fmgr.c

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/*-------------------------------------------------------------------------
 *
 * fmgr.c
 *	  The Postgres function manager.
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.113 2008/01/03 21:23:15 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/heapam.h"
#include "access/tuptoaster.h"
#include "catalog/pg_language.h"
#include "catalog/pg_proc.h"
#include "executor/functions.h"
#include "miscadmin.h"
#include "parser/parse_expr.h"
#include "utils/builtins.h"
#include "utils/fmgrtab.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"


/*
 * Declaration for old-style function pointer type.  This is now used only
 * in fmgr_oldstyle() and is no longer exported.
 *
 * The m68k SVR4 ABI defines that pointers are returned in %a0 instead of
 * %d0. So if a function pointer is declared to return a pointer, the
 * compiler may look only into %a0, but if the called function was declared
 * to return an integer type, it puts its value only into %d0. So the
 * caller doesn't pick up the correct return value. The solution is to
 * declare the function pointer to return int, so the compiler picks up the
 * return value from %d0. (Functions returning pointers put their value
 * *additionally* into %d0 for compatibility.) The price is that there are
 * some warnings about int->pointer conversions ... which we can suppress
 * with suitably ugly casts in fmgr_oldstyle().
 */
#if (defined(__mc68000__) || (defined(__m68k__))) && defined(__ELF__)
typedef int32 (*func_ptr) ();
#else
typedef char *(*func_ptr) ();
#endif

/*
 * For an oldstyle function, fn_extra points to a record like this:
 */
typedef struct
{
	func_ptr	func;			/* Address of the oldstyle function */
	bool		arg_toastable[FUNC_MAX_ARGS];	/* is n'th arg of a toastable
												 * datatype? */
} Oldstyle_fnextra;

/*
 * Hashtable for fast lookup of external C functions
 */
typedef struct
{
	/* fn_oid is the hash key and so must be first! */
	Oid			fn_oid;			/* OID of an external C function */
	TransactionId fn_xmin;		/* for checking up-to-dateness */
	ItemPointerData fn_tid;
	PGFunction	user_fn;		/* the function's address */
	const Pg_finfo_record *inforec;		/* address of its info record */
} CFuncHashTabEntry;

static HTAB *CFuncHash = NULL;


static void fmgr_info_cxt_security(Oid functionId, FmgrInfo *finfo, MemoryContext mcxt,
					   bool ignore_security);
static void fmgr_info_C_lang(Oid functionId, FmgrInfo *finfo, HeapTuple procedureTuple);
static void fmgr_info_other_lang(Oid functionId, FmgrInfo *finfo, HeapTuple procedureTuple);
static CFuncHashTabEntry *lookup_C_func(HeapTuple procedureTuple);
static void record_C_func(HeapTuple procedureTuple,
			  PGFunction user_fn, const Pg_finfo_record *inforec);
static Datum fmgr_oldstyle(PG_FUNCTION_ARGS);
static Datum fmgr_security_definer(PG_FUNCTION_ARGS);


/*
 * Lookup routines for builtin-function table.	We can search by either Oid
 * or name, but search by Oid is much faster.
 */

static const FmgrBuiltin *
fmgr_isbuiltin(Oid id)
{
	int			low = 0;
	int			high = fmgr_nbuiltins - 1;

	/*
	 * Loop invariant: low is the first index that could contain target entry,
	 * and high is the last index that could contain it.
	 */
	while (low <= high)
	{
		int			i = (high + low) / 2;
		const FmgrBuiltin *ptr = &fmgr_builtins[i];

		if (id == ptr->foid)
			return ptr;
		else if (id > ptr->foid)
			low = i + 1;
		else
			high = i - 1;
	}
	return NULL;
}

/*
 * Lookup a builtin by name.  Note there can be more than one entry in
 * the array with the same name, but they should all point to the same
 * routine.
 */
static const FmgrBuiltin *
fmgr_lookupByName(const char *name)
{
	int			i;

	for (i = 0; i < fmgr_nbuiltins; i++)
	{
		if (strcmp(name, fmgr_builtins[i].funcName) == 0)
			return fmgr_builtins + i;
	}
	return NULL;
}

/*
 * This routine fills a FmgrInfo struct, given the OID
 * of the function to be called.
 *
 * The caller's CurrentMemoryContext is used as the fn_mcxt of the info
 * struct; this means that any subsidiary data attached to the info struct
 * (either by fmgr_info itself, or later on by a function call handler)
 * will be allocated in that context.  The caller must ensure that this
 * context is at least as long-lived as the info struct itself.  This is
 * not a problem in typical cases where the info struct is on the stack or
 * in freshly-palloc'd space.  However, if one intends to store an info
 * struct in a long-lived table, it's better to use fmgr_info_cxt.
 */
void
fmgr_info(Oid functionId, FmgrInfo *finfo)
{
	fmgr_info_cxt(functionId, finfo, CurrentMemoryContext);
}

