parse_coerce.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * parse_coerce.c
 *		handle type coercions/conversions for 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_coerce.c,v 2.132.2.3 2006/01/17 17:33:20 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "catalog/pg_cast.h"
#include "catalog/pg_proc.h"
#include "nodes/makefuncs.h"
#include "nodes/params.h"
#include "optimizer/clauses.h"
#include "parser/parsetree.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_func.h"
#include "parser/parse_relation.h"
#include "parser/parse_type.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
#include "utils/typcache.h"


static Node *coerce_type_typmod(Node *node,
				   Oid targetTypeId, int32 targetTypMod,
				   CoercionForm cformat, bool isExplicit,
				   bool hideInputCoercion);
static void hide_coercion_node(Node *node);
static Node *build_coercion_expression(Node *node, Oid funcId,
						  Oid targetTypeId, int32 targetTypMod,
						  CoercionForm cformat, bool isExplicit);
static Node *coerce_record_to_complex(ParseState *pstate, Node *node,
						 Oid targetTypeId,
						 CoercionContext ccontext,
						 CoercionForm cformat);


/*
 * coerce_to_target_type()
 *		Convert an expression to a target type and typmod.
 *
 * This is the general-purpose entry point for arbitrary type coercion
 * operations.	Direct use of the component operations can_coerce_type,
 * coerce_type, and coerce_type_typmod should be restricted to special
 * cases (eg, when the conversion is expected to succeed).
 *
 * Returns the possibly-transformed expression tree, or NULL if the type
 * conversion is not possible.	(We do this, rather than ereport'ing directly,
 * so that callers can generate custom error messages indicating context.)
 *
 * pstate - parse state (can be NULL, see coerce_type)
 * expr - input expression tree (already transformed by transformExpr)
 * exprtype - result type of expr
 * targettype - desired result type
 * targettypmod - desired result typmod
 * ccontext, cformat - context indicators to control coercions
 */
Node *
coerce_to_target_type(ParseState *pstate, Node *expr, Oid exprtype,
					  Oid targettype, int32 targettypmod,
					  CoercionContext ccontext,
					  CoercionForm cformat)
{
	Node	   *result;

	if (!can_coerce_type(1, &exprtype, &targettype, ccontext))
		return NULL;

	result = coerce_type(pstate, expr, exprtype,
						 targettype, targettypmod,
						 ccontext, cformat);

	/*
	 * If the target is a fixed-length type, it may need a length coercion as
	 * well as a type coercion.  If we find ourselves adding both, force the
	 * inner coercion node to implicit display form.
	 */
	result = coerce_type_typmod(result,
								targettype, targettypmod,
								cformat,
								(cformat != COERCE_IMPLICIT_CAST),
								(result != expr && !IsA(result, Const)));

	return result;
}


/*
 * coerce_type()
 *		Convert an expression to a different type.
 *
 * The caller should already have determined that the coercion is possible;
 * see can_coerce_type.
 *
 * Normally, no coercion to a typmod (length) is performed here.  The caller
 * must call coerce_type_typmod as well, if a typmod constraint is wanted.
 * (But if the target type is a domain, it may internally contain a
 * typmod constraint, which will be applied inside coerce_to_domain.)
 * In some cases pg_cast specifies a type coercion function that also
 * applies length conversion, and in those cases only, the result will
 * already be properly coerced to the specified typmod.
 *
 * pstate is only used in the case that we are able to resolve the type of
 * a previously UNKNOWN Param.	It is okay to pass pstate = NULL if the
 * caller does not want type information updated for Params.
 */
Node *
coerce_type(ParseState *pstate, Node *node,
			Oid inputTypeId, Oid targetTypeId, int32 targetTypeMod,
			CoercionContext ccontext, CoercionForm cformat)
{
	Node	   *result;
	Oid			funcId;

	if (targetTypeId == inputTypeId ||
		node == NULL)
	{
		/* no conversion needed */
		return node;
	}
	if (targetTypeId == ANYOID ||
		targetTypeId == ANYARRAYOID ||
		targetTypeId == ANYELEMENTOID)
	{
		/* assume can_coerce_type verified that implicit coercion is okay */
		/* NB: we do NOT want a RelabelType here */
		return node;
	}
	if (inputTypeId == UNKNOWNOID && IsA(node, Const))
	{
		/*
		 * Input is a string constant with previously undetermined type. Apply
		 * the target type's typinput function to it to produce a constant of
		 * the target type.
		 *
		 * NOTE: this case cannot be folded together with the other
		 * constant-input case, since the typinput function does not
		 * necessarily behave the same as a type conversion function. For
		 * example, int4's typinput function will reject "1.2", whereas
		 * float-to-int type conversion will round to integer.
		 *
		 * XXX if the typinput function is not immutable, we really ought to
		 * postpone evaluation of the function call until runtime. But there
		 * is no way to represent a typinput function call as an expression
		 * tree, because C-string values are not Datums. (XXX This *is*
		 * possible as of 7.3, do we want to do it?)
		 */
		Const	   *con = (Const *) node;
		Const	   *newcon = makeNode(Const);
		Type		targetType = typeidType(targetTypeId);
		char		targetTyptype = typeTypType(targetType);

