parse_expr.c

关系型数据库 Postgresql 6.5.2

/*-------------------------------------------------------------------------
 *
 * parse_expr.c
 *	  handle expressions in parser
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $Header: /usr/local/cvsroot/pgsql/src/backend/parser/parse_expr.c,v 1.50.2.1 1999/09/13 04:21:21 thomas Exp $
 *
 *-------------------------------------------------------------------------
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "postgres.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "nodes/nodes.h"
#include "nodes/params.h"
#include "nodes/relation.h"
#include "parse.h"
#include "parser/analyze.h"
#include "parser/gramparse.h"
#include "parser/parse_expr.h"
#include "parser/parse_func.h"
#include "parser/parse_node.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#include "parser/parse_coerce.h"
#include "utils/builtins.h"

static Node *parser_typecast(Value *expr, TypeName *typename, int32 atttypmod);
static Node *transformIdent(ParseState *pstate, Node *expr, int precedence);

/*
 * transformExpr -
 *	  analyze and transform expressions. Type checking and type casting is
 *	  done here. The optimizer and the executor cannot handle the original
 *	  (raw) expressions collected by the parse tree. Hence the transformation
 *	  here.
 */
Node *
transformExpr(ParseState *pstate, Node *expr, int precedence)
{
	Node	   *result = NULL;

	if (expr == NULL)
		return NULL;

	switch (nodeTag(expr))
	{
		case T_Attr:
			{
				Attr	   *att = (Attr *) expr;
				Node	   *temp;

				/* what if att.attrs == "*"? */
				temp = ParseNestedFuncOrColumn(pstate, att, &pstate->p_last_resno,
											   precedence);
				if (att->indirection != NIL)
				{
					List	   *idx = att->indirection;

					while (idx != NIL)
					{
						A_Indices  *ai = (A_Indices *) lfirst(idx);
						Node	   *lexpr = NULL,
								   *uexpr;

						uexpr = transformExpr(pstate, ai->uidx, precedence);	/* must exists */
						if (exprType(uexpr) != INT4OID)
							elog(ERROR, "array index expressions must be int4's");
						if (ai->lidx != NULL)
						{
							lexpr = transformExpr(pstate, ai->lidx, precedence);
							if (exprType(lexpr) != INT4OID)
								elog(ERROR, "array index expressions must be int4's");
						}
						ai->lidx = lexpr;
						ai->uidx = uexpr;

						/*
						 * note we reuse the list of indices, make sure we
						 * don't free them! Otherwise, make a new list
						 * here
						 */
						idx = lnext(idx);
					}
					result = (Node *) make_array_ref(temp, att->indirection);
				}
				else
					result = temp;
				break;
			}
		case T_A_Const:
			{
				A_Const    *con = (A_Const *) expr;
				Value	   *val = &con->val;

				if (con->typename != NULL)
					result = parser_typecast(val, con->typename, -1);
				else
					result = (Node *) make_const(val);
				break;
			}
		case T_ParamNo:
			{
				ParamNo    *pno = (ParamNo *) expr;
				Oid			toid;
				int			paramno;
				Param	   *param;

				paramno = pno->number;
				toid = param_type(paramno);
				if (!OidIsValid(toid))
					elog(ERROR, "Parameter '$%d' is out of range", paramno);
				param = makeNode(Param);
				param->paramkind = PARAM_NUM;
				param->paramid = (AttrNumber) paramno;
				param->paramname = "<unnamed>";
				param->paramtype = (Oid) toid;
				param->param_tlist = (List *) NULL;

				if (pno->indirection != NIL)
				{
					List	   *idx = pno->indirection;

					while (idx != NIL)
					{
						A_Indices  *ai = (A_Indices *) lfirst(idx);
						Node	   *lexpr = NULL,
								   *uexpr;

						uexpr = transformExpr(pstate, ai->uidx, precedence);	/* must exists */
						if (exprType(uexpr) != INT4OID)
							elog(ERROR, "array index expressions must be int4's");
						if (ai->lidx != NULL)
						{
							lexpr = transformExpr(pstate, ai->lidx, precedence);
							if (exprType(lexpr) != INT4OID)
								elog(ERROR, "array index expressions must be int4's");
						}
						ai->lidx = lexpr;
						ai->uidx = uexpr;

