parse_func.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * parse_func.c
 *		handle function calls in parser
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/parser/parse_func.c,v 1.182.2.1 2005/11/22 18:23:14 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "catalog/pg_inherits.h"
#include "catalog/pg_proc.h"
#include "funcapi.h"
#include "lib/stringinfo.h"
#include "nodes/makefuncs.h"
#include "parser/parse_agg.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_func.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#include "parser/parse_type.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"


static Node *ParseComplexProjection(ParseState *pstate, char *funcname,
					   Node *first_arg);
static void unknown_attribute(ParseState *pstate, Node *relref, char *attname);


/*
 *	Parse a function call
 *
 *	For historical reasons, Postgres tries to treat the notations tab.col
 *	and col(tab) as equivalent: if a single-argument function call has an
 *	argument of complex type and the (unqualified) function name matches
 *	any attribute of the type, we take it as a column projection.  Conversely
 *	a function of a single complex-type argument can be written like a
 *	column reference, allowing functions to act like computed columns.
 *
 *	Hence, both cases come through here.  The is_column parameter tells us
 *	which syntactic construct is actually being dealt with, but this is
 *	intended to be used only to deliver an appropriate error message,
 *	not to affect the semantics.  When is_column is true, we should have
 *	a single argument (the putative table), unqualified function name
 *	equal to the column name, and no aggregate decoration.
 *
 *	The argument expressions (in fargs) must have been transformed already.
 */
Node *
ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
				  bool agg_star, bool agg_distinct, bool is_column)
{
	Oid			rettype;
	Oid			funcid;
	ListCell   *l;
	ListCell   *nextl;
	Node	   *first_arg = NULL;
	int			nargs;
	Oid			actual_arg_types[FUNC_MAX_ARGS];
	Oid		   *declared_arg_types;
	Node	   *retval;
	bool		retset;
	FuncDetailCode fdresult;

	/*
	 * Most of the rest of the parser just assumes that functions do not have
	 * more than FUNC_MAX_ARGS parameters.	We have to test here to protect
	 * against array overruns, etc.  Of course, this may not be a function,
	 * but the test doesn't hurt.
	 */
	if (list_length(fargs) > FUNC_MAX_ARGS)
		ereport(ERROR,
				(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
				 errmsg("cannot pass more than %d arguments to a function",
						FUNC_MAX_ARGS)));

	/*
	 * Extract arg type info in preparation for function lookup.
	 *
	 * If any arguments are Param markers of type VOID, we discard them from
	 * the parameter list.	This is a hack to allow the JDBC driver to not
	 * have to distinguish "input" and "output" parameter symbols while
	 * parsing function-call constructs.  We can't use foreach() because we
	 * may modify the list ...
	 */
	nargs = 0;
	for (l = list_head(fargs); l != NULL; l = nextl)
	{
		Node	   *arg = lfirst(l);
		Oid			argtype = exprType(arg);

		nextl = lnext(l);

		if (argtype == VOIDOID && IsA(arg, Param) &&!is_column)
		{
			fargs = list_delete_ptr(fargs, arg);
			continue;
		}

		actual_arg_types[nargs++] = argtype;
	}

	if (fargs)
	{
		first_arg = linitial(fargs);
		Assert(first_arg != NULL);
	}

	/*
	 * Check for column projection: if function has one argument, and that
	 * argument is of complex type, and function name is not qualified, then
	 * the "function call" could be a projection.  We also check that there
	 * wasn't any aggregate decoration.
	 */
	if (nargs == 1 && !agg_star && !agg_distinct && list_length(funcname) == 1)
	{
		Oid			argtype = actual_arg_types[0];

		if (argtype == RECORDOID || ISCOMPLEX(argtype))
		{
			retval = ParseComplexProjection(pstate,
											strVal(linitial(funcname)),
											first_arg);
			if (retval)
				return retval;

			/*
			 * If ParseComplexProjection doesn't recognize it as a projection,
			 * just press on.
			 */
		}
	}

