fmgr_oldstyle in extensions

[Paul Ramsey]

 
Hi all,

I’m trying to implement an spgist index in the PostGIS extension, which seems like it should work, but is thus far not working for what appear (to me) to be issues in the way spgist expects to pass pointers to user-defined functions.

Right before anything happens, spgist calls a ‘config’ routine in the user code. This is the code from the example implementation (which is internal to pgsql, not a run-time add-on like postgis)

 Datum
 spg_quad_config(PG_FUNCTION_ARGS)
 {
 /* spgConfigIn *cfgin = (spgConfigIn *) PG_GETARG_POINTER(0); */
 spgConfigOut *cfg = (spgConfigOut *) PG_GETARG_POINTER(1); 

 cfg->prefixType = POINTOID;
 cfg->labelType = VOIDOID; /* we don't need node labels */
 cfg->canReturnData = true;
 cfg->longValuesOK = false;
 PG_RETURN_VOID();
 }

It is called from the spgist core in the spgGetCache() function, via 

 FunctionCall2Coll(procinfo,
   index->rd_indcollation[0],
   PointerGetDatum(&in),
   PointerGetDatum(&cache->config));

The part the user function cares about is the pointer to cache->config. 

In the core code, the call stack to the user function goes like this:

postgres`spg_quad_config(fcinfo=0x00007fff5f0faf90) + 18 at spgquadtreeproc.c:29
postgres`FunctionCall2Coll(flinfo=0x00007ff59a804cc8, collation=0, arg1=140734788252568, arg2=140692835814944) + 150 at fmgr.c:1327
 postgres`spgGetCache(index=0x000000010254be68) + 220 at spgutils.c:71

So, spgGetCache to FunctionCall2Coll to spg_quad_config.

In my user-defined version of the same thing (I just copied the C code and wrote a CREATE OPERATOR CLASS for it) the call stack is this

postgis-2.2.so`gserialized_spgist_quadtree_2d_config(fcinfo=0x00007fff5f0fb398) + 30 at gserialized_spgist_2d.c:60
postgres`fmgr_oldstyle(fcinfo=0x00007fff5f0faf90) + 424 at fmgr.c:678
postgres`FunctionCall2Coll(flinfo=0x00007ff59a039cc8, collation=0, arg1=140734788252568, arg2=140692827643424) + 150 at fmgr.c:1327
postgres`spgGetCache(index=0x000000010254be68) + 220 at spgutils.c:71

So, spgGetCache to FunctionCall2Coll to fmgr_oldstyle to 
gserialized_spgist_quadtree_2d_config! 

On the way through fmgr_oldstyle things go very much awry and the gserialized_spgist_quadtree_2d_config doesn’t get called with a pointer to an fcinfo, but with a pointer to the block of memory occupied by the first argument, and from there things naturally stop working.

So, I’m wondering what I could have done that is causing my calls to route through fmgr_oldstyle instead of the usual path?

P.

--
Paul Ramsey
http://cleverelephant.ca
http://postgis.net

[Andres Freund]

Hi Paul,

Post by Paul Ramsey
I’m trying to implement an spgist index in the PostGIS extension, which seems like it should work, but is thus far not working for what appear (to me) to be issues in the way spgist expects to pass pointers to user-defined functions.
Right before anything happens, spgist calls a ‘config’ routine in the user code. This is the code from the example implementation (which is internal to pgsql, not a run-time add-on like postgis)
 Datum
 spg_quad_config(PG_FUNCTION_ARGS)
 {
 /* spgConfigIn *cfgin = (spgConfigIn *) PG_GETARG_POINTER(0); */
 spgConfigOut *cfg = (spgConfigOut *) PG_GETARG_POINTER(1); 
 cfg->prefixType = POINTOID;
 cfg->labelType = VOIDOID; /* we don't need node labels */
 cfg->canReturnData = true;
 cfg->longValuesOK = false;
 PG_RETURN_VOID();
 }
It is called from the spgist core in the spgGetCache() function, via 
 FunctionCall2Coll(procinfo,
   index->rd_indcollation[0],
   PointerGetDatum(&in),
   PointerGetDatum(&cache->config));
The part the user function cares about is the pointer to cache->config. 
postgres`spg_quad_config(fcinfo=0x00007fff5f0faf90) + 18 at spgquadtreeproc.c:29
postgres`FunctionCall2Coll(flinfo=0x00007ff59a804cc8, collation=0, arg1=140734788252568, arg2=140692835814944) + 150 at fmgr.c:1327
 postgres`spgGetCache(index=0x000000010254be68) + 220 at spgutils.c:71
So, spgGetCache to FunctionCall2Coll to spg_quad_config.
In my user-defined version of the same thing (I just copied the C code and wrote a CREATE OPERATOR CLASS for it) the call stack is this
postgis-2.2.so`gserialized_spgist_quadtree_2d_config(fcinfo=0x00007fff5f0fb398) + 30 at gserialized_spgist_2d.c:60
postgres`fmgr_oldstyle(fcinfo=0x00007fff5f0faf90) + 424 at fmgr.c:678
postgres`FunctionCall2Coll(flinfo=0x00007ff59a039cc8, collation=0, arg1=140734788252568, arg2=140692827643424) + 150 at fmgr.c:1327
postgres`spgGetCache(index=0x000000010254be68) + 220 at spgutils.c:71
So, spgGetCache to FunctionCall2Coll to fmgr_oldstyle to 
gserialized_spgist_quadtree_2d_config! 
On the way through fmgr_oldstyle things go very much awry and the gserialized_spgist_quadtree_2d_config doesn’t get called with a pointer to an fcinfo, but with a pointer to the block of memory occupied by the first argument, and from there things naturally stop working.
So, I’m wondering what I could have done that is causing my calls to route through fmgr_oldstyle instead of the usual path?

You forgot to add a PG_FUNCTION_INFO_V1(yourfunc); for the function.

I really, really think we should get rid of v0 functions. I've seen
errors like this far too many, and they really don't buy us much.

Greetings,

Andres Freund

[Paul Ramsey]

Oh vey, I knew after spending a half-day walking through the debugger it would turn out to be a trivial mistake on my part. This is always how it is when the Magic Fails to Work :) Thanks so much for the help! (and now I know a lot more about the function manager (well, the old one)).

P

-- 
Paul Ramsey
http://cleverelephant.ca
http://postgis.net

On September 23, 2014 at 10:02:33 AM, Andres Freund (***@2ndquadrant.com) wrote:

You forgot to add a PG_FUNCTION_INFO_V1(yourfunc); for the function.