diff --git a/src/sql/src/func.rs b/src/sql/src/func.rs
index 6b98ec72be9ec..24a29e6c327a3 100644
--- a/src/sql/src/func.rs
+++ b/src/sql/src/func.rs
@@ -27,7 +27,7 @@ use crate::ast::{SelectStatement, Statement};
 use crate::catalog::{CatalogType, TypeCategory, TypeReference};
 use crate::names::{self, ResolvedItemName};
 use crate::plan::error::PlanError;
-use crate::plan::expr::{
+use crate::plan::hir::{
     AggregateFunc, BinaryFunc, CoercibleScalarExpr, CoercibleScalarType, ColumnOrder,
     HirRelationExpr, HirScalarExpr, ScalarWindowFunc, TableFunc, UnaryFunc, UnmaterializableFunc,
     ValueWindowFunc, VariadicFunc,
diff --git a/src/sql/src/plan.rs b/src/sql/src/plan.rs
index 7558f5f0110f5..54154a2a6883c 100644
--- a/src/sql/src/plan.rs
+++ b/src/sql/src/plan.rs
@@ -87,7 +87,7 @@ use crate::names::{
 
 pub(crate) mod error;
 pub(crate) mod explain;
-pub(crate) mod expr;
+pub(crate) mod hir;
 pub(crate) mod literal;
 pub(crate) mod lowering;
 pub(crate) mod notice;
@@ -106,7 +106,7 @@ use crate::plan::statement::ddl::ClusterAlterUntilReadyOptionExtracted;
 use crate::plan::with_options::OptionalDuration;
 pub use error::PlanError;
 pub use explain::normalize_subqueries;
-pub use expr::{
+pub use hir::{
     AggregateExpr, CoercibleScalarExpr, Hir, HirRelationExpr, HirScalarExpr, JoinKind,
     WindowExprType,
 };
diff --git a/src/sql/src/plan/expr.rs b/src/sql/src/plan/hir.rs
similarity index 99%
rename from src/sql/src/plan/expr.rs
rename to src/sql/src/plan/hir.rs
index e191855e221e9..687b028f418ee 100644
--- a/src/sql/src/plan/expr.rs
+++ b/src/sql/src/plan/hir.rs
@@ -7,10 +7,9 @@
 // the Business Source License, use of this software will be governed
 // by the Apache License, Version 2.0.
 
-//! This file houses a representation of a SQL plan that is parallel to that found in
-//! src/expr/relation/mod.rs, but represents an earlier phase of planning. It's structurally very
-//! similar to that file, with some differences which are noted below. It gets turned into that
-//! representation via a call to lower().
+//! This file houses HIR, a representation of a SQL plan that is parallel to MIR, but represents
+//! an earlier phase of planning. It's structurally very similar to MIR, with some differences
+//! which are noted below. It gets turned into MIR via a call to lower().
 
 use std::collections::{BTreeMap, BTreeSet};
 use std::fmt::{Display, Formatter};
diff --git a/src/sql/src/plan/lowering.rs b/src/sql/src/plan/lowering.rs
index c4230ce3839fd..8ca869a598805 100644
--- a/src/sql/src/plan/lowering.rs
+++ b/src/sql/src/plan/lowering.rs
@@ -40,7 +40,7 @@ use std::collections::{BTreeMap, BTreeSet};
 use std::iter::repeat;
 
 use crate::optimizer_metrics::OptimizerMetrics;
-use crate::plan::expr::{
+use crate::plan::hir::{
     AggregateExpr, ColumnOrder, ColumnRef, HirRelationExpr, HirScalarExpr, JoinKind, WindowExprType,
 };
 use crate::plan::{transform_hir, PlanError};
diff --git a/src/sql/src/plan/lowering/variadic_left.rs b/src/sql/src/plan/lowering/variadic_left.rs
index 5962654c7e361..2513384f8f12f 100644
--- a/src/sql/src/plan/lowering/variadic_left.rs
+++ b/src/sql/src/plan/lowering/variadic_left.rs
@@ -11,7 +11,7 @@ use itertools::Itertools;
 use mz_expr::{MirRelationExpr, MirScalarExpr};
 use mz_ore::soft_assert_eq_or_log;
 