	/*
	 * Okay, it's not a column projection, so it must really be a function.
	 * func_get_detail looks up the function in the catalogs, does
	 * disambiguation for polymorphic functions, handles inheritance, and
	 * returns the funcid and type and set or singleton status of the
	 * function's return value.  it also returns the true argument types to
	 * the function.
	 */
	fdresult = func_get_detail(funcname, fargs, nargs, actual_arg_types,
							   &funcid, &rettype, &retset,
							   &declared_arg_types);
	if (fdresult == FUNCDETAIL_COERCION)
	{
		/*
		 * We can do it as a trivial coercion. coerce_type can handle these
		 * cases, so why duplicate code...
		 */
		return coerce_type(pstate, linitial(fargs),
						   actual_arg_types[0], rettype, -1,
						   COERCION_EXPLICIT, COERCE_EXPLICIT_CALL);
	}
	else if (fdresult == FUNCDETAIL_NORMAL)
	{
		/*
		 * Normal function found; was there anything indicating it must be an
		 * aggregate?
		 */
		if (agg_star)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
			   errmsg("%s(*) specified, but %s is not an aggregate function",
					  NameListToString(funcname),
					  NameListToString(funcname))));
		if (agg_distinct)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
			errmsg("DISTINCT specified, but %s is not an aggregate function",
				   NameListToString(funcname))));
	}
	else if (fdresult != FUNCDETAIL_AGGREGATE)
	{
		/*
		 * Oops.  Time to die.
		 *
		 * If we are dealing with the attribute notation rel.function, give an
		 * error message that is appropriate for that case.
		 */
		if (is_column)
		{
			Assert(nargs == 1);
			Assert(list_length(funcname) == 1);
			unknown_attribute(pstate, first_arg, strVal(linitial(funcname)));
		}

		/*
		 * Else generate a detailed complaint for a function
		 */
		if (fdresult == FUNCDETAIL_MULTIPLE)
			ereport(ERROR,
					(errcode(ERRCODE_AMBIGUOUS_FUNCTION),
					 errmsg("function %s is not unique",
							func_signature_string(funcname, nargs,
												  actual_arg_types)),
					 errhint("Could not choose a best candidate function. "
							 "You may need to add explicit type casts.")));
		else
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_FUNCTION),
					 errmsg("function %s does not exist",
							func_signature_string(funcname, nargs,
												  actual_arg_types)),
			errhint("No function matches the given name and argument types. "
					"You may need to add explicit type casts.")));
	}

	/*
	 * enforce consistency with ANYARRAY and ANYELEMENT argument and return
	 * types, possibly adjusting return type or declared_arg_types (which will
	 * be used as the cast destination by make_fn_arguments)
	 */
	rettype = enforce_generic_type_consistency(actual_arg_types,
											   declared_arg_types,
											   nargs,
											   rettype);

	/* perform the necessary typecasting of arguments */
	make_fn_arguments(pstate, fargs, actual_arg_types, declared_arg_types);

	/* build the appropriate output structure */
	if (fdresult == FUNCDETAIL_NORMAL)
	{
		FuncExpr   *funcexpr = makeNode(FuncExpr);

		funcexpr->funcid = funcid;
		funcexpr->funcresulttype = rettype;
		funcexpr->funcretset = retset;
		funcexpr->funcformat = COERCE_EXPLICIT_CALL;
		funcexpr->args = fargs;

		retval = (Node *) funcexpr;
	}
	else
	{
		/* aggregate function */
		Aggref	   *aggref = makeNode(Aggref);

		aggref->aggfnoid = funcid;
		aggref->aggtype = rettype;
		aggref->target = linitial(fargs);
		aggref->aggstar = agg_star;
		aggref->aggdistinct = agg_distinct;

		/* parse_agg.c does additional aggregate-specific processing */
		transformAggregateCall(pstate, aggref);

		retval = (Node *) aggref;

		if (retset)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_FUNCTION_DEFINITION),
					 errmsg("aggregates may not return sets")));
	}

	return retval;
}


/* func_match_argtypes()
 *
 * Given a list of candidate functions (having the right name and number
 * of arguments) and an array of input datatype OIDs, produce a shortlist of
 * those candidates that actually accept the input datatypes (either exactly
 * or by coercion), and return the number of such candidates.
 *
 * Note that can_coerce_type will assume that UNKNOWN inputs are coercible to
 * anything, so candidates will not be eliminated on that basis.
 *
 * NB: okay to modify input list structure, as long as we find at least
 * one match.  If no match at all, the list must remain unmodified.
 */
int
func_match_argtypes(int nargs,
					Oid *input_typeids,
					FuncCandidateList raw_candidates,
					FuncCandidateList *candidates)		/* return value */
{
	FuncCandidateList current_candidate;
	FuncCandidateList next_candidate;
	int			ncandidates = 0;

