parse_clause.c

来自「PostgreSQL7.4.6 for Linux」· C语言 代码 · 共 1,591 行 · 第 1/3 页

	 */
	rtr = makeNode(RangeTblRef);
	/* assume new rte is at end */
	rtr->rtindex = length(pstate->p_rtable);
	Assert(rte == rt_fetch(rtr->rtindex, pstate->p_rtable));

	return rtr;
}


/*
 * transformFromClauseItem -
 *	  Transform a FROM-clause item, adding any required entries to the
 *	  range table list being built in the ParseState, and return the
 *	  transformed item ready to include in the joinlist and namespace.
 *	  This routine can recurse to handle SQL92 JOIN expressions.
 *
 *	  Aside from the primary return value (the transformed joinlist item)
 *	  this routine also returns an integer list of the rangetable indexes
 *	  of all the base and join relations represented in the joinlist item.
 *	  This list is needed for checking JOIN/ON conditions in higher levels.
 */
static Node *
transformFromClauseItem(ParseState *pstate, Node *n, List **containedRels)
{
	if (IsA(n, RangeVar))
	{
		/* Plain relation reference */
		RangeTblRef *rtr;

		rtr = transformTableEntry(pstate, (RangeVar *) n);
		*containedRels = makeListi1(rtr->rtindex);
		return (Node *) rtr;
	}
	else if (IsA(n, RangeSubselect))
	{
		/* sub-SELECT is like a plain relation */
		RangeTblRef *rtr;

		rtr = transformRangeSubselect(pstate, (RangeSubselect *) n);
		*containedRels = makeListi1(rtr->rtindex);
		return (Node *) rtr;
	}
	else if (IsA(n, RangeFunction))
	{
		/* function is like a plain relation */
		RangeTblRef *rtr;

		rtr = transformRangeFunction(pstate, (RangeFunction *) n);
		*containedRels = makeListi1(rtr->rtindex);
		return (Node *) rtr;
	}
	else if (IsA(n, JoinExpr))
	{
		/* A newfangled join expression */
		JoinExpr   *j = (JoinExpr *) n;
		List	   *my_containedRels,
				   *l_containedRels,
				   *r_containedRels,
				   *l_colnames,
				   *r_colnames,
				   *res_colnames,
				   *l_colvars,
				   *r_colvars,
				   *res_colvars;
		Index		leftrti,
					rightrti;
		RangeTblEntry *rte;

		/*
		 * Recursively process the left and right subtrees
		 */
		j->larg = transformFromClauseItem(pstate, j->larg, &l_containedRels);
		j->rarg = transformFromClauseItem(pstate, j->rarg, &r_containedRels);

		/*
		 * Generate combined list of relation indexes for possible use by
		 * transformJoinOnClause below.
		 */
		my_containedRels = nconc(l_containedRels, r_containedRels);

		/*
		 * Check for conflicting refnames in left and right subtrees. Must
		 * do this because higher levels will assume I hand back a self-
		 * consistent namespace subtree.
		 */
		checkNameSpaceConflicts(pstate, j->larg, j->rarg);

		/*
		 * Extract column name and var lists from both subtrees
		 *
		 * Note: expandRTE returns new lists, safe for me to modify
		 */
		if (IsA(j->larg, RangeTblRef))
			leftrti = ((RangeTblRef *) j->larg)->rtindex;
		else if (IsA(j->larg, JoinExpr))
			leftrti = ((JoinExpr *) j->larg)->rtindex;
		else
		{
			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(j->larg));
			leftrti = 0;		/* keep compiler quiet */
		}
		rte = rt_fetch(leftrti, pstate->p_rtable);
		expandRTE(pstate, rte, &l_colnames, &l_colvars);

		if (IsA(j->rarg, RangeTblRef))
			rightrti = ((RangeTblRef *) j->rarg)->rtindex;
		else if (IsA(j->rarg, JoinExpr))
			rightrti = ((JoinExpr *) j->rarg)->rtindex;
		else
		{
			elog(ERROR, "unrecognized node type: %d", (int) nodeTag(j->rarg));
			rightrti = 0;		/* keep compiler quiet */
		}
		rte = rt_fetch(rightrti, pstate->p_rtable);
		expandRTE(pstate, rte, &r_colnames, &r_colvars);