/*
 * Fill a FmgrInfo struct, specifying a memory context in which its
 * subsidiary data should go.
 */
void
fmgr_info_cxt(Oid functionId, FmgrInfo *finfo, MemoryContext mcxt)
{
	fmgr_info_cxt_security(functionId, finfo, mcxt, false);
}

/*
 * This one does the actual work.  ignore_security is ordinarily false
 * but is set to true by fmgr_security_definer to avoid infinite
 * recursive lookups.
 */
static void
fmgr_info_cxt_security(Oid functionId, FmgrInfo *finfo, MemoryContext mcxt,
					   bool ignore_security)
{
	const FmgrBuiltin *fbp;
	HeapTuple	procedureTuple;
	Form_pg_proc procedureStruct;
	Datum		prosrcdatum;
	bool		isnull;
	char	   *prosrc;

	/*
	 * fn_oid *must* be filled in last.  Some code assumes that if fn_oid is
	 * valid, the whole struct is valid.  Some FmgrInfo struct's do survive
	 * elogs.
	 */
	finfo->fn_oid = InvalidOid;
	finfo->fn_extra = NULL;
	finfo->fn_mcxt = mcxt;
	finfo->fn_expr = NULL;		/* caller may set this later */

	if ((fbp = fmgr_isbuiltin(functionId)) != NULL)
	{
		/*
		 * Fast path for builtin functions: don't bother consulting pg_proc
		 */
		finfo->fn_nargs = fbp->nargs;
		finfo->fn_strict = fbp->strict;
		finfo->fn_retset = fbp->retset;
		finfo->fn_addr = fbp->func;
		finfo->fn_oid = functionId;
		return;
	}

	/* Otherwise we need the pg_proc entry */
	procedureTuple = SearchSysCache(PROCOID,
									ObjectIdGetDatum(functionId),
									0, 0, 0);
	if (!HeapTupleIsValid(procedureTuple))
		elog(ERROR, "cache lookup failed for function %u", functionId);
	procedureStruct = (Form_pg_proc) GETSTRUCT(procedureTuple);

	finfo->fn_nargs = procedureStruct->pronargs;
	finfo->fn_strict = procedureStruct->proisstrict;
	finfo->fn_retset = procedureStruct->proretset;

	/*
	 * If it has prosecdef set, or non-null proconfig, use
	 * fmgr_security_definer call handler.
	 */
	if (!ignore_security &&
		(procedureStruct->prosecdef ||
		 !heap_attisnull(procedureTuple, Anum_pg_proc_proconfig)))
	{
		finfo->fn_addr = fmgr_security_definer;
		finfo->fn_oid = functionId;
		ReleaseSysCache(procedureTuple);
		return;
	}

	switch (procedureStruct->prolang)
	{
		case INTERNALlanguageId:

			/*
			 * For an ordinary builtin function, we should never get here
			 * because the isbuiltin() search above will have succeeded.
			 * However, if the user has done a CREATE FUNCTION to create an
			 * alias for a builtin function, we can end up here.  In that case
			 * we have to look up the function by name.  The name of the
			 * internal function is stored in prosrc (it doesn't have to be
			 * the same as the name of the alias!)
			 */
			prosrcdatum = SysCacheGetAttr(PROCOID, procedureTuple,
										  Anum_pg_proc_prosrc, &isnull);
			if (isnull)
				elog(ERROR, "null prosrc");
			prosrc = DatumGetCString(DirectFunctionCall1(textout,
														 prosrcdatum));
			fbp = fmgr_lookupByName(prosrc);
			if (fbp == NULL)
				ereport(ERROR,
						(errcode(ERRCODE_UNDEFINED_FUNCTION),
						 errmsg("internal function \"%s\" is not in internal lookup table",
								prosrc)));
			pfree(prosrc);
			/* Should we check that nargs, strict, retset match the table? */
			finfo->fn_addr = fbp->func;
			break;

		case ClanguageId:
			fmgr_info_C_lang(functionId, finfo, procedureTuple);
			break;

		case SQLlanguageId:
			finfo->fn_addr = fmgr_sql;
			break;

		default:
			fmgr_info_other_lang(functionId, finfo, procedureTuple);
			break;
	}

