On Wed, Nov 16, 2005 at 10:22:42AM +0000, Robin Breathe wrote:
> Nathan Kurz wrote:
> > I'm using a computationally expensive user defined function called
> > 'match()'. In case it makes a difference, match() is written in C,
> > and for testing, I'm loading it as a shared library into the sqlite3
> > shell application. I want to return the value of match(), and also
> > order by it. So my query looks something like this:
>
> Nathan,
>
> I'm intrigued to know how you loaded the additional shared library with
> your sqlite3(1) shell... is it simply a case of linking another library
> to it post installation, and if so how do you register the user
> functions that library contains?
Hi Robin ---
Unfortunately it's not a capability that comes built in. I wrote a
simple patch to add 'pragma load_library(library)' that will
dynamically load a library and then call a register function in that
library. It's not complicated, but I presume my implementation is
Linux specific. But it wouldn't be hard to do for other platforms.
The patch is attached, in case it helps you or anyone else. I think
this would be a useful feature to add to SQLite, but I can also see
how it might be considered feature creep. One might also need a
greater level of platform specific handling than used in the rest.
But if you are using Linux and need the capability, try the patch!
--nate
--- src/pragma.c~ 2005-09-20 11:42:23.000000000 -0600
+++ src/pragma.c 2005-11-12 10:07:10.000000000 -0700
@@ -918,6 +918,34 @@
}else
#endif
+#define SQLITE_PRAGMA_LOAD_LIBRARY
+#ifdef SQLITE_PRAGMA_LOAD_LIBRARY
+#include <dlfcn.h> /* NOTE: also must add -ldl to LIBS in Makefile */
+ /*
+ ** PRAGMA load_library(<library>)
+ **
+ ** Dynamically load a shared library. After loading, the function
+ ** 'sqliteRegister(sqlite3 *db)' is searched for in the new library
+ ** and called to allow that library to register user-defined functions.
+ */
+ if( sqlite3StrICmp(zLeft, "load_library")==0 && zRight ){
+ void *pHandle;
+ void (*pRegisterFunc)(sqlite3 *);
+ pHandle = dlopen(zRight, RTLD_LAZY);
+ if ( pHandle == 0 ) {
+ sqlite3ErrorMsg(pParse, dlerror());
+ goto pragma_out;
+ }
+ pRegisterFunc = dlsym(pHandle, "sqlite3Register");
+ if ( pRegisterFunc == 0 ) {
+ sqlite3ErrorMsg(pParse, "Could not find function "
+ "'sqlite3Register' in %s\n", zRight);
+ goto pragma_out;
+ }
+ pRegisterFunc(db);
+ }
+#endif
+
{}
if( v ){