		/*
		 * Natural join does not explicitly specify columns; must generate
		 * columns to join. Need to run through the list of columns from
		 * each table or join result and match up the column names. Use
		 * the first table, and check every column in the second table for
		 * a match.  (We'll check that the matches were unique later on.)
		 * The result of this step is a list of column names just like an
		 * explicitly-written USING list.
		 */
		if (j->isNatural)
		{
			List	   *rlist = NIL;
			List	   *lx,
					   *rx;

			Assert(j->using == NIL);	/* shouldn't have USING() too */

			foreach(lx, l_colnames)
			{
				char	   *l_colname = strVal(lfirst(lx));
				Value	   *m_name = NULL;

				foreach(rx, r_colnames)
				{
					char	   *r_colname = strVal(lfirst(rx));

					if (strcmp(l_colname, r_colname) == 0)
					{
						m_name = makeString(l_colname);
						break;
					}
				}

				/* matched a right column? then keep as join column... */
				if (m_name != NULL)
					rlist = lappend(rlist, m_name);
			}

			j->using = rlist;
		}

		/*
		 * Now transform the join qualifications, if any.
		 */
		res_colnames = NIL;
		res_colvars = NIL;

		if (j->using)
		{
			/*
			 * JOIN/USING (or NATURAL JOIN, as transformed above).
			 * Transform the list into an explicit ON-condition, and
			 * generate a list of merged result columns.
			 */
			List	   *ucols = j->using;
			List	   *l_usingvars = NIL;
			List	   *r_usingvars = NIL;
			List	   *ucol;

			Assert(j->quals == NULL);	/* shouldn't have ON() too */

			foreach(ucol, ucols)
			{
				char	   *u_colname = strVal(lfirst(ucol));
				List	   *col;
				int			ndx;
				int			l_index = -1;
				int			r_index = -1;
				Var		   *l_colvar,
						   *r_colvar;

				/* Check for USING(foo,foo) */
				foreach(col, res_colnames)
				{
					char	   *res_colname = strVal(lfirst(col));

					if (strcmp(res_colname, u_colname) == 0)
						ereport(ERROR,
								(errcode(ERRCODE_DUPLICATE_COLUMN),
								 errmsg("column name \"%s\" appears more than once in USING clause",
										u_colname)));
				}

				/* Find it in left input */
				ndx = 0;
				foreach(col, l_colnames)
				{
					char	   *l_colname = strVal(lfirst(col));

					if (strcmp(l_colname, u_colname) == 0)
					{
						if (l_index >= 0)
							ereport(ERROR,
									(errcode(ERRCODE_AMBIGUOUS_COLUMN),
									 errmsg("common column name \"%s\" appears more than once in left table",
											u_colname)));
						l_index = ndx;
					}
					ndx++;
				}
				if (l_index < 0)
					ereport(ERROR,
							(errcode(ERRCODE_UNDEFINED_COLUMN),
							 errmsg("column \"%s\" specified in USING clause does not exist in left table",
									u_colname)));

				/* Find it in right input */
				ndx = 0;
				foreach(col, r_colnames)
				{
					char	   *r_colname = strVal(lfirst(col));

					if (strcmp(r_colname, u_colname) == 0)
					{
						if (r_index >= 0)
							ereport(ERROR,
									(errcode(ERRCODE_AMBIGUOUS_COLUMN),
									 errmsg("common column name \"%s\" appears more than once in right table",
											u_colname)));
						r_index = ndx;
					}
					ndx++;
				}
				if (r_index < 0)
					ereport(ERROR,
							(errcode(ERRCODE_UNDEFINED_COLUMN),
							 errmsg("column \"%s\" specified in USING clause does not exist in right table",
									u_colname)));

				l_colvar = nth(l_index, l_colvars);
				l_usingvars = lappend(l_usingvars, l_colvar);
				r_colvar = nth(r_index, r_colvars);
				r_usingvars = lappend(r_usingvars, r_colvar);

