adapter: Add RTR call to the frontend peek sequencing

ggevay · ggevay · commit f0b69ff60a27 · 2025-11-22T16:51:48.000+01:00
diff --git a/src/adapter/src/client.rs b/src/adapter/src/client.rs
@@ -1014,7 +1014,8 @@ impl SessionClient {
                 | Command::CheckConsistency { .. }
                 | Command::Dump { .. }
                 | Command::GetComputeInstanceClient { .. }
-                | Command::GetOracle { .. } => {}
+                | Command::GetOracle { .. }
+                | Command::DetermineRealTimeRecentTimestamp { .. } => {}
             };
             cmd
         });
diff --git a/src/adapter/src/command.rs b/src/adapter/src/command.rs
@@ -11,6 +11,7 @@ use std::collections::{BTreeMap, BTreeSet};
 use std::net::IpAddr;
 use std::pin::Pin;
 use std::sync::Arc;
+use std::time::Duration;
 
 use derivative::Derivative;
 use enum_kinds::EnumKind;
@@ -25,7 +26,7 @@ use mz_persist_client::PersistClient;
 use mz_pgcopy::CopyFormatParams;
 use mz_repr::global_id::TransientIdGen;
 use mz_repr::role_id::RoleId;
-use mz_repr::{CatalogItemId, ColumnIndex, RowIterator};
+use mz_repr::{CatalogItemId, ColumnIndex, GlobalId, RowIterator};
 use mz_sql::ast::{FetchDirection, Raw, Statement};
 use mz_sql::catalog::ObjectType;
 use mz_sql::optimizer_metrics::OptimizerMetrics;
@@ -175,6 +176,12 @@ pub enum Command {
             Result<Arc<dyn TimestampOracle<mz_repr::Timestamp> + Send + Sync>, AdapterError>,
         >,
     },
+
+    DetermineRealTimeRecentTimestamp {
+        source_ids: BTreeSet<GlobalId>,
+        real_time_recency_timeout: Duration,
+        tx: oneshot::Sender<Result<Option<mz_repr::Timestamp>, AdapterError>>,
+    },
 }
 
 impl Command {
@@ -196,7 +203,8 @@ impl Command {
             | Command::CheckConsistency { .. }
             | Command::Dump { .. }
             | Command::GetComputeInstanceClient { .. }
-            | Command::GetOracle { .. } => None,
+            | Command::GetOracle { .. }
+            | Command::DetermineRealTimeRecentTimestamp { .. } => None,
         }
     }
 
@@ -218,7 +226,8 @@ impl Command {
             | Command::CheckConsistency { .. }
             | Command::Dump { .. }
             | Command::GetComputeInstanceClient { .. }
-            | Command::GetOracle { .. } => None,
+            | Command::GetOracle { .. }
+            | Command::DetermineRealTimeRecentTimestamp { .. } => None,
         }
     }
 }
diff --git a/src/adapter/src/coord.rs b/src/adapter/src/coord.rs
@@ -363,6 +363,9 @@ impl Message {
                 Command::AuthenticateVerifySASLProof { .. } => "command-auth_verify_sasl_proof",
                 Command::GetComputeInstanceClient { .. } => "get-compute-instance-client",
                 Command::GetOracle { .. } => "get-oracle",
+                Command::DetermineRealTimeRecentTimestamp { .. } => {
+                    "determine-real-time-recent-timestamp"
+                }
             },
             Message::ControllerReady {
                 controller: ControllerReadiness::Compute,
diff --git a/src/adapter/src/coord/command_handler.rs b/src/adapter/src/coord/command_handler.rs
@@ -285,6 +285,34 @@ impl Coordinator {
                         ));
                     let _ = tx.send(oracle);
                 }
+
+                Command::DetermineRealTimeRecentTimestamp {
+                    source_ids,
+                    real_time_recency_timeout,
+                    tx,
+                } => {
+                    let result = self
+                        .determine_real_time_recent_timestamp(
+                            source_ids.iter().copied(),
+                            real_time_recency_timeout,
+                        )
+                        .await;
+
+                    match result {
+                        Ok(Some(fut)) => {
+                            task::spawn(|| "determine real time recent timestamp", async move {
+                                let result = fut.await.map(Some).map_err(AdapterError::from);
+                                let _ = tx.send(result);
+                            });
+                        }
+                        Ok(None) => {
+                            let _ = tx.send(Ok(None));
+                        }
+                        Err(e) => {
+                            let _ = tx.send(Err(e));
+                        }
+                    }
+                }
             }
         }
         .instrument(debug_span!("handle_command"))
diff --git a/src/adapter/src/coord/sequencer/inner.rs b/src/adapter/src/coord/sequencer/inner.rs
@@ -2524,67 +2524,73 @@ impl Coordinator {
         }
     }
 
