You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: add_bogokey.rs
    path of file: ./repos/readyset/readyset-mir/src/rewrite
    
    the code of the file until where you have to start completion: use std::iter;

use nom_sql::Expr;
use readyset_client::ViewPlaceholder;
use readyset_errors::{invariant_eq, ReadySetResult};
use tracing::trace;

use crate::node::node_inner::ProjectExpr;
use crate::node::{MirNode, MirNodeInner};
use crate::query::MirQuery;
use crate::Column;

/// If the given query has a Leaf but doesn't have any keys, create a key for it by adding a new
/// node to the query that projects out a constant literal value (a "bogokey", from "bogus key") and
/// making that the key for the query.
///
/// This pass will also handle ensuring that any topk or paginate nodes in leaf position in such
/// queries have `group_by` columns, by lifting the bogokey project node over those nodes and adding
/// the bogokey to their `group_by`
pub(crate) fn add_bogokey_if_necessary(query: &mut MirQuery<'_>) -> ReadySetResult<()> {
    match &query.leaf_node().inner {
        MirNodeInner::Leaf { keys, .. } if keys.is_empty() => {}
        _ => {
            // Either the query has a Leaf with keys (so no bogokey is necessary) or the query has
            // no Leaf at all (which is the case for eg VIEWs). Either way, we don't need to do
            // anything
            return Ok(());
        }
    }

    // Find the node we're going to insert the bogokey project node above
    //
    // Usually this'll be the first leaf project node, but in the case of topk or paginate with an
    // empty group_by we insert above those instead, since those both happen to need a group_by.
    let mut node_to_insert_above = query.leaf();
    while let Some(parent) = query
        .ancestors(node_to_insert_above)?
        .first()
        .filter(|parent| {
            let inner = &query.get_node(**parent).unwrap().inner;
      
    
    fn query_not_needing_bogokey() {
        let query_name = Relation::from("query_needing_bogokey");
        let mut mir_graph = MirGraph::new();
        let base = mir_graph.add_node(MirNode::new(
            "base".into(),
            MirNodeInner::Base {
                column_specs: vec![ColumnSpecification {
                    column: nom_sql::Column::from("a"),
                    sql_type: SqlType::Int(None),
                    constraints: vec![],
                    comment: None,
                }],
                primary_key: Some([Column::from("a")].into()),
                unique_keys: Default::default(),
            },
        ));
        mir_graph[base].add_owner(query_name.clone());

        let alias_table = mir_graph.add_node(MirNode::new(
            "alias_table".into(),
            MirNodeInner::AliasTable {
                table: "query_needing_bogokey".into(),
            },
        ));
        mir_graph[alias_table].add_owner(query_name.clone());
        mir_graph.add_edge(base, alias_table, 0);

        let leaf = mir_graph.add_node(MirNode::new(
            "leaf".into(),
            MirNodeInner::leaf(
                vec![(
                    Column::named("b").aliased_as_table("unprojected_leaf_key"),
                    ViewPlaceholder::OneToOne(1, BinaryOperator::Equal),
                )],
                IndexType::HashMap,
            ),
        ));
        mir_graph[leaf].add_owner(query_name.clone());
        mir_graph.add_edge(alias_table, leaf, 0);

        let mut query = MirQuery::new(query_name, leaf, &mut mir_graph);

        add_bogokey_if_necessary(&mut query).unwrap();

        match &query.leaf_node_mut().inner {
            MirNodeInner::Leaf { keys, .. } => {
                assert_eq!(
                    keys,
                    &[(
                        Column::named("b").aliased_as_table("unprojected_leaf_key"),
                        ViewPlaceholder::OneToOne(1, BinaryOperator::Equal),
                    )]
                )
            }
            _ => panic!(),
        }
    }