				res_colnames = lappend(res_colnames, lfirst(ucol));
				res_colvars = lappend(res_colvars,
									  buildMergedJoinVar(pstate,
														 j->jointype,
														 l_colvar,
														 r_colvar));
			}

			j->quals = transformJoinUsingClause(pstate,
												l_usingvars,
												r_usingvars);
		}
		else if (j->quals)
		{
			/* User-written ON-condition; transform it */
			j->quals = transformJoinOnClause(pstate, j, my_containedRels);
		}
		else
		{
			/* CROSS JOIN: no quals */
		}

		/* Add remaining columns from each side to the output columns */
		extractRemainingColumns(res_colnames,
								l_colnames, l_colvars,
								&l_colnames, &l_colvars);
		extractRemainingColumns(res_colnames,
								r_colnames, r_colvars,
								&r_colnames, &r_colvars);
		res_colnames = nconc(res_colnames, l_colnames);
		res_colvars = nconc(res_colvars, l_colvars);
		res_colnames = nconc(res_colnames, r_colnames);
		res_colvars = nconc(res_colvars, r_colvars);

		/*
		 * Check alias (AS clause), if any.
		 */
		if (j->alias)
		{
			if (j->alias->colnames != NIL)
			{
				if (length(j->alias->colnames) > length(res_colnames))
					ereport(ERROR,
							(errcode(ERRCODE_SYNTAX_ERROR),
							 errmsg("column alias list for \"%s\" has too many entries",
									j->alias->aliasname)));
			}
		}

		/*
		 * Now build an RTE for the result of the join
		 */
		rte = addRangeTableEntryForJoin(pstate,
										res_colnames,
										j->jointype,
										res_colvars,
										j->alias,
										true);

		/* assume new rte is at end */
		j->rtindex = length(pstate->p_rtable);
		Assert(rte == rt_fetch(j->rtindex, pstate->p_rtable));

		/*
		 * Include join RTE in returned containedRels list
		 */
		*containedRels = lconsi(j->rtindex, my_containedRels);

		return (Node *) j;
	}
	else
		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
	return NULL;				/* can't get here, keep compiler quiet */
}

/*
 * buildMergedJoinVar -
 *	  generate a suitable replacement expression for a merged join column
 */
static Node *
buildMergedJoinVar(ParseState *pstate, JoinType jointype,
				   Var *l_colvar, Var *r_colvar)
{
	Oid			outcoltype;
	int32		outcoltypmod;
	Node	   *l_node,
			   *r_node,
			   *res_node;

	/*
	 * Choose output type if input types are dissimilar.
	 */
	outcoltype = l_colvar->vartype;
	outcoltypmod = l_colvar->vartypmod;
	if (outcoltype != r_colvar->vartype)
	{
		outcoltype = select_common_type(makeListo2(l_colvar->vartype,
												   r_colvar->vartype),
										"JOIN/USING");
		outcoltypmod = -1;		/* ie, unknown */
	}
	else if (outcoltypmod != r_colvar->vartypmod)
	{
		/* same type, but not same typmod */
		outcoltypmod = -1;		/* ie, unknown */
	}

	/*
	 * Insert coercion functions if needed.  Note that a difference in
	 * typmod can only happen if input has typmod but outcoltypmod is -1.
	 * In that case we insert a RelabelType to clearly mark that result's
	 * typmod is not same as input.
	 */
	if (l_colvar->vartype != outcoltype)
		l_node = coerce_type(pstate, (Node *) l_colvar, l_colvar->vartype,
							 outcoltype,
							 COERCION_IMPLICIT, COERCE_IMPLICIT_CAST);
	else if (l_colvar->vartypmod != outcoltypmod)
		l_node = (Node *) makeRelabelType((Expr *) l_colvar,
										  outcoltype, outcoltypmod,
										  COERCE_IMPLICIT_CAST);
	else
		l_node = (Node *) l_colvar;

	if (r_colvar->vartype != outcoltype)
		r_node = coerce_type(pstate, (Node *) r_colvar, r_colvar->vartype,
							 outcoltype,
							 COERCION_IMPLICIT, COERCE_IMPLICIT_CAST);
	else if (r_colvar->vartypmod != outcoltypmod)
		r_node = (Node *) makeRelabelType((Expr *) r_colvar,
										  outcoltype, outcoltypmod,
										  COERCE_IMPLICIT_CAST);
	else
		r_node = (Node *) r_colvar;

