parse_target.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 672 行 · 第 1/2 页

	 * If the expression is a DEFAULT placeholder, insert the attribute's
	 * type/typmod into it so that exprType will report the right things.
	 * (We expect that the eventually substituted default expression will
	 * in fact have this type and typmod.)	Also, reject trying to update
	 * an array element with DEFAULT, since there can't be any default for
	 * individual elements of a column.
	 */
	if (tle->expr && IsA(tle->expr, SetToDefault))
	{
		SetToDefault *def = (SetToDefault *) tle->expr;

		def->typeId = attrtype;
		def->typeMod = attrtypmod;
		if (indirection)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot set an array element to DEFAULT")));
	}

	/* Now we can use exprType() safely. */
	type_id = exprType((Node *) tle->expr);

	/*
	 * If there are subscripts on the target column, prepare an array
	 * assignment expression.  This will generate an array value that the
	 * source value has been inserted into, which can then be placed in
	 * the new tuple constructed by INSERT or UPDATE. Note that
	 * transformArraySubscripts takes care of type coercion.
	 */
	if (indirection)
	{
		Node	   *arrayBase;
		ArrayRef   *aref;

		if (pstate->p_is_insert)
		{
			/*
			 * The command is INSERT INTO table (arraycol[subscripts]) ...
			 * so there is not really a source array value to work with.
			 * Let the executor do something reasonable, if it can. Notice
			 * that we force transformArraySubscripts to treat the
			 * subscripting op as an array-slice op below, so the source
			 * data will have been coerced to the array type.
			 */
			arrayBase = NULL;	/* signal there is no source array */
		}
		else
		{
			/*
			 * Build a Var for the array to be updated.
			 */
			arrayBase = (Node *) make_var(pstate,
										  pstate->p_target_rangetblentry,
										  attrno);
		}

		aref = transformArraySubscripts(pstate,
										arrayBase,
										attrtype,
										attrtypmod,
										indirection,
										pstate->p_is_insert,
										(Node *) tle->expr);
		tle->expr = (Expr *) aref;
	}
	else
	{
		/*
		 * For normal non-subscripted target column, do type checking and
		 * coercion.  But accept InvalidOid, which indicates the source is
		 * a NULL constant.  (XXX is that still true?)
		 */
		if (type_id != InvalidOid)
		{
			tle->expr = (Expr *)
				coerce_to_target_type(pstate,
									  (Node *) tle->expr, type_id,
									  attrtype, attrtypmod,
									  COERCION_ASSIGNMENT,
									  COERCE_IMPLICIT_CAST);
			if (tle->expr == NULL)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("column \"%s\" is of type %s"
								" but expression is of type %s",
								colname,
								format_type_be(attrtype),
								format_type_be(type_id)),
						 errhint("You will need to rewrite or cast the expression.")));
		}
	}

	/*
	 * The result of the target expression should now match the
	 * destination column's type.
	 */
	resnode->restype = attrtype;
	resnode->restypmod = attrtypmod;
	/*
	 * Set the resno to identify the target column --- the rewriter and
	 * planner depend on this.  We also set the resname to identify the
	 * target column, but this is only for debugging purposes; it should
	 * not be relied on.  (In particular, it might be out of date in a
	 * stored rule.)
	 */
	resnode->resno = (AttrNumber) attrno;
	resnode->resname = colname;
}


/*
 * checkInsertTargets -
 *	  generate a list of INSERT column targets if not supplied, or
 *	  test supplied column names to make sure they are in target table.
 *	  Also return an integer list of the columns' attribute numbers.
 */
List *
checkInsertTargets(ParseState *pstate, List *cols, List **attrnos)
{
	*attrnos = NIL;

	if (cols == NIL)
	{
		/*
		 * Generate default column list for INSERT.
		 */
		Form_pg_attribute *attr = pstate->p_target_relation->rd_att->attrs;
		int			numcol = pstate->p_target_relation->rd_rel->relnatts;
		int			i;

		for (i = 0; i < numcol; i++)
		{
			ResTarget  *col;

			if (attr[i]->attisdropped)
				continue;

			col = makeNode(ResTarget);
			col->name = pstrdup(NameStr(attr[i]->attname));
			col->indirection = NIL;
			col->val = NULL;
			cols = lappend(cols, col);
			*attrnos = lappendi(*attrnos, i + 1);
		}
	}
	else
	{
		/*
		 * Do initial validation of user-supplied INSERT column list.
		 */
		List	   *tl;

		foreach(tl, cols)
		{
			char	   *name = ((ResTarget *) lfirst(tl))->name;
			int			attrno;

