feat: add rowset planning and pruning

src/inmem/immutable/memtable.rs

@@ -128,6 +128,10 @@ impl ImmutableMemTable {
         ImmutableRowIter::new(self)
     }
 
+    pub(crate) fn entry_count(&self) -> usize {
+        self.index.len()
+    }
+
     pub(crate) fn min_key(&self) -> Option<KeyOwned> {
         self.index.keys().next().map(|view| view.key().to_owned())
     }
@@ -143,6 +147,22 @@ impl ImmutableMemTable {
         &self.mvcc
     }
 
+    pub(crate) fn commit_ts_bounds(&self) -> Option<(Timestamp, Timestamp)> {
+        let mut iter = self.mvcc.commit_ts.iter();
+        let first = iter.next()?;
+        let mut min_ts = *first;
+        let mut max_ts = *first;
+        for ts in iter {
+            if *ts < min_ts {
+                min_ts = *ts;
+            }
+            if *ts > max_ts {
+                max_ts = *ts;
+            }
+        }
+        Some((min_ts, max_ts))
+    }
+
     fn mvcc_row(&self, row: u32) -> (Timestamp, bool) {
         let idx = row as usize;
         (self.mvcc.commit_ts[idx], self.mvcc.tombstone[idx])

src/inmem/immutable/mod.rs

@@ -8,6 +8,32 @@ pub(crate) mod memtable;
 pub(crate) type ImmutableSegment = memtable::ImmutableMemTable;
 
 /// Lightweight pruning helper; currently returns all segment indexes.
-pub(crate) fn prune_segments(segments: &[&ImmutableSegment]) -> Vec<usize> {
-    (0..segments.len()).collect()
+pub(crate) fn prune_segments(
+    segments: &[&ImmutableSegment],
+    key_bounds: Option<&crate::query::scan::KeyBounds>,
+    read_ts: crate::mvcc::Timestamp,
+) -> Vec<usize> {
+    segments
+        .iter()
+        .enumerate()
+        .filter_map(|(idx, segment)| {
+            if segment.entry_count() == 0 {
+                return None;
+            }
+            if let Some(bounds) = key_bounds {
+                let (Some(min_key), Some(max_key)) = (segment.min_key(), segment.max_key()) else {
+                    return Some(idx);
+                };
+                if !bounds.overlaps(&min_key, &max_key) {
+                    return None;
+                }
+            }
+            if let Some((min_commit_ts, _)) = segment.commit_ts_bounds()
+                && min_commit_ts > read_ts
+            {
+                return None;
+            }
+            Some(idx)
+        })
+        .collect()
 }

src/inmem/mutable/memtable.rs

@@ -493,6 +493,41 @@ impl DynMemInner {
         }
     }
 
+    pub(crate) fn key_bounds(&self) -> (Option<KeyOwned>, Option<KeyOwned>) {
+        let min = self
+            .index
+            .iter()
+            .next()
+            .map(|entry| entry.key().key().clone());
+        let max = self
+            .index
+            .iter()
+            .next_back()
+            .map(|entry| entry.key().key().clone());
+        (min, max)
+    }
+
+    pub(crate) fn commit_ts_bounds(&self) -> Option<(Timestamp, Timestamp)> {
+        let mut iter = self.index.iter();
+        let first = iter.next()?;
+        let mut min_ts = first.key().timestamp();
+        let mut max_ts = min_ts;
+        for entry in iter {
+            let ts = entry.key().timestamp();
+            if ts < min_ts {
+                min_ts = ts;
+            }
+            if ts > max_ts {
+                max_ts = ts;
+            }
+        }
+        Some((min_ts, max_ts))
+    }
+
+    pub(crate) fn row_count(&self) -> usize {
+        self.index.len()
+    }
+
     #[cfg(all(test, feature = "tokio"))]
     pub(crate) fn inspect_versions(&self, key: &KeyOwned) -> Option<Vec<(Timestamp, bool)>> {
         let key_owned = key.clone();
@@ -689,6 +724,18 @@ impl DynMem {
         self.inner.read().has_conflict(key, snapshot_ts)
     }
 