	finfo->fn_oid = functionId;
	ReleaseSysCache(procedureTuple);
}

/*
 * Special fmgr_info processing for C-language functions.  Note that
 * finfo->fn_oid is not valid yet.
 */
static void
fmgr_info_C_lang(Oid functionId, FmgrInfo *finfo, HeapTuple procedureTuple)
{
	Form_pg_proc procedureStruct = (Form_pg_proc) GETSTRUCT(procedureTuple);
	CFuncHashTabEntry *hashentry;
	PGFunction	user_fn;
	const Pg_finfo_record *inforec;
	Oldstyle_fnextra *fnextra;
	bool		isnull;
	int			i;

	/*
	 * See if we have the function address cached already
	 */
	hashentry = lookup_C_func(procedureTuple);
	if (hashentry)
	{
		user_fn = hashentry->user_fn;
		inforec = hashentry->inforec;
	}
	else
	{
		Datum		prosrcattr,
					probinattr;
		char	   *prosrcstring,
				   *probinstring;
		void	   *libraryhandle;

		/*
		 * Get prosrc and probin strings (link symbol and library filename)
		 */
		prosrcattr = SysCacheGetAttr(PROCOID, procedureTuple,
									 Anum_pg_proc_prosrc, &isnull);
		if (isnull)
			elog(ERROR, "null prosrc for function %u", functionId);
		prosrcstring = DatumGetCString(DirectFunctionCall1(textout,
														   prosrcattr));

		probinattr = SysCacheGetAttr(PROCOID, procedureTuple,
									 Anum_pg_proc_probin, &isnull);
		if (isnull)
			elog(ERROR, "null probin for function %u", functionId);
		probinstring = DatumGetCString(DirectFunctionCall1(textout,
														   probinattr));

		/* Look up the function itself */
		user_fn = load_external_function(probinstring, prosrcstring, true,
										 &libraryhandle);

		/* Get the function information record (real or default) */
		inforec = fetch_finfo_record(libraryhandle, prosrcstring);

		/* Cache the addresses for later calls */
		record_C_func(procedureTuple, user_fn, inforec);

		pfree(prosrcstring);
		pfree(probinstring);
	}

	switch (inforec->api_version)
	{
		case 0:
			/* Old style: need to use a handler */
			finfo->fn_addr = fmgr_oldstyle;
			fnextra = (Oldstyle_fnextra *)
				MemoryContextAllocZero(finfo->fn_mcxt,
									   sizeof(Oldstyle_fnextra));
			finfo->fn_extra = (void *) fnextra;
			fnextra->func = (func_ptr) user_fn;
			for (i = 0; i < procedureStruct->pronargs; i++)
			{
				fnextra->arg_toastable[i] =
					TypeIsToastable(procedureStruct->proargtypes.values[i]);
			}
			break;
		case 1:
			/* New style: call directly */
			finfo->fn_addr = user_fn;
			break;
		default:
			/* Shouldn't get here if fetch_finfo_record did its job */
			elog(ERROR, "unrecognized function API version: %d",
				 inforec->api_version);
			break;
	}
}

/*
 * Special fmgr_info processing for other-language functions.  Note
 * that finfo->fn_oid is not valid yet.
 */
static void
fmgr_info_other_lang(Oid functionId, FmgrInfo *finfo, HeapTuple procedureTuple)
{
	Form_pg_proc procedureStruct = (Form_pg_proc) GETSTRUCT(procedureTuple);
	Oid			language = procedureStruct->prolang;
	HeapTuple	languageTuple;
	Form_pg_language languageStruct;
	FmgrInfo	plfinfo;

	languageTuple = SearchSysCache(LANGOID,
								   ObjectIdGetDatum(language),
								   0, 0, 0);
	if (!HeapTupleIsValid(languageTuple))
		elog(ERROR, "cache lookup failed for language %u", language);
	languageStruct = (Form_pg_language) GETSTRUCT(languageTuple);

	fmgr_info(languageStruct->lanplcallfoid, &plfinfo);
	finfo->fn_addr = plfinfo.fn_addr;

	/*
	 * If lookup of the PL handler function produced nonnull fn_extra,
	 * complain --- it must be an oldstyle function! We no longer support
	 * oldstyle PL handlers.
	 */
	if (plfinfo.fn_extra != NULL)
		elog(ERROR, "language %u has old-style handler", language);

