/*--------------------------------------------------------------------
 * Symbols referenced in this file:
 * - FunctionCall5Coll
 *--------------------------------------------------------------------
 */

/*-------------------------------------------------------------------------
 *
 * fmgr.c
 *	  The Postgres function manager.
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/backend/utils/fmgr/fmgr.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/detoast.h"
#include "catalog/pg_language.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "executor/functions.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "pgstat.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/fmgrtab.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"

/*
 * Hooks for function calls
 */
PGDLLIMPORT

PGDLLIMPORT


/*
 * 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 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);

/* extern so it's callable via JIT */
extern 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.
 */



/*
 * 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.
 */


/*
 * 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.
 */


/*
 * Fill a FmgrInfo struct, specifying a memory context in which its
 * subsidiary data should go.
 */


/*
 * This one does the actual work.  ignore_security is ordinarily false
 * but is set to true when we need to avoid recursion.
 */


/*
 * Return module and C function name providing implementation of functionId.
 *
 * If *mod == NULL and *fn == NULL, no C symbol is known to implement
 * function.
 *
 * If *mod == NULL and *fn != NULL, the function is implemented by a symbol in
 * the main binary.
 *
 * If *mod != NULL and *fn !=NULL the function is implemented in an extension
 * shared object.
 *
 * The returned module and function names are pstrdup'ed into the current
 * memory context.
 */



/*
 * Special fmgr_info processing for C-language functions.  Note that
 * finfo->fn_oid is not valid yet.
 */


/*
 * Special fmgr_info processing for other-language functions.  Note
 * that finfo->fn_oid is not valid yet.
 */


/*
 * 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 an error is raised.
 *
 * 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.
 */



/*-------------------------------------------------------------------------
 *		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
 */


/*
 * record_C_func: enter (or update) info about a C function in the hash table
 */


/*
 * 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.
 */



/*
 * Copy an FmgrInfo struct
 *
 * This is inherently somewhat bogus since we can't reliably duplicate
 * language-dependent subsidiary info.  We cheat by zeroing fn_extra,
 * instead, meaning that subsidiary info will have to be recomputed.
 */



/*
 * Specialized lookup routine for fmgr_internal_validator: given the alleged
 * name of an internal function, return the OID of the function.
 * If the name is not recognized, return InvalidOid.
 */



/*
 * Support for security-definer and proconfig-using functions.  We support
 * both of these features using the same call handler, because they are
 * often used together and it would be inefficient (as well as notationally
 * messy) to have two levels of call handler involved.
 */
struct fmgr_security_definer_cache
{
	FmgrInfo	flinfo;			/* lookup info for target function */
	Oid			userid;			/* userid to set, or InvalidOid */
	ArrayType  *proconfig;		/* GUC values to set, or NULL */
	Datum		arg;			/* passthrough argument for plugin modules */
};

/*
 * Function handler for security-definer/proconfig/plugin-hooked functions.
 * We extract the OID of the actual function and do a fmgr lookup again.
 * Then we fetch the pg_proc row and copy the owner ID and proconfig fields.
 * (All this info is cached for the duration of the current query.)
 * To execute a call, we temporarily replace the flinfo with the cached
 * and looked-up one, while keeping the outer fcinfo (which contains all
 * the actual arguments, etc.) intact.  This is not re-entrant, but then
 * the fcinfo itself can't be used reentrantly anyway.
 */



/*-------------------------------------------------------------------------
 *		Support routines for callers of fmgr-compatible functions
 *-------------------------------------------------------------------------
 */

/*
 * These are for invocation of a specifically named function with a
 * directly-computed parameter list.  Note that neither arguments nor result
 * are allowed to be NULL.  Also, the function cannot be one that needs to
 * look at FmgrInfo, since there won't be any.
 */


















/*
 * These functions work like the DirectFunctionCall functions except that
 * they use the flinfo parameter to initialise the fcinfo for the call.
 * It's recommended that the callee only use the fn_extra and fn_mcxt
 * fields, as other fields will typically describe the calling function
 * not the callee.  Conversely, the calling function should not have
 * used fn_extra, unless its use is known to be compatible with the callee's.
 */





/*
 * These are for invocation of a previously-looked-up function with a
 * directly-computed parameter list.  Note that neither arguments nor result
 * are allowed to be NULL.
 */










Datum
FunctionCall5Coll(FmgrInfo *flinfo, Oid collation, Datum arg1, Datum arg2,
				  Datum arg3, Datum arg4, Datum arg5)
{
	LOCAL_FCINFO(fcinfo, 5);
	Datum		result;

	InitFunctionCallInfoData(*fcinfo, flinfo, 5, collation, NULL, NULL);

	fcinfo->args[0].value = arg1;
	fcinfo->args[0].isnull = false;
	fcinfo->args[1].value = arg2;
	fcinfo->args[1].isnull = false;
	fcinfo->args[2].value = arg3;
	fcinfo->args[2].isnull = false;
	fcinfo->args[3].value = arg4;
	fcinfo->args[3].isnull = false;
	fcinfo->args[4].value = arg5;
	fcinfo->args[4].isnull = false;

	result = FunctionCallInvoke(fcinfo);

	/* Check for null result, since caller is clearly not expecting one */
	if (fcinfo->isnull)
		elog(ERROR, "function %u returned NULL", flinfo->fn_oid);

	return result;
}










/*
 * These are for invocation of a function identified by OID with a
 * directly-computed parameter list.  Note that neither arguments nor result
 * are allowed to be NULL.  These are essentially fmgr_info() followed
 * by FunctionCallN().  If the same function is to be invoked repeatedly,
 * do the fmgr_info() once and then use FunctionCallN().
 */





