		newcon->consttype = targetTypeId;
		newcon->constlen = typeLen(targetType);
		newcon->constbyval = typeByVal(targetType);
		newcon->constisnull = con->constisnull;

		if (!con->constisnull)
		{
			/*
			 * We assume here that UNKNOWN's internal representation is the
			 * same as CSTRING
			 */
			char	   *val = DatumGetCString(con->constvalue);

			/*
			 * We pass typmod -1 to the input routine, primarily because
			 * existing input routines follow implicit-coercion semantics for
			 * length checks, which is not always what we want here. Any
			 * length constraint will be applied later by our caller.
			 *
			 * Note that we call stringTypeDatum using the domain's pg_type
			 * row, if it's a domain.  This works because the domain row has
			 * the same typinput and typelem as the base type --- ugly...
			 */
			newcon->constvalue = stringTypeDatum(targetType, val, -1);
		}

		result = (Node *) newcon;

		/* If target is a domain, apply constraints. */
		if (targetTyptype == 'd')
			result = coerce_to_domain(result, InvalidOid, targetTypeId,
									  cformat, false, false);

		ReleaseSysCache(targetType);

		return result;
	}
	if (inputTypeId == UNKNOWNOID && IsA(node, Param) &&
		((Param *) node)->paramkind == PARAM_NUM &&
		pstate != NULL && pstate->p_variableparams)
	{
		/*
		 * Input is a Param of previously undetermined type, and we want to
		 * update our knowledge of the Param's type.  Find the topmost
		 * ParseState and update the state.
		 */
		Param	   *param = (Param *) node;
		int			paramno = param->paramid;
		ParseState *toppstate;

		toppstate = pstate;
		while (toppstate->parentParseState != NULL)
			toppstate = toppstate->parentParseState;

		if (paramno <= 0 ||		/* shouldn't happen, but... */
			paramno > toppstate->p_numparams)
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_PARAMETER),
					 errmsg("there is no parameter $%d", paramno)));

		if (toppstate->p_paramtypes[paramno - 1] == UNKNOWNOID)
		{
			/* We've successfully resolved the type */
			toppstate->p_paramtypes[paramno - 1] = targetTypeId;
		}
		else if (toppstate->p_paramtypes[paramno - 1] == targetTypeId)
		{
			/* We previously resolved the type, and it matches */
		}
		else
		{
			/* Ooops */
			ereport(ERROR,
					(errcode(ERRCODE_AMBIGUOUS_PARAMETER),
					 errmsg("inconsistent types deduced for parameter $%d",
							paramno),
					 errdetail("%s versus %s",
						format_type_be(toppstate->p_paramtypes[paramno - 1]),
							   format_type_be(targetTypeId))));
		}

		param->paramtype = targetTypeId;

		/* Apply domain constraints, if necessary */
		return coerce_to_domain((Node *) param, InvalidOid, targetTypeId,
								cformat, false, false);
	}
	if (find_coercion_pathway(targetTypeId, inputTypeId, ccontext,
							  &funcId))
	{
		if (OidIsValid(funcId))
		{
			/*
			 * Generate an expression tree representing run-time application
			 * of the conversion function.	If we are dealing with a domain
			 * target type, the conversion function will yield the base type,
			 * and we need to extract the correct typmod to use from the
			 * domain's typtypmod.
			 */
			Oid			baseTypeId = getBaseType(targetTypeId);
			int32		baseTypeMod;

			if (targetTypeId != baseTypeId)
				baseTypeMod = get_typtypmod(targetTypeId);
			else
				baseTypeMod = targetTypeMod;

			result = build_coercion_expression(node, funcId,
											   baseTypeId, baseTypeMod,
											   cformat,
										  (cformat != COERCE_IMPLICIT_CAST));

