diff --git a/crates/rayexec_execution/src/execution/operators_exp/physical_hash_join/build_data.rs b/crates/rayexec_execution/src/execution/operators_exp/physical_hash_join/build_data.rs
new file mode 100644
index 000000000..62ab0eab7
--- /dev/null
+++ b/crates/rayexec_execution/src/execution/operators_exp/physical_hash_join/build_data.rs
@@ -0,0 +1,62 @@
+use rayexec_error::Result;
+
+use crate::arrays::batch::Batch;
+use crate::arrays::buffer_manager::BufferManager;
+use crate::arrays::datatype::DataType;
+use crate::execution::operators_exp::batch_collection::BatchCollectionBlock;
+
+#[derive(Debug)]
+pub struct BuildData<B: BufferManager> {
+    capacity_per_block: usize,
+    blocks: Vec<BuildBlock<B>>,
+}
+
+impl<B> BuildData<B>
+where
+    B: BufferManager,
+{
+    pub fn push_batch(&mut self, manager: &B, input_types: &[DataType], batch: &Batch<B>) -> Result<()> {
+        let mut block = self.pop_or_allocate_block(manager, input_types, batch.num_rows())?;
+
+        // TODO: Hashes
+
+        block.block.append_batch_data(batch)?;
+
+        self.blocks.push(block);
+
+        Ok(())
+    }
+
+    fn pop_or_allocate_block(&mut self, manager: &B, input_types: &[DataType], count: usize) -> Result<BuildBlock<B>> {
+        debug_assert!(count <= self.capacity_per_block);
+
+        if let Some(last) = self.blocks.last() {
+            if last.block.has_capacity_for_rows(count) {
+                return Ok(self.blocks.pop().unwrap());
+            }
+        }
+
+        let block = BuildBlock::new(manager, input_types, self.capacity_per_block)?;
+
+        Ok(block)
+    }
+}
+
+#[derive(Debug)]
+pub struct BuildBlock<B: BufferManager> {
+    block: BatchCollectionBlock<B>,
+    /// Row hashes, allocated to capacity of the batch block.
+    hashes: Vec<u64>,
+}
+
+impl<B> BuildBlock<B>
+where
+    B: BufferManager,
+{
+    pub fn new(manager: &B, input_types: &[DataType], capacity: usize) -> Result<Self> {
+        let block = BatchCollectionBlock::new(manager, input_types, capacity)?;
+        let hashes = vec![0; capacity]; // TODO: Track
+
+        Ok(BuildBlock { block, hashes })
+    }
+}
diff --git a/crates/rayexec_execution/src/execution/operators_exp/physical_hash_join/mod.rs b/crates/rayexec_execution/src/execution/operators_exp/physical_hash_join/mod.rs
new file mode 100644
index 000000000..7e9884380
--- /dev/null
+++ b/crates/rayexec_execution/src/execution/operators_exp/physical_hash_join/mod.rs
@@ -0,0 +1,143 @@
+mod build_data;
+
+use std::task::{Context, Waker};
+
+use build_data::BuildData;
+use parking_lot::Mutex;
+use rayexec_error::{OptionExt, Result};
+
+use super::{
+    ExecutableOperator,
+    ExecuteInOutState,
+    OperatorState,
+    PartitionAndOperatorStates,
+    PartitionState,
+    PollExecute,
+    PollFinalize,
+};
+use crate::arrays::buffer_manager::NopBufferManager;
+use crate::arrays::datatype::DataType;
+use crate::database::DatabaseContext;
+use crate::explain::explainable::{ExplainConfig, ExplainEntry, Explainable};
+
+#[derive(Debug)]
+pub enum HashJoinBuildPartitionState {
+    /// Partition is building.
+    Building(InProgressBuildState),
+    /// Partition finished building.
+    Finished,
+}
+
+#[derive(Debug)]
+pub struct InProgressBuildState {
+    build_data: BuildData<NopBufferManager>,
+}
+
+#[derive(Debug)]
+pub enum HashJoinProbePartitionState {
+    /// Partition waiting for build side to complete.
+    Waiting(usize),
+    /// Partition is probing.
+    Probing(ProbeState),
+    /// Left-join drain state.
+    Draining(DrainState),
+    /// Probing finished.
+    Finished,
+}
+
+#[derive(Debug)]
+pub struct ProbeState {}
+
+#[derive(Debug)]
+pub struct DrainState {}
+
+#[derive(Debug)]
+pub struct HashJoinOperatorState {
+    inner: Mutex<HashJoinOperatorStateInner>,
+}
+
+#[derive(Debug)]
+struct HashJoinOperatorStateInner {
+    /// Wakers from the probe side that are waiting for the build side to
+    /// complete.
+    ///
+    /// Keyed by probe-side partition index.
+    build_waiting_probers: Vec<Option<Waker>>,
+}
+
+#[derive(Debug)]
+pub struct PhysicalHashJoin {
+    /// Data types from the left (build) side of the join.
+    left_types: Vec<DataType>,
+    /// Data types from the right (probe) side of the join.
+    right_types: Vec<DataType>,
+}
+
+impl ExecutableOperator for PhysicalHashJoin {
+    fn create_states(
+        &self,
+        context: &DatabaseContext,
+        batch_size: usize,
+        partitions: usize,
+    ) -> Result<PartitionAndOperatorStates> {
+        unimplemented!()
+    }
+
+    fn poll_execute(
+        &self,
+        cx: &mut Context,
+        partition_state: &mut PartitionState,
+        operator_state: &OperatorState,
+        inout: ExecuteInOutState,
+    ) -> Result<PollExecute> {
+        match partition_state {
+            PartitionState::HashJoinBuild(state) => {
+                let state = match state {
+                    HashJoinBuildPartitionState::Building(state) => state,
+                    HashJoinBuildPartitionState::Finished => return Ok(PollExecute::Exhausted), // TODO: Probably should error instead.
+                };
+
+                let batch = inout.input.required("input batch required")?;
+                state
+                    .build_data
+                    .push_batch(&NopBufferManager, &self.left_types, batch)?;
+
+                Ok(PollExecute::NeedsMore)
+            }
+            PartitionState::HashJoinProbe(state) => {
+                match state {
+                    HashJoinProbePartitionState::Waiting(probe_idx) => {
+                        // Still waiting for build side to complete, just need
+                        // to register a waker.
+
+                        let mut operator_state = match operator_state {
+                            OperatorState::HashJoin(state) => state.inner.lock(),
+                            other => panic!("invalid operator state: {other:?}"),
+                        };
+
+                        operator_state.build_waiting_probers[*probe_idx] = Some(cx.waker().clone());
+
+                        Ok(PollExecute::Pending)
+                    }
+                    _ => unimplemented!(),
+                }
+            }
+            other => panic!("invalid partition state: {other:?}"),
+        }
+    }
+
+    fn poll_finalize(
+        &self,
+        cx: &mut Context,
+        partition_state: &mut PartitionState,
+        operator_state: &OperatorState,
+    ) -> Result<PollFinalize> {
+        unimplemented!()
+    }
+}
+
+impl Explainable for PhysicalHashJoin {
+    fn explain_entry(&self, conf: ExplainConfig) -> ExplainEntry {
+        unimplemented!()
+    }
+}