Function initialize_mergeclause_eclasses

src/backend/optimizer/path/pathkeys.c:1782–1819

* initialize_mergeclause_eclasses * Set the EquivalenceClass links in a mergeclause restrictinfo. * * RestrictInfo contains fields in which we may cache pointers to * EquivalenceClasses for the left and right inputs of the mergeclause. * (If the mergeclause is a true equivalence clause these will be the * same EquivalenceClass, otherwise not.) If the mergeclause is either * used to genera

 * they've been updated to point to canonical ECs.
 */
void
initialize_mergeclause_eclasses(PlannerInfo *root, RestrictInfo *restrictinfo)
{
	Expr	   *clause = restrictinfo->clause;
	Oid			lefttype,
				righttype;

	/* Should be a mergeclause ... */
	Assert(restrictinfo->mergeopfamilies != NIL);
	/* ... with links not yet set */
	Assert(restrictinfo->left_ec == NULL);
	Assert(restrictinfo->right_ec == NULL);

	/* Need the declared input types of the operator */
	op_input_types(((OpExpr *) clause)->opno, &lefttype, &righttype);

	/* Find or create a matching EquivalenceClass for each side */
	restrictinfo->left_ec =
		get_eclass_for_sort_expr(root,
								 (Expr *) get_leftop(clause),
								 restrictinfo->nullable_relids,
								 restrictinfo->mergeopfamilies,
								 lefttype,
								 ((OpExpr *) clause)->inputcollid,
								 0,
								 NULL,
								 true);
	restrictinfo->right_ec =
		get_eclass_for_sort_expr(root,
								 (Expr *) get_rightop(clause),
								 restrictinfo->nullable_relids,
								 restrictinfo->mergeopfamilies,
								 righttype,
								 ((OpExpr *) clause)->inputcollid,
								 0,
								 NULL,
								 true);
}

/*
 * update_mergeclause_eclasses