-use crate::plan::expr::{HirRelationExpr, HirScalarExpr};
+use crate::plan::hir::{HirRelationExpr, HirScalarExpr};
 use crate::plan::lowering::{ColumnMap, Context, CteMap};
 use crate::plan::PlanError;
 
diff --git a/src/sql/src/plan/query.rs b/src/sql/src/plan/query.rs
index d79842eca366a..2778774acf4cb 100644
--- a/src/sql/src/plan/query.rs
+++ b/src/sql/src/plan/query.rs
@@ -82,7 +82,7 @@ use crate::names::{
 };
 use crate::normalize;
 use crate::plan::error::PlanError;
-use crate::plan::expr::{
+use crate::plan::hir::{
     AbstractColumnType, AbstractExpr, AggregateExpr, AggregateFunc, AggregateWindowExpr,
     BinaryFunc, CoercibleScalarExpr, CoercibleScalarType, ColumnOrder, ColumnRef, Hir,
     HirRelationExpr, HirScalarExpr, JoinKind, ScalarWindowExpr, ScalarWindowFunc, UnaryFunc,
diff --git a/src/sql/src/plan/scope.rs b/src/sql/src/plan/scope.rs
index 54cd00839fc74..6e99c0cb91b03 100644
--- a/src/sql/src/plan/scope.rs
+++ b/src/sql/src/plan/scope.rs
@@ -50,7 +50,7 @@ use mz_repr::ColumnName;
 use crate::ast::Expr;
 use crate::names::{Aug, PartialItemName};
 use crate::plan::error::PlanError;
-use crate::plan::expr::ColumnRef;
+use crate::plan::hir::ColumnRef;
 use crate::plan::plan_utils::JoinSide;
 
 #[derive(Debug, Clone)]
diff --git a/src/sql/src/plan/transform_hir.rs b/src/sql/src/plan/transform_hir.rs
index e2f0b8f29f7e7..6545475f18c16 100644
--- a/src/sql/src/plan/transform_hir.rs
+++ b/src/sql/src/plan/transform_hir.rs
@@ -20,7 +20,7 @@ use mz_expr::{ColumnOrder, UnaryFunc, VariadicFunc};
 use mz_ore::stack::RecursionLimitError;
 use mz_repr::{ColumnName, ColumnType, RelationType, ScalarType};
 
-use crate::plan::expr::{
+use crate::plan::hir::{
     AbstractExpr, AggregateFunc, AggregateWindowExpr, ColumnRef, HirRelationExpr, HirScalarExpr,
     ValueWindowExpr, ValueWindowFunc, WindowExpr,
 };
diff --git a/src/sql/src/plan/typeconv.rs b/src/sql/src/plan/typeconv.rs
index 3e7452faf0a45..beba28e26dd35 100644
--- a/src/sql/src/plan/typeconv.rs
+++ b/src/sql/src/plan/typeconv.rs
@@ -23,7 +23,7 @@ use mz_repr::{ColumnName, ColumnType, Datum, RelationType, ScalarBaseType, Scala
 
 use crate::catalog::TypeCategory;
 use crate::plan::error::PlanError;
-use crate::plan::expr::{
+use crate::plan::hir::{
     AbstractColumnType, CoercibleScalarExpr, CoercibleScalarType, ColumnRef, HirScalarExpr,
     UnaryFunc,
 };
diff --git a/src/sql/src/pure/postgres.rs b/src/sql/src/pure/postgres.rs
index 7e467057920bd..27d38bc6ce68d 100644
--- a/src/sql/src/pure/postgres.rs
+++ b/src/sql/src/pure/postgres.rs
@@ -29,7 +29,7 @@ use tokio_postgres::Client;
 
 use crate::names::{Aug, ResolvedItemName};
 use crate::normalize;
-use crate::plan::expr::ColumnRef;
+use crate::plan::hir::ColumnRef;
 use crate::plan::typeconv::{plan_cast, CastContext};
 use crate::plan::{
     ExprContext, HirScalarExpr, PlanError, QueryContext, QueryLifetime, Scope, StatementContext,