						/*
						 * note we reuse the list of indices, make sure we
						 * don't free them! Otherwise, make a new list
						 * here
						 */
						idx = lnext(idx);
					}
					result = (Node *) make_array_ref((Node *) param, pno->indirection);
				}
				else
					result = (Node *) param;
				break;
			}
		case T_A_Expr:
			{
				A_Expr	   *a = (A_Expr *) expr;

				switch (a->oper)
				{
					case OP:
						{
							Node	   *lexpr = transformExpr(pstate, a->lexpr, precedence);
							Node	   *rexpr = transformExpr(pstate, a->rexpr, precedence);

							result = (Node *) make_op(a->opname, lexpr, rexpr);
						}
						break;
					case ISNULL:
						{
							Node	   *lexpr = transformExpr(pstate, a->lexpr, precedence);

							result = ParseFuncOrColumn(pstate,
										  "nullvalue", lcons(lexpr, NIL),
												   &pstate->p_last_resno,
													   precedence);
						}
						break;
					case NOTNULL:
						{
							Node	   *lexpr = transformExpr(pstate, a->lexpr, precedence);

							result = ParseFuncOrColumn(pstate,
									   "nonnullvalue", lcons(lexpr, NIL),
												   &pstate->p_last_resno,
													   precedence);
						}
						break;
					case AND:
						{
							Expr	   *expr = makeNode(Expr);
							Node	   *lexpr = transformExpr(pstate, a->lexpr, precedence);
							Node	   *rexpr = transformExpr(pstate, a->rexpr, precedence);

							if (exprType(lexpr) != BOOLOID)
								elog(ERROR, "left-hand side of AND is type '%s', not bool",
									 typeidTypeName(exprType(lexpr)));

							if (exprType(rexpr) != BOOLOID)
								elog(ERROR, "right-hand side of AND is type '%s', not bool",
									 typeidTypeName(exprType(rexpr)));

							expr->typeOid = BOOLOID;
							expr->opType = AND_EXPR;
							expr->args = makeList(lexpr, rexpr, -1);
							result = (Node *) expr;
						}
						break;
					case OR:
						{
							Expr	   *expr = makeNode(Expr);
							Node	   *lexpr = transformExpr(pstate, a->lexpr, precedence);
							Node	   *rexpr = transformExpr(pstate, a->rexpr, precedence);

							if (exprType(lexpr) != BOOLOID)
								elog(ERROR, "left-hand side of OR is type '%s', not bool",
									 typeidTypeName(exprType(lexpr)));
							if (exprType(rexpr) != BOOLOID)
								elog(ERROR, "right-hand side of OR is type '%s', not bool",
									 typeidTypeName(exprType(rexpr)));
							expr->typeOid = BOOLOID;
							expr->opType = OR_EXPR;
							expr->args = makeList(lexpr, rexpr, -1);
							result = (Node *) expr;
						}
						break;
					case NOT:
						{
							Expr	   *expr = makeNode(Expr);
							Node	   *rexpr = transformExpr(pstate, a->rexpr, precedence);

							if (exprType(rexpr) != BOOLOID)
								elog(ERROR, "argument to NOT is type '%s', not bool",
									 typeidTypeName(exprType(rexpr)));
							expr->typeOid = BOOLOID;
							expr->opType = NOT_EXPR;
							expr->args = makeList(rexpr, -1);
							result = (Node *) expr;
						}
						break;
				}
				break;
			}
		case T_Ident:
			{

				/*
				 * look for a column name or a relation name (the default
				 * behavior)
				 */
				result = transformIdent(pstate, expr, precedence);
				break;
			}
		case T_FuncCall:
			{
				FuncCall   *fn = (FuncCall *) expr;
				List	   *args;

				/* transform the list of arguments */
				foreach(args, fn->args)
					lfirst(args) = transformExpr(pstate, (Node *) lfirst(args), precedence);
				result = ParseFuncOrColumn(pstate,
										   fn->funcname,
										   fn->args,
										   &pstate->p_last_resno,
										   precedence);
				break;
			}
		case T_SubLink:
			{
				SubLink    *sublink = (SubLink *) expr;
				List	   *qtrees;
				Query	   *qtree;

				pstate->p_hasSubLinks = true;
				qtrees = parse_analyze(lcons(sublink->subselect, NIL), pstate);
				if (length(qtrees) != 1)
					elog(ERROR, "parser: bad query in subselect");
				qtree = (Query *) lfirst(qtrees);
				if (qtree->commandType != CMD_SELECT ||
					qtree->resultRelation != 0)
					elog(ERROR, "parser: bad query in subselect");
				sublink->subselect = (Node *) qtree;

				if (sublink->subLinkType != EXISTS_SUBLINK)
				{
					char	   *op = lfirst(sublink->oper);
					List	   *left_list = sublink->lefthand;
					List	   *right_list = qtree->targetList;
					List	   *elist;

					foreach(elist, left_list)
						lfirst(elist) = transformExpr(pstate, lfirst(elist),
													  precedence);

					if (length(left_list) > 1 &&
						strcmp(op, "=") != 0 && strcmp(op, "<>") != 0)
						elog(ERROR, "parser: '%s' is not relational operator",
							 op);

					sublink->oper = NIL;