			/*
			 * If domain, coerce to the domain type and relabel with domain
			 * type ID.  We can skip the internal length-coercion step if the
			 * selected coercion function was a type-and-length coercion.
			 */
			if (targetTypeId != baseTypeId)
				result = coerce_to_domain(result, baseTypeId, targetTypeId,
										  cformat, true,
										  exprIsLengthCoercion(result,
															   NULL));
		}
		else
		{
			/*
			 * We don't need to do a physical conversion, but we do need to
			 * attach a RelabelType node so that the expression will be seen
			 * to have the intended type when inspected by higher-level code.
			 *
			 * Also, domains may have value restrictions beyond the base type
			 * that must be accounted for.	If the destination is a domain
			 * then we won't need a RelabelType node.
			 */
			result = coerce_to_domain(node, InvalidOid, targetTypeId,
									  cformat, false, false);
			if (result == node)
			{
				/*
				 * XXX could we label result with exprTypmod(node) instead of
				 * default -1 typmod, to save a possible length-coercion
				 * later? Would work if both types have same interpretation of
				 * typmod, which is likely but not certain.
				 */
				result = (Node *) makeRelabelType((Expr *) result,
												  targetTypeId, -1,
												  cformat);
			}
		}
		return result;
	}
	if (inputTypeId == RECORDOID &&
		ISCOMPLEX(targetTypeId))
	{
		/* Coerce a RECORD to a specific complex type */
		return coerce_record_to_complex(pstate, node, targetTypeId,
										ccontext, cformat);
	}
	if (targetTypeId == RECORDOID &&
		ISCOMPLEX(inputTypeId))
	{
		/* Coerce a specific complex type to RECORD */
		/* NB: we do NOT want a RelabelType here */
		return node;
	}
	if (typeInheritsFrom(inputTypeId, targetTypeId))
	{
		/*
		 * Input class type is a subclass of target, so generate an
		 * appropriate runtime conversion (removing unneeded columns and
		 * possibly rearranging the ones that are wanted).
		 */
		ConvertRowtypeExpr *r = makeNode(ConvertRowtypeExpr);

		r->arg = (Expr *) node;
		r->resulttype = targetTypeId;
		r->convertformat = cformat;
		return (Node *) r;
	}
	/* If we get here, caller blew it */
	elog(ERROR, "failed to find conversion function from %s to %s",
		 format_type_be(inputTypeId), format_type_be(targetTypeId));
	return NULL;				/* keep compiler quiet */
}


/*
 * can_coerce_type()
 *		Can input_typeids be coerced to target_typeids?
 *
 * We must be told the context (CAST construct, assignment, implicit coercion)
 * as this determines the set of available casts.
 */
bool
can_coerce_type(int nargs, Oid *input_typeids, Oid *target_typeids,
				CoercionContext ccontext)
{
	bool		have_generics = false;
	int			i;

	/* run through argument list... */
	for (i = 0; i < nargs; i++)
	{
		Oid			inputTypeId = input_typeids[i];
		Oid			targetTypeId = target_typeids[i];
		Oid			funcId;

		/* no problem if same type */
		if (inputTypeId == targetTypeId)
			continue;

		/* accept if target is ANY */
		if (targetTypeId == ANYOID)
			continue;

		/* accept if target is ANYARRAY or ANYELEMENT, for now */
		if (targetTypeId == ANYARRAYOID ||
			targetTypeId == ANYELEMENTOID)
		{
			have_generics = true;		/* do more checking later */
			continue;
		}

		/*
		 * If input is an untyped string constant, assume we can convert it to
		 * anything.
		 */
		if (inputTypeId == UNKNOWNOID)
			continue;

		/*
		 * If pg_cast shows that we can coerce, accept.  This test now covers
		 * both binary-compatible and coercion-function cases.
		 */
		if (find_coercion_pathway(targetTypeId, inputTypeId, ccontext,
								  &funcId))
			continue;

		/*
		 * If input is RECORD and target is a composite type, assume we can
		 * coerce (may need tighter checking here)
		 */
		if (inputTypeId == RECORDOID &&
			ISCOMPLEX(targetTypeId))
			continue;

		/*
		 * If input is a composite type and target is RECORD, accept
		 */
		if (targetTypeId == RECORDOID &&
			ISCOMPLEX(inputTypeId))
			continue;

		/*
		 * If input is a class type that inherits from target, accept
		 */
		if (typeInheritsFrom(inputTypeId, targetTypeId))
			continue;

		/*
		 * Else, cannot coerce at this argument position
		 */
		return false;
	}

	/* If we found any generic argument types, cross-check them */
	if (have_generics)
	{
		if (!check_generic_type_consistency(input_typeids, target_typeids,
											nargs))
			return false;
	}

	return true;
}


/*
 * Create an expression tree to represent coercion to a domain type.
 *
 * 'arg': input expression
 * 'baseTypeId': base type of domain, if known (pass InvalidOid if caller