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353 lines
10 KiB
C
353 lines
10 KiB
C
/*-------------------------------------------------------------------------
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*
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* fastpath.c--
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* routines to handle function requests from the frontend
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*
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* Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/tcop/fastpath.c,v 1.2 1996/11/03 06:52:32 scrappy Exp $
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*
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* NOTES
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* This cruft is the server side of PQfn.
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*
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* - jolly 07/11/95:
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*
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* no longer rely on return sizes provided by the frontend. Always
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* use the true lengths for the catalogs. Assume that the frontend
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* has allocated enough space to handle the result value returned.
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*
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* trust that the user knows what he is doing with the args. If the
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* sys catalog says it is a varlena, assume that the user is only sending
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* down VARDATA and that the argsize is the VARSIZE. If the arg is
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* fixed len, assume that the argsize given by the user is correct.
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*
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* if the function returns by value, then only send 4 bytes value
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* back to the frontend. If the return returns by reference,
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* send down only the data portion and set the return size appropriately.
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*
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* OLD COMMENTS FOLLOW
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*
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* The VAR_LENGTH_{ARGS,RESULT} stuff is limited to MAX_STRING_LENGTH
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* (see src/backend/tmp/fastpath.h) for no obvious reason. Since its
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* primary use (for us) is for Inversion path names, it should probably
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* be increased to 256 (MAXPATHLEN for Inversion, hidden in pg_type
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* as well as utils/adt/filename.c).
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*
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* Quoth PMA on 08/15/93:
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*
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* This code has been almost completely rewritten with an eye to
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* keeping it as compatible as possible with the previous (broken)
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* implementation.
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*
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* The previous implementation would assume (1) that any value of
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* length <= 4 bytes was passed-by-value, and that any other value
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* was a struct varlena (by-reference). There was NO way to pass a
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* fixed-length by-reference argument (like char16) or a struct
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* varlena of size <= 4 bytes.
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*
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* The new implementation checks the catalogs to determine whether
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* a value is by-value (type "0" is null-delimited character string,
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* as it is for, e.g., the parser). The only other item obtained
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* from the catalogs is whether or not the value should be placed in
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* a struct varlena or not. Otherwise, the size given by the
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* frontend is assumed to be correct (probably a bad decision, but
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* we do strange things in the name of compatibility).
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "tcop/tcopdebug.h"
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#include "utils/palloc.h"
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#include "fmgr.h"
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#include "utils/builtins.h" /* for oideq */
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#include "tcop/fastpath.h"
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#include "libpq/libpq.h"
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#include "access/xact.h" /* for TransactionId/CommandId protos */
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#include "utils/syscache.h"
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#include "catalog/pg_proc.h"
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#include "catalog/pg_type.h"
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/* ----------------
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* SendFunctionResult
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* ----------------
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*/
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static void
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SendFunctionResult(Oid fid, /* function id */
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char *retval, /* actual return value */
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bool retbyval,
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int retlen /* the length according to the catalogs */
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)
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{
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pq_putnchar("V", 1);
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if (retlen != 0) {
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pq_putnchar("G", 1);
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if (retbyval) { /* by-value */
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pq_putint(retlen, 4);
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pq_putint((int)retval, retlen);
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} else { /* by-reference ... */
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if (retlen < 0) { /* ... varlena */
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pq_putint(VARSIZE(retval) - VARHDRSZ, 4);
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pq_putnchar(VARDATA(retval), VARSIZE(retval) - VARHDRSZ);
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} else { /* ... fixed */
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pq_putint(retlen, 4);
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pq_putnchar(retval, retlen);
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}
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}
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}
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pq_putnchar("0", 1);
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pq_flush();
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}
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/*
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* This structure saves enough state so that one can avoid having to
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* do catalog lookups over and over again. (Each RPC can require up
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* to MAXFMGRARGS+2 lookups, which is quite tedious.)
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*
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* The previous incarnation of this code just assumed that any argument
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* of size <= 4 was by value; this is not correct. There is no cheap
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* way to determine function argument length etc.; one must simply pay
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* the price of catalog lookups.
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*/
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struct fp_info {
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Oid funcid;
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int nargs;
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bool argbyval[MAXFMGRARGS];
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int32 arglen[MAXFMGRARGS]; /* signed (for varlena) */
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bool retbyval;
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int32 retlen; /* signed (for varlena) */
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TransactionId xid;
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CommandId cid;
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};
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/*
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* We implement one-back caching here. If we need to do more, we can.
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* Most routines in tight loops (like PQfswrite -> F_LOWRITE) will do
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* the same thing repeatedly.
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*/
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static struct fp_info last_fp = { InvalidOid };
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/*
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* valid_fp_info
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*
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* RETURNS:
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* 1 if the state in 'fip' is valid
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* 0 otherwise
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*
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* "valid" means:
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* The saved state was either uninitialized, for another function,
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* or from a previous command. (Commands can do updates, which
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* may invalidate catalog entries for subsequent commands. This
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* is overly pessimistic but since there is no smarter invalidation
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* scheme...).
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*/
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static int
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valid_fp_info(Oid func_id, struct fp_info *fip)
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{
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Assert(OidIsValid(func_id));
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Assert(fip != (struct fp_info *) NULL);
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return(OidIsValid(fip->funcid) &&
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oideq(func_id, fip->funcid) &&
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TransactionIdIsCurrentTransactionId(fip->xid) &&
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CommandIdIsCurrentCommandId(fip->cid));
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}
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/*
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* update_fp_info
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*
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* Performs catalog lookups to load a struct fp_info 'fip' for the
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* function 'func_id'.
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*
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* RETURNS:
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* The correct information in 'fip'. Sets 'fip->funcid' to
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* InvalidOid if an exception occurs.
