/*-------------------------------------------------------------------------
*
* fastpath.c
* routines to handle function requests from the frontend
*
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/tcop/fastpath.c,v 1.49 2001/06/01 15:45:42 tgl Exp $
*
* NOTES
* This cruft is the server side of PQfn.
*
* - jolly 07/11/95:
*
* no longer rely on return sizes provided by the frontend. Always
* use the true lengths for the catalogs. Assume that the frontend
* has allocated enough space to handle the result value returned.
*
* trust that the user knows what he is doing with the args. If the
* sys catalog says it is a varlena, assume that the user is only sending
* down VARDATA and that the argsize is the VARSIZE. If the arg is
* fixed len, assume that the argsize given by the user is correct.
*
* if the function returns by value, then only send 4 bytes value
* back to the frontend. If the return returns by reference,
* send down only the data portion and set the return size appropriately.
*
* OLD COMMENTS FOLLOW
*
* The VAR_LENGTH_{ARGS,RESULT} stuff is limited to MAX_STRING_LENGTH
* (see src/backend/tmp/fastpath.h) for no obvious reason. Since its
* primary use (for us) is for Inversion path names, it should probably
* be increased to 256 (MAXPATHLEN for Inversion, hidden in pg_type
* as well as utils/adt/filename.c).
*
* Quoth PMA on 08/15/93:
*
* This code has been almost completely rewritten with an eye to
* keeping it as compatible as possible with the previous (broken)
* implementation.
*
* The previous implementation would assume (1) that any value of
* length <= 4 bytes was passed-by-value, and that any other value
* was a struct varlena (by-reference). There was NO way to pass a
* fixed-length by-reference argument (like name) or a struct
* varlena of size <= 4 bytes.
*
* The new implementation checks the catalogs to determine whether
* a value is by-value (type "0" is null-delimited character string,
* as it is for, e.g., the parser). The only other item obtained
* from the catalogs is whether or not the value should be placed in
* a struct varlena or not. Otherwise, the size given by the
* frontend is assumed to be correct (probably a bad decision, but
* we do strange things in the name of compatibility).
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/xact.h"
#include "catalog/pg_proc.h"
#include "libpq/libpq.h"
#include "libpq/pqformat.h"
#include "tcop/fastpath.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
/* ----------------
* SendFunctionResult
* ----------------
*/
static void
SendFunctionResult(Datum retval,/* actual return value */
bool retbyval,
int retlen) /* the length according to the catalogs */
{
StringInfoData buf;
pq_beginmessage(&buf);
pq_sendbyte(&buf, 'V');
if (retlen != 0)
{
pq_sendbyte(&buf, 'G');
if (retbyval)
{ /* by-value */
pq_sendint(&buf, retlen, 4);
pq_sendint(&buf, DatumGetInt32(retval), retlen);
}
else
{ /* by-reference ... */
if (retlen < 0)
{ /* ... varlena */
struct varlena *v = (struct varlena *) DatumGetPointer(retval);
pq_sendint(&buf, VARSIZE(v) - VARHDRSZ, VARHDRSZ);
pq_sendbytes(&buf, VARDATA(v), VARSIZE(v) - VARHDRSZ);
}
else
{ /* ... fixed */
pq_sendint(&buf, retlen, 4);
pq_sendbytes(&buf, DatumGetPointer(retval), retlen);
}
}
}
pq_sendbyte(&buf, '0');
pq_endmessage(&buf);
}
/*
* Formerly, this code attempted to cache the function and type info
* looked up by fetch_fp_info, but only for the duration of a single
* transaction command (since in theory the info could change between
* commands). This was utterly useless, because postgres.c executes
* each fastpath call as a separate transaction command, and so the
* cached data could never actually have been reused. If it had worked
* as intended, it would have had problems anyway with dangling references
* in the FmgrInfo struct. So, forget about caching and just repeat the
* syscache fetches on each usage. They're not *that* expensive.
*/
struct fp_info
{
Oid funcid;
FmgrInfo flinfo; /* function lookup info for funcid */
int16 arglen[FUNC_MAX_ARGS];
bool argbyval[FUNC_MAX_ARGS];
int16 retlen;
bool retbyval;
};
/*
* fetch_fp_info
*
* Performs catalog lookups to load a struct fp_info 'fip' for the
* function 'func_id'.
*/
static void
fetch_fp_info(Oid func_id, struct fp_info * fip)
{
Oid *argtypes; /* an oidvector */
Oid rettype;
HeapTuple func_htp;
Form_pg_proc pp;
int i;
Assert(OidIsValid(func_id));
Assert(fip != (struct fp_info *) NULL);
/*
* Since the validity of this structure is determined by whether the
* funcid is OK, we clear the funcid here. It must not be set to the
* correct value until we are about to return with a good struct
* fp_info, since we can be interrupted (i.e., with an elog(ERROR,
* ...)) at any time. [No longer really an issue since we don't save
* the struct fp_info across transactions anymore, but keep it anyway.]
*/
MemSet((char *) fip, 0, sizeof(struct fp_info));
fip->funcid = InvalidOid;
fmgr_info(func_id, &fip->flinfo);
func_htp = SearchSysCache(PROCOID,
ObjectIdGetDatum(func_id),
0, 0, 0);
if (!HeapTupleIsValid(func_htp))
elog(ERROR, "fetch_fp_info: cache lookup for function %u failed",
func_id);
pp = (Form_pg_proc) GETSTRUCT(func_htp);
rettype = pp->prorettype;
argtypes = pp->proargtypes;
for (i = 0; i < pp->pronargs; ++i)
{
if (OidIsValid(argtypes[i]))
get_typlenbyval(argtypes[i], &fip->arglen[i], &fip->argbyval[i]);
}
if (OidIsValid(rettype))
get_typlenbyval(rettype, &fip->retlen, &fip->retbyval);
ReleaseSysCache(func_htp);
/*
* This must be last!
