [<DllImport("CInteropDLL", CallingConvention=CallingConventionCdecl)>] extern void HelloWorld() CInteropHelloWorld() The extern keyword informs the compiler that the function definition is external to the program and must be accessed through the PInvoke interface A C-style prototype definition follows the keyword, and the whole declaration is annotated with a custom attribute defined in the SystemRuntimeInteropServices namespace.

Procedure created ops$tkyte%ORA11GR2> ops$tkyte%ORA11GR2> exec NOT_inj(sysdate) select * from all_users where created = :x PL/SQL procedure successfully completed It is a plain and simple fact that if you use bind variables you can t be subject to SQL injection If you do not use bind variables, you have to meticulously inspect every single line of code and think like an evil genius (one who knows everything about Oracle, every single thing) and see if there is a way to attack that code I don t know about you, but if I could be sure that 999999 percent of my code was not subject to SQL injection and only had to worry about the remaining 0.

0001 percent (that couldn t use a bind variable for whatever reason), I d sleep much better at night than if I had to worry about 100 percent of my code being subject to SQL injection In any case, on the particular project I began describing at the beginning of this section, rewriting the existing code to use bind variables was the only possible course of action The resulting code ran orders of magnitude faster and increased many times the number of simultaneous users that the system could support And the code was more secure the entire codebase did not need to be reviewed for SQL injection issues However, that security came at a high price in terms of time and effort, because my client had to code the system and then code it again.

The F# compiler adopts C-style syntax for extern prototypes, including argument types (as you ll see later), because C headers and prototypes are widely used, and this choice helps in the PInvoke definition The DllImport custom attribute provides the information needed to perform the invocation The first argument is the name of the DLL containing the function; the remaining option specifies the calling convention chosen to make the call Since not specified otherwise, the runtime assumes that the name of the F# function is the same as the name of the entry point in the DLL It is possible to override this behavior using the EntryPoint parameter in the DllImport attribute It is important to note the declarative approach of the PInvoke interface There is no code involved in accessing external functions The runtime interprets metadata in order to automatically interoperate with native code contained in a DLL.

It is not that using bind variables is hard, or errorprone, it s just that they did not use them initially and thus were forced to go back and revisit virtually all of the code and change it My client would not have paid this price if the developers had understood that it was vital to use bind variables in their application from day one..

The hash cluster query took the same amount of CPU for all intents and purposes, even though it went to the buffer cache one-third as many times. This, too, could be anticipated. The act of performing a hash is very CPU-intensive. The act of performing an index lookup is I/O-intensive. It was a tradeoff. However, as we scale up users, we would expect the hash cluster query to scale better, as it has to get in line to access the buffer cache less frequently.