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*/
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static void
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update_fp_info(Oid func_id, struct fp_info *fip)
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{
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Oid *argtypes; /* an oid8 */
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Oid rettype;
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HeapTuple func_htp, type_htp;
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TypeTupleForm tp;
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Form_pg_proc pp;
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int i;
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Assert(OidIsValid(func_id));
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Assert(fip != (struct fp_info *) NULL);
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/*
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* Since the validity of this structure is determined by whether
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* the funcid is OK, we clear the funcid here. It must not be
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* set to the correct value until we are about to return with
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* a good struct fp_info, since we can be interrupted (i.e., with
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* an elog(WARN, ...)) at any time.
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*/
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memset((char *) fip, 0, (int) sizeof(struct fp_info));
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fip->funcid = InvalidOid;
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func_htp = SearchSysCacheTuple(PROOID, ObjectIdGetDatum(func_id),
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0,0,0);
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if (!HeapTupleIsValid(func_htp)) {
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elog(WARN, "update_fp_info: cache lookup for function %d failed",
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func_id);
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}
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pp = (Form_pg_proc) GETSTRUCT(func_htp);
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fip->nargs = pp->pronargs;
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rettype = pp->prorettype;
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argtypes = pp->proargtypes;
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for (i = 0; i < fip->nargs; ++i) {
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if (OidIsValid(argtypes[i])) {
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type_htp = SearchSysCacheTuple(TYPOID,
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ObjectIdGetDatum(argtypes[i]),
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0,0,0);
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if (!HeapTupleIsValid(type_htp)) {
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elog(WARN, "update_fp_info: bad argument type %d for %d",
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argtypes[i], func_id);
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}
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tp = (TypeTupleForm) GETSTRUCT(type_htp);
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fip->argbyval[i] = tp->typbyval;
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fip->arglen[i] = tp->typlen;
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} /* else it had better be VAR_LENGTH_ARG */
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}
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if (OidIsValid(rettype)) {
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type_htp = SearchSysCacheTuple(TYPOID, ObjectIdGetDatum(rettype),
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0,0,0);
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if (!HeapTupleIsValid(type_htp)) {
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elog(WARN, "update_fp_info: bad return type %d for %d",
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rettype, func_id);
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}
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tp = (TypeTupleForm) GETSTRUCT(type_htp);
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fip->retbyval = tp->typbyval;
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fip->retlen = tp->typlen;
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} /* else it had better by VAR_LENGTH_RESULT */
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fip->xid = GetCurrentTransactionId();
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fip->cid = GetCurrentCommandId();
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/*
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* This must be last!
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*/
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fip->funcid = func_id;
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}
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/*
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* HandleFunctionRequest
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*
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* Server side of PQfn (fastpath function calls from the frontend).
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* This corresponds to the libpq protocol symbol "F".
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*
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* RETURNS:
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* nothing of significance.
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* All errors result in elog(WARN,...).
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*/
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int
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HandleFunctionRequest()
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{
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Oid fid;
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int argsize;
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int nargs;
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char *arg[8];
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char *retval;
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int i;
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uint32 palloced;
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char *p;
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struct fp_info *fip;
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fid = (Oid) pq_getint(4); /* function oid */
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nargs = pq_getint(4); /* # of arguments */
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/*
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* This is where the one-back caching is done.
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* If you want to save more state, make this a loop around an array.
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*/
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fip = &last_fp;
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if (!valid_fp_info(fid, fip)) {
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update_fp_info(fid, fip);
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}
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if (fip->nargs != nargs) {
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elog(WARN, "HandleFunctionRequest: actual arguments (%d) != registered arguments (%d)",
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nargs, fip->nargs);
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}
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/*
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* Copy arguments into arg vector. If we palloc() an argument, we need
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* to remember, so that we pfree() it after the call.
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*/
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palloced = 0x0;
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for (i = 0; i < 8; ++i) {
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if (i >= nargs) {
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arg[i] = (char *) NULL;
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} else {
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argsize = pq_getint(4);
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Assert(argsize > 0);
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if (fip->argbyval[i]) { /* by-value */
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Assert(argsize <= 4);
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arg[i] = (char *) pq_getint(argsize);
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} else { /* by-reference ... */
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if (fip->arglen[i] < 0) { /* ... varlena */
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if (!(p = palloc(argsize + VARHDRSZ))) {
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elog(WARN, "HandleFunctionRequest: palloc failed");
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}
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VARSIZE(p) = argsize + VARHDRSZ;
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pq_getnchar(VARDATA(p), 0, argsize);
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} else { /* ... fixed */
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/* XXX cross our fingers and trust "argsize" */
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if (!(p = palloc(argsize))) {
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elog(WARN, "HandleFunctionRequest: palloc failed");
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}
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pq_getnchar(p, 0, argsize);
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}
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palloced |= (1 << i);
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arg[i] = p;
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}
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}
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}
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#ifndef NO_FASTPATH
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retval = fmgr(fid,
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arg[0], arg[1], arg[2], arg[3],
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arg[4], arg[5], arg[6], arg[7]);
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#else
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retval = NULL;
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#endif /* NO_FASTPATH */
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/* free palloc'ed arguments */
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for (i = 0; i < nargs; ++i) {
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if (palloced & (1 << i))
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pfree(arg[i]);
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}
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/*
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* If this is an ordinary query (not a retrieve portal p ...), then
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* we return the data to the user. If the return value was palloc'ed,
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* then it must also be freed.
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*/
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#ifndef NO_FASTPATH
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SendFunctionResult(fid, retval, fip->retbyval, fip->retlen);
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#else
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SendFunctionResult(fid, retval, fip->retbyval, 0);
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#endif /* NO_FASTPATH */
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if (!fip->retbyval)
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pfree(retval);
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return(0);
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}
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