Function convert_testexpr_mutator

src/backend/optimizer/plan/subselect.c:911–961

}

static Node *
convert_testexpr_mutator(Node *node,
						 convert_testexpr_context *context)
{
	if (node == NULL)
		return NULL;
	if (IsA(node, Param))
	{
		Param	   *param = (Param *) node;

		if (param->paramkind == PARAM_SUBLINK)
		{
			if (param->paramid <= 0 ||
				param->paramid > list_length(context->subst_nodes))
				elog(ERROR, "unexpected PARAM_SUBLINK ID: %d", param->paramid);

			/*
			 * We copy the list item to avoid having doubly-linked
			 * substructure in the modified parse tree.  This is probably
			 * unnecessary when it's a Param, but be safe.
			 */
			return (Node *) copyObject(list_nth(context->subst_nodes,
												param->paramid - 1));
		}
	}
	if (IsA(node, SubLink))
	{
		/*
		 * If we come across a nested SubLink, it is neither necessary nor
		 * correct to recurse into it: any PARAM_SUBLINKs we might find inside
		 * belong to the inner SubLink not the outer. So just return it as-is.
		 *
		 * This reasoning depends on the assumption that nothing will pull
		 * subexpressions into or out of the testexpr field of a SubLink, at
		 * least not without replacing PARAM_SUBLINKs first.  If we did want
		 * to do that we'd need to rethink the parser-output representation
		 * altogether, since currently PARAM_SUBLINKs are only unique per
		 * SubLink not globally across the query.  The whole point of
		 * replacing them with Vars or PARAM_EXEC nodes is to make them
		 * globally unique before they escape from the SubLink's testexpr.
		 *
		 * Note: this can't happen when called during SS_process_sublinks,
		 * because that recursively processes inner SubLinks first.  It can
		 * happen when called from convert_ANY_sublink_to_join, though.
		 */
		return node;
	}
	return expression_tree_mutator(node,
								   convert_testexpr_mutator,
								   (void *) context);
}

/*
 * subplan_is_hashable: can we implement an ANY subplan by hashing?