	/*
	 * Choose what to emit
	 */
	switch (jointype)
	{
		case JOIN_INNER:

			/*
			 * We can use either var; prefer non-coerced one if available.
			 */
			if (IsA(l_node, Var))
				res_node = l_node;
			else if (IsA(r_node, Var))
				res_node = r_node;
			else
				res_node = l_node;
			break;
		case JOIN_LEFT:
			/* Always use left var */
			res_node = l_node;
			break;
		case JOIN_RIGHT:
			/* Always use right var */
			res_node = r_node;
			break;
		case JOIN_FULL:
			{
				/*
				 * Here we must build a COALESCE expression to ensure that
				 * the join output is non-null if either input is.
				 */
				CoalesceExpr *c = makeNode(CoalesceExpr);

				c->coalescetype = outcoltype;
				c->args = makeList2(l_node, r_node);
				res_node = (Node *) c;
				break;
			}
		default:
			elog(ERROR, "unrecognized join type: %d", (int) jointype);
			res_node = NULL;	/* keep compiler quiet */
			break;
	}

	return res_node;
}


/*
 * transformWhereClause -
 *	  Transform the qualification and make sure it is of type boolean.
 *	  Used for WHERE and allied clauses.
 *
 * constructName does not affect the semantics, but is used in error messages
 */
Node *
transformWhereClause(ParseState *pstate, Node *clause,
					 const char *constructName)
{
	Node	   *qual;

	if (clause == NULL)
		return NULL;

	qual = transformExpr(pstate, clause);

	qual = coerce_to_boolean(pstate, qual, constructName);

	return qual;
}


/*
 * transformLimitClause -
 *	  Transform the expression and make sure it is of type integer.
 *	  Used for LIMIT and allied clauses.
 *
 * constructName does not affect the semantics, but is used in error messages
 */
Node *
transformLimitClause(ParseState *pstate, Node *clause,
					 const char *constructName)
{
	Node	   *qual;

	if (clause == NULL)
		return NULL;

	qual = transformExpr(pstate, clause);

	qual = coerce_to_integer(pstate, qual, constructName);

	/*
	 * LIMIT can't refer to any vars or aggregates of the current query;
	 * we don't allow subselects either (though that case would at least
	 * be sensible)
	 */
	if (contain_vars_of_level(qual, 0))
	{
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
		/* translator: %s is name of a SQL construct, eg LIMIT */
				 errmsg("argument of %s must not contain variables",
						constructName)));
	}
	if (checkExprHasAggs(qual))
	{
		ereport(ERROR,
				(errcode(ERRCODE_GROUPING_ERROR),
		/* translator: %s is name of a SQL construct, eg LIMIT */
				 errmsg("argument of %s must not contain aggregates",
						constructName)));
	}
	if (contain_subplans(qual))
	{
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
		/* translator: %s is name of a SQL construct, eg LIMIT */
				 errmsg("argument of %s must not contain subqueries",
						constructName)));
	}

	return qual;
}


/*
 *	findTargetlistEntry -
 *	  Returns the targetlist entry matching the given (untransformed) node.
 *	  If no matching entry exists, one is created and appended to the target
 *	  list as a "resjunk" node.
 *
 * node		the ORDER BY, GROUP BY, or DISTINCT ON expression to be matched
 * tlist	the existing target list (NB: this will never be NIL, which is a
 *			good thing since we'd be unable to append to it if it were...)
 * clause	identifies clause type being processed.
 */
static TargetEntry *
findTargetlistEntry(ParseState *pstate, Node *node, List *tlist, int clause)
{
	TargetEntry *target_result = NULL;
	List	   *tl;
	Node	   *expr;

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