+    /// Inner method that performs the actual real-time recency timestamp determination.
+    /// This is called by both the old peek sequencing code (via `determine_real_time_recent_timestamp`)
+    /// and the new command handler for `Command::DetermineRealTimeRecentTimestamp`.
+    pub(crate) async fn determine_real_time_recent_timestamp(
+        &self,
+        source_ids: impl Iterator<Item = GlobalId>,
+        real_time_recency_timeout: Duration,
+    ) -> Result<Option<BoxFuture<'static, Result<Timestamp, StorageError<Timestamp>>>>, AdapterError>
+    {
+        let item_ids = source_ids.map(|gid| self.catalog.resolve_item_id(&gid));
+
+        // Find all dependencies transitively because we need to ensure that
+        // RTR queries determine the timestamp from the sources' (i.e.
+        // storage objects that ingest data from external systems) remap
+        // data. We "cheat" a little bit and filter out any IDs that aren't
+        // user objects because we know they are not a RTR source.
+        let mut to_visit = VecDeque::from_iter(item_ids.filter(CatalogItemId::is_user));
+        // If none of the sources are user objects, we don't need to provide
+        // a RTR timestamp.
+        if to_visit.is_empty() {
+            return Ok(None);
+        }
+
+        let mut timestamp_objects = BTreeSet::new();
+
+        while let Some(id) = to_visit.pop_front() {
+            timestamp_objects.insert(id);
+            to_visit.extend(
+                self.catalog()
+                    .get_entry(&id)
+                    .uses()
+                    .into_iter()
+                    .filter(|id| !timestamp_objects.contains(id) && id.is_user()),
+            );
+        }
+        let timestamp_objects = timestamp_objects
+            .into_iter()
+            .flat_map(|item_id| self.catalog().get_entry(&item_id).global_ids())
+            .collect();
+
+        let r = self
+            .controller
+            .determine_real_time_recent_timestamp(timestamp_objects, real_time_recency_timeout)
+            .await?;
+
+        Ok(Some(r))
+    }
+
     /// Checks to see if the session needs a real time recency timestamp and if so returns
     /// a future that will return the timestamp.
-    pub(super) async fn determine_real_time_recent_timestamp(
+    pub(crate) async fn determine_real_time_recent_timestamp_if_needed(
         &self,
         session: &Session,
-        source_ids: impl Iterator<Item = CatalogItemId>,
+        source_ids: impl Iterator<Item = GlobalId>,
     ) -> Result<Option<BoxFuture<'static, Result<Timestamp, StorageError<Timestamp>>>>, AdapterError>
     {
         let vars = session.vars();
 
-        // Ideally this logic belongs inside of
-        // `mz-adapter::coord::timestamp_selection::determine_timestamp`. However, including the
-        // logic in there would make it extremely difficult and inconvenient to pull the waiting off
-        // of the main coord thread.
-        let r = if vars.real_time_recency()
+        if vars.real_time_recency()
             && vars.transaction_isolation() == &IsolationLevel::StrictSerializable
             && !session.contains_read_timestamp()
         {
-            // Find all dependencies transitively because we need to ensure that
-            // RTR queries determine the timestamp from the sources' (i.e.
-            // storage objects that ingest data from external systems) remap
-            // data. We "cheat" a little bit and filter out any IDs that aren't
-            // user objects because we know they are not a RTR source.
-            let mut to_visit = VecDeque::from_iter(source_ids.filter(CatalogItemId::is_user));
-            // If none of the sources are user objects, we don't need to provide
-            // a RTR timestamp.
-            if to_visit.is_empty() {
-                return Ok(None);
-            }
-
-            let mut timestamp_objects = BTreeSet::new();
-
-            while let Some(id) = to_visit.pop_front() {
-                timestamp_objects.insert(id);
-                to_visit.extend(
-                    self.catalog()
-                        .get_entry(&id)
-                        .uses()
-                        .into_iter()
-                        .filter(|id| !timestamp_objects.contains(id) && id.is_user()),
-                );
-            }
-            let timestamp_objects = timestamp_objects
-                .into_iter()
-                .flat_map(|item_id| self.catalog().get_entry(&item_id).global_ids())
-                .collect();
-
-            let r = self
-                .controller
-                .determine_real_time_recent_timestamp(
-                    timestamp_objects,
-                    *vars.real_time_recency_timeout(),
-                )
-                .await?;
-
-            Some(r)
+            self.determine_real_time_recent_timestamp(source_ids, *vars.real_time_recency_timeout())
+                .await
         } else {
-            None
-        };
-
-        Ok(r)
+            Ok(None)
+        }
     }
 
