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414 lines
12 KiB
C
414 lines
12 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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* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
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* Portions 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 1.46 2001/01/24 19:43:09 momjian 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 name) 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 "access/xact.h"
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#include "catalog/pg_proc.h"
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#include "catalog/pg_type.h"
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#include "libpq/libpq.h"
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#include "libpq/pqformat.h"
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#include "tcop/fastpath.h"
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#include "utils/syscache.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(Datum 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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StringInfoData buf;
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pq_beginmessage(&buf);
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pq_sendbyte(&buf, 'V');
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if (retlen != 0)
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{
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pq_sendbyte(&buf, 'G');
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if (retbyval)
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{ /* by-value */
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pq_sendint(&buf, retlen, 4);
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pq_sendint(&buf, DatumGetInt32(retval), retlen);
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}
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else
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{ /* by-reference ... */
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if (retlen < 0)
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{ /* ... varlena */
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struct varlena *v = (struct varlena *) DatumGetPointer(retval);
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pq_sendint(&buf, VARSIZE(v) - VARHDRSZ, VARHDRSZ);
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pq_sendbytes(&buf, VARDATA(v), VARSIZE(v) - VARHDRSZ);
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}
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else
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{ /* ... fixed */
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pq_sendint(&buf, retlen, 4);
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pq_sendbytes(&buf, DatumGetPointer(retval), retlen);
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}
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}
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}
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pq_sendbyte(&buf, '0');
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pq_endmessage(&buf);
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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 FUNC_MAX_ARGS+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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{
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Oid funcid;
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FmgrInfo flinfo; /* function lookup info for funcid */
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bool argbyval[FUNC_MAX_ARGS];
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int32 arglen[FUNC_MAX_ARGS]; /* signed (for varlena) */
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bool retbyval;
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int32 retlen; /* signed (for varlena) */
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TransactionId xid; /* when the lookup was done */
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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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* T if the state in 'fip' is valid for the given func OID
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* F otherwise
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*
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* "invalid" 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 bool
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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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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 oidvector */
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Oid rettype;
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HeapTuple func_htp,
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type_htp;
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Form_pg_type 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 the
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* funcid is OK, we clear the funcid here. It must not be set to the
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* correct value until we are about to return with a good struct
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* fp_info, since we can be interrupted (i.e., with an elog(ERROR,
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* ...)) 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 = SearchSysCache(PROCOID,
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ObjectIdGetDatum(func_id),
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0, 0, 0);
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if (!HeapTupleIsValid(func_htp))
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elog(ERROR, "update_fp_info: cache lookup for function %u failed",
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func_id);
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pp = (Form_pg_proc) GETSTRUCT(func_htp);
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rettype = pp->prorettype;
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argtypes = pp->proargtypes;
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fmgr_info(func_id, &fip->flinfo);
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for (i = 0; i < fip->flinfo.fn_nargs; ++i)
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{
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if (OidIsValid(argtypes[i]))
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{
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type_htp = SearchSysCache(TYPEOID,
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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(ERROR, "update_fp_info: bad argument type %u for %u",
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argtypes[i], func_id);
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tp = (Form_pg_type) 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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ReleaseSysCache(type_htp);
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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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{
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type_htp = SearchSysCache(TYPEOID,
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ObjectIdGetDatum(rettype),
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0, 0, 0);
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if (!HeapTupleIsValid(type_htp))
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elog(ERROR, "update_fp_info: bad return type %u for %u",
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rettype, func_id);
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tp = (Form_pg_type) GETSTRUCT(type_htp);
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fip->retbyval = tp->typbyval;
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fip->retlen = tp->typlen;
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ReleaseSysCache(type_htp);
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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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ReleaseSysCache(func_htp);
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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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* 0 if successful completion, EOF if frontend connection lost.
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*
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* Note: All ordinary errors result in elog(ERROR,...). However,
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* if we lose the frontend connection there is no one to elog to,
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* and no use in proceeding...
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*
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* Note: palloc()s done here and in the called function do not need to be
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* cleaned up explicitly. We are called from PostgresMain() in the
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* QueryContext memory context, which will be automatically reset when
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* control returns to PostgresMain.
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*/
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int
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HandleFunctionRequest(void)
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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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int tmp;
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FunctionCallInfoData fcinfo;
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Datum retval;
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int i;
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char *p;
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struct fp_info *fip;
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/*
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* XXX FIXME: This protocol is misdesigned.