					/* Scan subquery's targetlist to find values that will be
					 * matched against lefthand values.  We need to ignore
					 * resjunk targets, so doing the outer iteration over
					 * right_list is easier than doing it over left_list.
					 */
					while (right_list != NIL)
					{
						TargetEntry *tent = (TargetEntry *) lfirst(right_list);
						Node	   *lexpr;
						Expr	   *op_expr;

						if (! tent->resdom->resjunk)
						{
							if (left_list == NIL)
								elog(ERROR, "parser: Subselect has too many fields.");
							lexpr = lfirst(left_list);
							left_list = lnext(left_list);
							op_expr = make_op(op, lexpr, tent->expr);
							if (op_expr->typeOid != BOOLOID &&
								sublink->subLinkType != EXPR_SUBLINK)
								elog(ERROR, "parser: '%s' must return 'bool' to be used with quantified predicate subquery", op);
							sublink->oper = lappend(sublink->oper, op_expr);
						}
						right_list = lnext(right_list);
					}
					if (left_list != NIL)
						elog(ERROR, "parser: Subselect has too few fields.");
				}
				else
					sublink->oper = NIL;
				result = (Node *) expr;
				break;
			}

		case T_CaseExpr:
			{
				CaseExpr   *c = (CaseExpr *) expr;
				CaseWhen   *w;
				List	   *args;
				Oid			ptype;
				CATEGORY	pcategory;

				/* transform the list of arguments */
				foreach(args, c->args)
				{
					w = lfirst(args);
					if (c->arg != NULL)
					{
						/* shorthand form was specified, so expand... */
						A_Expr	   *a = makeNode(A_Expr);

						a->oper = OP;
						a->opname = "=";
						a->lexpr = c->arg;
						a->rexpr = w->expr;
						w->expr = (Node *) a;
					}
					lfirst(args) = transformExpr(pstate, (Node *) w, precedence);
				}

				/*
				 * It's not shorthand anymore, so drop the implicit
				 * argument. This is necessary to keep the executor from
				 * seeing an untransformed expression...
				 */
				c->arg = NULL;

				/* transform the default clause */
				if (c->defresult == NULL)
				{
					A_Const    *n = makeNode(A_Const);

					n->val.type = T_Null;
					c->defresult = (Node *) n;
				}
				c->defresult = transformExpr(pstate, (Node *) c->defresult, precedence);

				/* now check types across result clauses... */
				c->casetype = exprType(c->defresult);
				ptype = c->casetype;
				pcategory = TypeCategory(ptype);
				foreach(args, c->args)
				{
					Oid			wtype;

					w = lfirst(args);
					wtype = exprType(w->result);
					/* move on to next one if no new information... */
					if (wtype && (wtype != UNKNOWNOID)
						&& (wtype != ptype))
					{
						/* so far, only nulls so take anything... */
						if (!ptype)
						{
							ptype = wtype;
							pcategory = TypeCategory(ptype);
						}

						/*
						 * both types in different categories? then not
						 * much hope...
						 */
						else if ((TypeCategory(wtype) != pcategory)
								 || ((TypeCategory(wtype) == USER_TYPE)
							&& (TypeCategory(c->casetype) == USER_TYPE)))
						{
							elog(ERROR, "CASE/WHEN types '%s' and '%s' not matched",
								 typeidTypeName(c->casetype), typeidTypeName(wtype));
						}

						/*
						 * new one is preferred and can convert? then take
						 * it...
						 */
						else if (IsPreferredType(pcategory, wtype)
								 && can_coerce_type(1, &ptype, &wtype))
						{
							ptype = wtype;
							pcategory = TypeCategory(ptype);
						}
					}
				}

				/* Convert default result clause, if necessary */
				if (c->casetype != ptype)
				{
					if (!c->casetype)
					{

						/*
						 * default clause is NULL, so assign preferred
						 * type from WHEN clauses...