     #[instrument]
diff --git a/src/adapter/src/coord/sequencer/inner/explain_timestamp.rs b/src/adapter/src/coord/sequencer/inner/explain_timestamp.rs
@@ -173,12 +173,8 @@ impl Coordinator {
         }: ExplainTimestampRealTimeRecency,
     ) -> Result<StageResult<Box<ExplainTimestampStage>>, AdapterError> {
         let source_ids = optimized_plan.depends_on();
-        let source_items: Vec<_> = source_ids
-            .iter()
-            .map(|gid| self.catalog().resolve_item_id(gid))
-            .collect();
         let fut = self
-            .determine_real_time_recent_timestamp(session, source_items.into_iter())
+            .determine_real_time_recent_timestamp_if_needed(session, source_ids.iter().copied())
             .await?;
 
         match fut {
diff --git a/src/adapter/src/coord/sequencer/inner/peek.rs b/src/adapter/src/coord/sequencer/inner/peek.rs
@@ -756,12 +756,8 @@ impl Coordinator {
             explain_ctx,
         }: PeekStageRealTimeRecency,
     ) -> Result<StageResult<Box<PeekStage>>, AdapterError> {
-        let item_ids: Vec<_> = source_ids
-            .iter()
-            .map(|gid| self.catalog.resolve_item_id(gid))
-            .collect();
         let fut = self
-            .determine_real_time_recent_timestamp(session, item_ids.into_iter())
+            .determine_real_time_recent_timestamp_if_needed(session, source_ids.iter().copied())
             .await?;
 
         match fut {
diff --git a/src/adapter/src/frontend_peek.rs b/src/adapter/src/frontend_peek.rs
@@ -28,6 +28,7 @@ use tracing::{Span, debug};
 use tracing_opentelemetry::OpenTelemetrySpanExt;
 
 use crate::catalog::CatalogState;
+use crate::command::Command;
 use crate::coord::peek::PeekPlan;
 use crate::coord::timestamp_selection::TimestampDetermination;
 use crate::coord::{Coordinator, ExplainContext, TargetCluster};
@@ -286,17 +287,21 @@ impl PeekClient {
 
         // # From peek_real_time_recency
 
-        // TODO(peek-seq): Real-time recency is slow anyhow, so we don't handle it in frontend peek
-        // sequencing for now.
         let vars = session.vars();
-        if vars.real_time_recency()
+        let real_time_recency_ts: Option<Timestamp> = if vars.real_time_recency()
             && vars.transaction_isolation() == &IsolationLevel::StrictSerializable
             && !session.contains_read_timestamp()
         {
-            debug!("Bailing out from try_frontend_peek_inner, because of real time recency");
-            return Ok(None);
-        }
-        let real_time_recency_ts: Option<mz_repr::Timestamp> = None;
+            // Only call the coordinator when we actually need real-time recency
+            self.call_coordinator(|tx| Command::DetermineRealTimeRecentTimestamp {
+                source_ids: source_ids.clone(),
+                real_time_recency_timeout: *vars.real_time_recency_timeout(),
+                tx,
+            })
+            .await?
+        } else {
+            None
+        };
 
         // # From peek_timestamp_read_hold
 
diff --git a/src/adapter/src/peek_client.rs b/src/adapter/src/peek_client.rs
@@ -132,7 +132,7 @@ impl PeekClient {
         catalog
     }
 
-    async fn call_coordinator<T, F>(&self, f: F) -> T
+    pub(crate) async fn call_coordinator<T, F>(&self, f: F) -> T
     where
         F: FnOnce(oneshot::Sender<T>) -> Command,
     {
diff --git a/test/sqllogictest/transactions.slt b/test/sqllogictest/transactions.slt
@@ -689,6 +689,10 @@ ALTER SYSTEM SET allow_real_time_recency = true
 ----
 COMPLETE 0
 
+# TODO(ggevay): I think this is not actually testing real-time recency, because tables don't participate in the
+# RTR machinery at all. (We do get the latest contents of a table in STRICT SERIALIZABLE mode even without RTR
+# being turned on.) We do have other tests in Testdrive, though.
+
 statement ok
 SET REAL_TIME_RECENCY TO TRUE
 

Original file line number	Diff line number	Diff line change
`@@ -132,7 +132,7 @@ impl PeekClient {`
`132`	`132`	`catalog`
`133`	`133`	`}`
`134`	`134`
`135`		`- async fn call_coordinator<T, F>(&self, f: F) -> T`
	`135`	`+ pub(crate) async fn call_coordinator<T, F>(&self, f: F) -> T`
`136`	`136`	`where`
`137`	`137`	`F: FnOnce(oneshot::Sender<T>) -> Command,`
`138`	`138`	`{`