			/* Lookup column name, ereport on failure */
			attrno = attnameAttNum(pstate->p_target_relation, name, false);
			/* Check for duplicates */
			if (intMember(attrno, *attrnos))
				ereport(ERROR,
						(errcode(ERRCODE_DUPLICATE_COLUMN),
					  errmsg("column \"%s\" specified more than once",
							 name)));
			*attrnos = lappendi(*attrnos, attrno);
		}
	}

	return cols;
}

/* ExpandAllTables()
 * Turns '*' (in the target list) into a list of targetlist entries.
 *
 * tlist entries are generated for each relation appearing at the top level
 * of the query's namespace, except for RTEs marked not inFromCl.  (These
 * may include NEW/OLD pseudo-entries, implicit RTEs, etc.)
 */
static List *
ExpandAllTables(ParseState *pstate)
{
	List	   *target = NIL;
	bool		found_table = false;
	List	   *ns;

	foreach(ns, pstate->p_namespace)
	{
		Node	   *n = (Node *) lfirst(ns);
		RangeTblEntry *rte;

		if (IsA(n, RangeTblRef))
			rte = rt_fetch(((RangeTblRef *) n)->rtindex,
						   pstate->p_rtable);
		else if (IsA(n, JoinExpr))
			rte = rt_fetch(((JoinExpr *) n)->rtindex,
						   pstate->p_rtable);
		else
		{
			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
			rte = NULL;			/* keep compiler quiet */
		}

		/*
		 * Ignore added-on relations that were not listed in the FROM
		 * clause.
		 */
		if (!rte->inFromCl)
			continue;

		found_table = true;
		target = nconc(target, expandRelAttrs(pstate, rte));
	}

	/* Check for SELECT *; */
	if (!found_table)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
			  errmsg("SELECT * with no tables specified is not valid")));

	return target;
}

/*
 * FigureColname -
 *	  if the name of the resulting column is not specified in the target
 *	  list, we have to guess a suitable name.  The SQL spec provides some
 *	  guidance, but not much...
 *
 * Note that the argument is the *untransformed* parse tree for the target
 * item.  This is a shade easier to work with than the transformed tree.
 */
static char *
FigureColname(Node *node)
{
	char	   *name = NULL;

	FigureColnameInternal(node, &name);
	if (name != NULL)
		return name;
	/* default result if we can't guess anything */
	return "?column?";
}

static int
FigureColnameInternal(Node *node, char **name)
{
	int			strength = 0;

	if (node == NULL)
		return strength;

	switch (nodeTag(node))
	{
		case T_ColumnRef:
			{
				char	   *cname = strVal(llast(((ColumnRef *) node)->fields));

				if (strcmp(cname, "*") != 0)
				{
					*name = cname;
					return 2;
				}
			}
			break;
		case T_ExprFieldSelect:
			{
				ExprFieldSelect *efs = (ExprFieldSelect *) node;

				if (efs->fields)
				{
					char	   *fname = strVal(llast(efs->fields));

					if (strcmp(fname, "*") != 0)
					{
						*name = fname;
						return 2;
					}
				}
				return FigureColnameInternal(efs->arg, name);
			}
			break;
		case T_FuncCall:
			*name = strVal(llast(((FuncCall *) node)->funcname));
			return 2;
		case T_A_Expr:
			/* make nullif() act like a regular function */
			if (((A_Expr *) node)->kind == AEXPR_NULLIF)
			{
				*name = "nullif";
				return 2;
			}
			break;
		case T_A_Const:
			if (((A_Const *) node)->typename != NULL)
			{
				*name = strVal(llast(((A_Const *) node)->typename->names));
				return 1;
			}
			break;
		case T_TypeCast:
			strength = FigureColnameInternal(((TypeCast *) node)->arg,
											 name);
			if (strength <= 1)
			{
				if (((TypeCast *) node)->typename != NULL)
				{
					*name = strVal(llast(((TypeCast *) node)->typename->names));
					return 1;
				}
			}
			break;
		case T_CaseExpr:
			strength = FigureColnameInternal((Node *) ((CaseExpr *) node)->defresult,
											 name);
			if (strength <= 1)
			{
				*name = "case";
				return 1;
			}
			break;
		case T_ArrayExpr:
			/* make ARRAY[] act like a function */
			*name = "array";
			return 2;
		case T_CoalesceExpr:
			/* make coalesce() act like a regular function */
			*name = "coalesce";
			return 2;
		default:
			break;
	}

	return strength;
}