	ReleaseSysCache(languageTuple);
}

/*
 * Fetch and validate the information record for the given external function.
 * The function is specified by a handle for the containing library
 * (obtained from load_external_function) as well as the function name.
 *
 * If no info function exists for the given name, it is not an error.
 * Instead we return a default info record for a version-0 function.
 * We want to raise an error here only if the info function returns
 * something bogus.
 *
 * This function is broken out of fmgr_info_C_lang so that fmgr_c_validator
 * can validate the information record for a function not yet entered into
 * pg_proc.
 */
const Pg_finfo_record *
fetch_finfo_record(void *filehandle, char *funcname)
{
	char	   *infofuncname;
	PGFInfoFunction infofunc;
	const Pg_finfo_record *inforec;
	static Pg_finfo_record default_inforec = {0};

	/* Compute name of info func */
	infofuncname = (char *) palloc(strlen(funcname) + 10);
	strcpy(infofuncname, "pg_finfo_");
	strcat(infofuncname, funcname);

	/* Try to look up the info function */
	infofunc = (PGFInfoFunction) lookup_external_function(filehandle,
														  infofuncname);
	if (infofunc == NULL)
	{
		/* Not found --- assume version 0 */
		pfree(infofuncname);
		return &default_inforec;
	}

	/* Found, so call it */
	inforec = (*infofunc) ();

	/* Validate result as best we can */
	if (inforec == NULL)
		elog(ERROR, "null result from info function \"%s\"", infofuncname);
	switch (inforec->api_version)
	{
		case 0:
		case 1:
			/* OK, no additional fields to validate */
			break;
		default:
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
					 errmsg("unrecognized API version %d reported by info function \"%s\"",
							inforec->api_version, infofuncname)));
			break;
	}

	pfree(infofuncname);
	return inforec;
}


/*-------------------------------------------------------------------------
 *		Routines for caching lookup information for external C functions.
 *
 * The routines in dfmgr.c are relatively slow, so we try to avoid running
 * them more than once per external function per session.  We use a hash table
 * with the function OID as the lookup key.
 *-------------------------------------------------------------------------
 */

/*
 * lookup_C_func: try to find a C function in the hash table
 *
 * If an entry exists and is up to date, return it; else return NULL
 */
static CFuncHashTabEntry *
lookup_C_func(HeapTuple procedureTuple)
{
	Oid			fn_oid = HeapTupleGetOid(procedureTuple);
	CFuncHashTabEntry *entry;

	if (CFuncHash == NULL)
		return NULL;			/* no table yet */
	entry = (CFuncHashTabEntry *)
		hash_search(CFuncHash,
					&fn_oid,
					HASH_FIND,
					NULL);
	if (entry == NULL)
		return NULL;			/* no such entry */
	if (entry->fn_xmin == HeapTupleHeaderGetXmin(procedureTuple->t_data) &&
		ItemPointerEquals(&entry->fn_tid, &procedureTuple->t_self))
		return entry;			/* OK */
	return NULL;				/* entry is out of date */
}

/*
 * record_C_func: enter (or update) info about a C function in the hash table
 */
static void
record_C_func(HeapTuple procedureTuple,
			  PGFunction user_fn, const Pg_finfo_record *inforec)
{
	Oid			fn_oid = HeapTupleGetOid(procedureTuple);
	CFuncHashTabEntry *entry;
	bool		found;

	/* Create the hash table if it doesn't exist yet */
	if (CFuncHash == NULL)
	{
		HASHCTL		hash_ctl;

		MemSet(&hash_ctl, 0, sizeof(hash_ctl));
		hash_ctl.keysize = sizeof(Oid);
		hash_ctl.entrysize = sizeof(CFuncHashTabEntry);
		hash_ctl.hash = oid_hash;
		CFuncHash = hash_create("CFuncHash",
								100,
								&hash_ctl,
								HASH_ELEM | HASH_FUNCTION);
	}

	entry = (CFuncHashTabEntry *)
		hash_search(CFuncHash,
					&fn_oid,
					HASH_ENTER,
					&found);
	/* OID is already filled in */
	entry->fn_xmin = HeapTupleHeaderGetXmin(procedureTuple->t_data);
	entry->fn_tid = procedureTuple->t_self;
	entry->user_fn = user_fn;
	entry->inforec = inforec;
}

/*
 * clear_external_function_hash: remove entries for a library being closed
 *
 * Presently we just zap the entire hash table, but later it might be worth
 * the effort to remove only the entries associated with the given handle.
 */
void
clear_external_function_hash(void *filehandle)
{
	if (CFuncHash)
		hash_destroy(CFuncHash);
	CFuncHash = NULL;
}


/*
 * Copy an FmgrInfo struct
 *