/*
 * Special cases for convenient invocation of datatype I/O functions.
 */

/*
 * Call a previously-looked-up datatype input function.
 *
 * "str" may be NULL to indicate we are reading a NULL.  In this case
 * the caller should assume the result is NULL, but we'll call the input
 * function anyway if it's not strict.  So this is almost but not quite
 * the same as FunctionCall3.
 */


/*
 * Call a previously-looked-up datatype output function.
 *
 * Do not call this on NULL datums.
 *
 * This is currently little more than window dressing for FunctionCall1.
 */


/*
 * Call a previously-looked-up datatype binary-input function.
 *
 * "buf" may be NULL to indicate we are reading a NULL.  In this case
 * the caller should assume the result is NULL, but we'll call the receive
 * function anyway if it's not strict.  So this is almost but not quite
 * the same as FunctionCall3.
 */


/*
 * Call a previously-looked-up datatype binary-output function.
 *
 * Do not call this on NULL datums.
 *
 * This is little more than window dressing for FunctionCall1, but it does
 * guarantee a non-toasted result, which strictly speaking the underlying
 * function doesn't.
 */


/*
 * As above, for I/O functions identified by OID.  These are only to be used
 * in seldom-executed code paths.  They are not only slow but leak memory.
 */









/*-------------------------------------------------------------------------
 *		Support routines for standard maybe-pass-by-reference datatypes
 *
 * int8 and float8 can be passed by value if Datum is wide enough.
 * (For backwards-compatibility reasons, we allow pass-by-ref to be chosen
 * at compile time even if pass-by-val is possible.)
 *
 * Note: there is only one switch controlling the pass-by-value option for
 * both int8 and float8; this is to avoid making things unduly complicated
 * for the timestamp types, which might have either representation.
 *-------------------------------------------------------------------------
 */

#ifndef USE_FLOAT8_BYVAL		/* controls int8 too */

Datum
Int64GetDatum(int64 X)
{
	int64	   *retval = (int64 *) palloc(sizeof(int64));

	*retval = X;
	return PointerGetDatum(retval);
}

Datum
Float8GetDatum(float8 X)
{
	float8	   *retval = (float8 *) palloc(sizeof(float8));

	*retval = X;
	return PointerGetDatum(retval);
}
#endif							/* USE_FLOAT8_BYVAL */


/*-------------------------------------------------------------------------
 *		Support routines for toastable datatypes
 *-------------------------------------------------------------------------
 */









/*-------------------------------------------------------------------------
 *		Support routines for extracting info from fn_expr parse tree
 *
 * These are needed by polymorphic functions, which accept multiple possible
 * input types and need help from the parser to know what they've got.
 * Also, some functions might be interested in whether a parameter is constant.
 * Functions taking VARIADIC ANY also need to know about the VARIADIC keyword.
 *-------------------------------------------------------------------------
 */

/*
 * Get the actual type OID of the function return type
 *
 * Returns InvalidOid if information is not available
 */


/*
 * Get the actual type OID of a specific function argument (counting from 0)
 *
 * Returns InvalidOid if information is not available
 */


/*
 * Get the actual type OID of a specific function argument (counting from 0),
 * but working from the calling expression tree instead of FmgrInfo
 *
 * Returns InvalidOid if information is not available
 */


/*
 * Find out whether a specific function argument is constant for the
 * duration of a query
 *
 * Returns false if information is not available
 */


/*
 * Find out whether a specific function argument is constant for the
 * duration of a query, but working from the calling expression tree
 *
 * Returns false if information is not available
 */


/*
 * Get the VARIADIC flag from the function invocation
 *
 * Returns false (the default assumption) if information is not available
 *
 * Note this is generally only of interest to VARIADIC ANY functions
 */


/*
 * Set options to FmgrInfo of opclass support function.
 *
 * Opclass support functions are called outside of expressions.  Thanks to that
 * we can use fn_expr to store opclass options as bytea constant.
 */


/*
 * Check if options are defined for opclass support function.
 */


/*
 * Get options for opclass support function.
 */


/*-------------------------------------------------------------------------
 *		Support routines for procedural language implementations
 *-------------------------------------------------------------------------
 */

/*
 * Verify that a validator is actually associated with the language of a
 * particular function and that the user has access to both the language and
 * the function.  All validators should call this before doing anything
 * substantial.  Doing so ensures a user cannot achieve anything with explicit
 * calls to validators that he could not achieve with CREATE FUNCTION or by
 * simply calling an existing function.
 *
 * When this function returns false, callers should skip all validation work
 * and call PG_RETURN_VOID().  This never happens at present; it is reserved
 * for future expansion.
 *
 * In particular, checking that the validator corresponds to the function's
 * language allows untrusted language validators to assume they process only
 * superuser-chosen source code.  (Untrusted language call handlers, by
 * definition, do assume that.)  A user lacking the USAGE language privilege
 * would be unable to reach the validator through CREATE FUNCTION, so we check
 * that to block explicit calls as well.  Checking the EXECUTE privilege on
 * the function is often superfluous, because most users can clone the
 * function to get an executable copy.  It is meaningful against users with no
 * database TEMP right and no permanent schema CREATE right, thereby unable to
 * create any function.  Also, if the function tracks persistent state by
 * function OID or name, validating the original function might permit more
 * mischief than creating and validating a clone thereof.
 */