	*candidates = NULL;

	for (current_candidate = raw_candidates;
		 current_candidate != NULL;
		 current_candidate = next_candidate)
	{
		next_candidate = current_candidate->next;
		if (can_coerce_type(nargs, input_typeids, current_candidate->args,
							COERCION_IMPLICIT))
		{
			current_candidate->next = *candidates;
			*candidates = current_candidate;
			ncandidates++;
		}
	}

	return ncandidates;
}	/* func_match_argtypes() */


/* func_select_candidate()
 *		Given the input argtype array and more than one candidate
 *		for the function, attempt to resolve the conflict.
 *
 * Returns the selected candidate if the conflict can be resolved,
 * otherwise returns NULL.
 *
 * Note that the caller has already determined that there is no candidate
 * exactly matching the input argtypes, and has pruned away any "candidates"
 * that aren't actually coercion-compatible with the input types.
 *
 * This is also used for resolving ambiguous operator references.  Formerly
 * parse_oper.c had its own, essentially duplicate code for the purpose.
 * The following comments (formerly in parse_oper.c) are kept to record some
 * of the history of these heuristics.
 *
 * OLD COMMENTS:
 *
 * This routine is new code, replacing binary_oper_select_candidate()
 * which dates from v4.2/v1.0.x days. It tries very hard to match up
 * operators with types, including allowing type coercions if necessary.
 * The important thing is that the code do as much as possible,
 * while _never_ doing the wrong thing, where "the wrong thing" would
 * be returning an operator when other better choices are available,
 * or returning an operator which is a non-intuitive possibility.
 * - thomas 1998-05-21
 *
 * The comments below came from binary_oper_select_candidate(), and
 * illustrate the issues and choices which are possible:
 * - thomas 1998-05-20
 *
 * current wisdom holds that the default operator should be one in which
 * both operands have the same type (there will only be one such
 * operator)
 *
 * 7.27.93 - I have decided not to do this; it's too hard to justify, and
 * it's easy enough to typecast explicitly - avi
 * [the rest of this routine was commented out since then - ay]
 *
 * 6/23/95 - I don't complete agree with avi. In particular, casting
 * floats is a pain for users. Whatever the rationale behind not doing
 * this is, I need the following special case to work.
 *
 * In the WHERE clause of a query, if a float is specified without
 * quotes, we treat it as float8. I added the float48* operators so
 * that we can operate on float4 and float8. But now we have more than
 * one matching operator if the right arg is unknown (eg. float
 * specified with quotes). This break some stuff in the regression
 * test where there are floats in quotes not properly casted. Below is
 * the solution. In addition to requiring the operator operates on the
 * same type for both operands [as in the code Avi originally
 * commented out], we also require that the operators be equivalent in
 * some sense. (see equivalentOpersAfterPromotion for details.)
 * - ay 6/95
 */
FuncCandidateList
func_select_candidate(int nargs,
					  Oid *input_typeids,
					  FuncCandidateList candidates)
{
	FuncCandidateList current_candidate;
	FuncCandidateList last_candidate;
	Oid		   *current_typeids;
	Oid			current_type;
	int			i;
	int			ncandidates;
	int			nbestMatch,
				nmatch;
	Oid			input_base_typeids[FUNC_MAX_ARGS];
	CATEGORY	slot_category[FUNC_MAX_ARGS],
				current_category;
	bool		slot_has_preferred_type[FUNC_MAX_ARGS];
	bool		resolved_unknowns;

	/* protect local fixed-size arrays */
	if (nargs > FUNC_MAX_ARGS)
		ereport(ERROR,
				(errcode(ERRCODE_TOO_MANY_ARGUMENTS),
				 errmsg("cannot pass more than %d arguments to a function",
						FUNC_MAX_ARGS)));

	/*
	 * If any input types are domains, reduce them to their base types. This
	 * ensures that we will consider functions on the base type to be "exact
	 * matches" in the exact-match heuristic; it also makes it possible to do
	 * something useful with the type-category heuristics. Note that this
	 * makes it difficult, but not impossible, to use functions declared to
	 * take a domain as an input datatype.	Such a function will be selected
	 * over the base-type function only if it is an exact match at all
	 * argument positions, and so was already chosen by our caller.
	 */
	for (i = 0; i < nargs; i++)
		input_base_typeids[i] = getBaseType(input_typeids[i]);

	/*
	 * Run through all candidates and keep those with the most matches on
	 * exact types. Keep all candidates if none match.
	 */