Function transformJoinOnClause

src/backend/parser/parse_clause.c:507–532

transformJoinOnClause() * Transform the qual conditions for JOIN/ON. * Result is a transformed qualification expression. */

 *	  Result is a transformed qualification expression.
 */
static Node *
transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
{
	Node	   *result;
	List	   *save_namespace;

	/*
	 * The namespace that the join expression should see is just the two
	 * subtrees of the JOIN plus any outer references from upper pstate
	 * levels.  Temporarily set this pstate's namespace accordingly.  (We need
	 * not check for refname conflicts, because transformFromClauseItem()
	 * already did.)  All namespace items are marked visible regardless of
	 * LATERAL state.
	 */
	setNamespaceLateralState(namespace, false, true);

	save_namespace = pstate->p_namespace;
	pstate->p_namespace = namespace;

	result = transformWhereClause(pstate, j->quals,
								  EXPR_KIND_JOIN_ON, "JOIN/ON");

	pstate->p_namespace = save_namespace;

	return result;
}

/*
 * transformTableEntry --- transform a RangeVar (simple relation reference)