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*
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* We really do not want to elog() before having swallowed all of the
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* frontend's fastpath message; otherwise we will lose sync with the input
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* datastream. What should happen is we absorb all of the input message
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* per protocol syntax, and *then* do error checking (including lookup of
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* the given function ID) and elog if appropriate. Unfortunately, because
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* we cannot even read the message properly without knowing whether the
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* data types are pass-by-ref or pass-by-value, it's not all that easy to
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* do :-(. The protocol should require the client to supply what it
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* thinks is the typbyval and typlen value for each arg, so that we can
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* read the data without having to do any lookups. Then after we've read
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* the message, we should do the lookups, verify agreement of the actual
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* function arg types with what we received, and finally call the function.
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*
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* As things stand, not only will we lose sync for an invalid message
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* (such as requested function OID doesn't exist), but we may lose sync
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* for a perfectly valid message if we are in transaction-aborted state!
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* This can happen because our database lookup attempts may fail entirely
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* in abort state.
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*
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* Unfortunately I see no way to fix this without breaking a lot of
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* existing clients. Maybe do it as part of next protocol version change.
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*/
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if (pq_getint(&tmp, 4)) /* function oid */
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return EOF;
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fid = (Oid) tmp;
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if (pq_getint(&nargs, 4)) /* # of arguments */
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return EOF;
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/*
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* This is where the one-back caching is done. If you want to save
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* more state, make this a loop around an array. Given the relatively
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* short lifespan of the cache, not clear that there's any win possible.
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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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if (fip->flinfo.fn_nargs != nargs || nargs > FUNC_MAX_ARGS)
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{
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elog(ERROR, "HandleFunctionRequest: actual arguments (%d) != registered arguments (%d)",
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nargs, fip->flinfo.fn_nargs);
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}
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MemSet(&fcinfo, 0, sizeof(fcinfo));
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fcinfo.flinfo = &fip->flinfo;
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fcinfo.nargs = nargs;
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/*
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* Copy supplied arguments into arg vector. Note there is no way for
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* frontend to specify a NULL argument --- more misdesign.
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*/
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for (i = 0; i < nargs; ++i)
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{
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if (pq_getint(&argsize, 4))
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return EOF;
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if (fip->argbyval[i])
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{ /* by-value */
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if (argsize < 1 || argsize > 4)
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elog(ERROR, "HandleFunctionRequest: bogus argsize %d",
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argsize);
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/* XXX should we demand argsize == fip->arglen[i] ? */
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if (pq_getint(&tmp, argsize))
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return EOF;
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fcinfo.arg[i] = (Datum) tmp;
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}
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else
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{ /* by-reference ... */
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if (fip->arglen[i] < 0)
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{ /* ... varlena */
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if (argsize < 0)
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elog(ERROR, "HandleFunctionRequest: bogus argsize %d",
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argsize);
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/* I suspect this +1 isn't really needed - tgl 5/2000 */
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p = palloc(argsize + VARHDRSZ + 1); /* Added +1 to solve
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* memory leak - Peter
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* 98 Jan 6 */
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VARATT_SIZEP(p) = argsize + VARHDRSZ;
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if (pq_getbytes(VARDATA(p), argsize))
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return EOF;
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}
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else
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{ /* ... fixed */
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if (argsize != fip->arglen[i])
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elog(ERROR, "HandleFunctionRequest: bogus argsize %d, should be %d",
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argsize, fip->arglen[i]);
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p = palloc(argsize + 1); /* +1 in case argsize is 0 */
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if (pq_getbytes(p, argsize))
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return EOF;
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}
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fcinfo.arg[i] = PointerGetDatum(p);
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}
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}
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/*
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* Now that we've eaten the input message, check to see if we actually
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* want to do the function call or not.
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*
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* Currently, we report an error if in ABORT state, or return a dummy
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* NULL response if fastpath support has been compiled out.
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*/
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if (IsAbortedTransactionBlockState())
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elog(ERROR, "current transaction is aborted, "
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"queries ignored until end of transaction block");
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#ifdef NO_FASTPATH
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/* force a NULL return */
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retval = (Datum) 0;
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fcinfo.isnull = true;
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#else
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retval = FunctionCallInvoke(&fcinfo);
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#endif /* NO_FASTPATH */
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if (fcinfo.isnull)
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SendFunctionResult(retval, fip->retbyval, 0);
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else
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SendFunctionResult(retval, fip->retbyval, fip->retlen);
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return 0;
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}
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