*/
fip->funcid = func_id;
}
/*
* HandleFunctionRequest
*
* Server side of PQfn (fastpath function calls from the frontend).
* This corresponds to the libpq protocol symbol "F".
*
* RETURNS:
* 0 if successful completion, EOF if frontend connection lost.
*
* Note: All ordinary errors result in elog(ERROR,...). However,
* if we lose the frontend connection there is no one to elog to,
* and no use in proceeding...
*
* Note: palloc()s done here and in the called function do not need to be
* cleaned up explicitly. We are called from PostgresMain() in the
* QueryContext memory context, which will be automatically reset when
* control returns to PostgresMain.
*/
int
HandleFunctionRequest(void)
{
Oid fid;
int argsize;
int nargs;
int tmp;
FunctionCallInfoData fcinfo;
Datum retval;
int i;
char *p;
struct fp_info my_fp;
struct fp_info *fip;
/*
* XXX FIXME: This protocol is misdesigned.
*
* We really do not want to elog() before having swallowed all of the
* frontend's fastpath message; otherwise we will lose sync with the
* input datastream. What should happen is we absorb all of the input
* message per protocol syntax, and *then* do error checking
* (including lookup of the given function ID) and elog if
* appropriate. Unfortunately, because we cannot even read the
* message properly without knowing whether the data types are
* pass-by-ref or pass-by-value, it's not all that easy to do :-(. The
* protocol should require the client to supply what it thinks is the
* typbyval and typlen value for each arg, so that we can read the
* data without having to do any lookups. Then after we've read the
* message, we should do the lookups, verify agreement of the actual
* function arg types with what we received, and finally call the
* function.
*
* As things stand, not only will we lose sync for an invalid message
* (such as requested function OID doesn't exist), but we may lose
* sync for a perfectly valid message if we are in transaction-aborted
* state! This can happen because our database lookup attempts may
* fail entirely in abort state.
*
* Unfortunately I see no way to fix this without breaking a lot of
* existing clients. Maybe do it as part of next protocol version
* change.
*/
if (pq_getint(&tmp, 4)) /* function oid */
return EOF;
fid = (Oid) tmp;
if (pq_getint(&nargs, 4)) /* # of arguments */
return EOF;
/*
* There used to be a lame attempt at caching lookup info here.
* Now we just do the lookups on every call.
*/
fip = &my_fp;
fetch_fp_info(fid, fip);
if (fip->flinfo.fn_nargs != nargs || nargs > FUNC_MAX_ARGS)
{
elog(ERROR, "HandleFunctionRequest: actual arguments (%d) != registered arguments (%d)",
nargs, fip->flinfo.fn_nargs);
}
MemSet(&fcinfo, 0, sizeof(fcinfo));
fcinfo.flinfo = &fip->flinfo;
fcinfo.nargs = nargs;
/*
* Copy supplied arguments into arg vector. Note there is no way for
* frontend to specify a NULL argument --- more misdesign.
*/
for (i = 0; i < nargs; ++i)
{
if (pq_getint(&argsize, 4))
return EOF;
if (fip->argbyval[i])
{ /* by-value */
if (argsize < 1 || argsize > 4)
elog(ERROR, "HandleFunctionRequest: bogus argsize %d",
argsize);
/* XXX should we demand argsize == fip->arglen[i] ? */
if (pq_getint(&tmp, argsize))
return EOF;
fcinfo.arg[i] = (Datum) tmp;
}
else
{ /* by-reference ... */
if (fip->arglen[i] < 0)
{ /* ... varlena */
if (argsize < 0)
elog(ERROR, "HandleFunctionRequest: bogus argsize %d",
argsize);
/* I suspect this +1 isn't really needed - tgl 5/2000 */
p = palloc(argsize + VARHDRSZ + 1); /* Added +1 to solve
* memory leak - Peter
* 98 Jan 6 */
VARATT_SIZEP(p) = argsize + VARHDRSZ;
if (pq_getbytes(VARDATA(p), argsize))
return EOF;
}
else
{ /* ... fixed */
if (argsize != fip->arglen[i])
elog(ERROR, "HandleFunctionRequest: bogus argsize %d, should be %d",
argsize, fip->arglen[i]);
p = palloc(argsize + 1); /* +1 in case argsize is 0 */
if (pq_getbytes(p, argsize))
return EOF;
}
fcinfo.arg[i] = PointerGetDatum(p);
}
}
/*
* Now that we've eaten the input message, check to see if we actually
* want to do the function call or not.
*
* Currently, we report an error if in ABORT state, or return a dummy
* NULL response if fastpath support has been compiled out.
*/
if (IsAbortedTransactionBlockState())
elog(ERROR, "current transaction is aborted, "
"queries ignored until end of transaction block");
#ifdef NO_FASTPATH
/* force a NULL return */
retval = (Datum) 0;
fcinfo.isnull = true;
#else
retval = FunctionCallInvoke(&fcinfo);
#endif /* NO_FASTPATH */
if (fcinfo.isnull)
SendFunctionResult(retval, fip->retbyval, 0);
else
SendFunctionResult(retval, fip->retbyval, fip->retlen);
return 0;
}