+    pub(crate) fn key_bounds(&self) -> (Option<KeyOwned>, Option<KeyOwned>) {
+        self.inner.read().key_bounds()
+    }
+
+    pub(crate) fn commit_ts_bounds(&self) -> Option<(Timestamp, Timestamp)> {
+        self.inner.read().commit_ts_bounds()
+    }
+
+    pub(crate) fn row_count(&self) -> usize {
+        self.inner.read().row_count()
+    }
+
     /// Access the extractor.
     pub(crate) fn extractor(&self) -> &Arc<dyn KeyProjection> {
         &self.extractor

src/ondisk/sstable.rs

@@ -382,6 +382,12 @@ pub enum SsTableError {
         /// Details about why the row filter predicate was rejected.
         reason: String,
     },
+    /// Row selection length mismatch.
+    #[error("row selection length mismatch: {reason}")]
+    RowSelection {
+        /// Details about why the row selection was invalid.
+        reason: String,
+    },
     /// Invalid path component produced while building an SSTable destination.
     #[error("invalid sstable path component: {0}")]
     InvalidPath(String),
@@ -1079,15 +1085,36 @@ impl SsTableReader {
     }
 }
 
-fn row_filter_expr(predicate: &Expr, schema: &SchemaRef) -> Result<Option<Expr>, SsTableError> {
+#[derive(Debug, Clone)]
+pub(crate) struct PredicateSplit {
+    pub(crate) pushdown: Option<Expr>,
+    pub(crate) residual: Option<Expr>,
+}
+
+pub(crate) fn split_predicate_for_row_filter(
+    predicate: &Expr,
+    schema: &SchemaRef,
+) -> PredicateSplit {
     match predicate {
-        Expr::True => Ok(None),
-        Expr::False => Ok(Some(Expr::False)),
+        Expr::True => PredicateSplit {
+            pushdown: None,
+            residual: None,
+        },
+        Expr::False => PredicateSplit {
+            pushdown: Some(Expr::False),
+            residual: None,
+        },
         Expr::Cmp { column, value, .. } => {
             if scalar_matches_column(schema, column, value) {
-                Ok(Some(predicate.clone()))
+                PredicateSplit {
+                    pushdown: Some(predicate.clone()),
+                    residual: None,
+                }
             } else {
-                Ok(None)
+                PredicateSplit {
+                    pushdown: None,
+                    residual: Some(predicate.clone()),
+                }
             }
         }
         Expr::Between {
@@ -1096,79 +1123,156 @@ fn row_filter_expr(predicate: &Expr, schema: &SchemaRef) -> Result<Option<Expr>,
             if scalar_matches_column(schema, column, low)
                 && scalar_matches_column(schema, column, high)
             {
-                Ok(Some(predicate.clone()))
+                PredicateSplit {
+                    pushdown: Some(predicate.clone()),
+                    residual: None,
+                }
             } else {
-                Ok(None)
+                PredicateSplit {
+                    pushdown: None,
+                    residual: Some(predicate.clone()),
+                }
             }
         }
         Expr::InList { column, values } => {
             if scalars_match_column(schema, column, values) {
-                Ok(Some(predicate.clone()))
+                PredicateSplit {
+                    pushdown: Some(predicate.clone()),
+                    residual: None,
+                }
             } else {
-                Ok(None)
+                PredicateSplit {
+                    pushdown: None,
+                    residual: Some(predicate.clone()),
+                }
             }
         }
         Expr::StartsWith { column, .. } => {
             if is_string_column(schema, column) {
-                Ok(Some(predicate.clone()))
+                PredicateSplit {
+                    pushdown: Some(predicate.clone()),
+                    residual: None,
+                }
             } else {
-                Ok(None)
+                PredicateSplit {
+                    pushdown: None,
+                    residual: Some(predicate.clone()),
+                }
             }
         }
         Expr::IsNull { column, .. } => {
             if column_type(schema, column).is_some() {
-                Ok(Some(predicate.clone()))
+                PredicateSplit {
+                    pushdown: Some(predicate.clone()),
+                    residual: None,
+                }
             } else {
-                Ok(None)
+                PredicateSplit {
+                    pushdown: None,
+                    residual: Some(predicate.clone()),
+                }
             }
         }
-        Expr::BloomFilterEq { column, .. } => Err(SsTableError::RowFilterPredicate {
-            reason: format!(
-                "BloomFilterEq predicate on column '{column}' is not supported for row filtering"
-            ),
-        }),
-        Expr::BloomFilterInList { column, .. } => Err(SsTableError::RowFilterPredicate {
-            reason: format!(
-                "BloomFilterInList predicate on column '{column}' is not supported for row \
-                 filtering"
-            ),
-        }),
+        Expr::BloomFilterEq { .. } | Expr::BloomFilterInList { .. } => PredicateSplit {
+            pushdown: None,
+            residual: Some(predicate.clone()),
+        },
         Expr::And(children) => {
-            let mut supported = Vec::new();
+            let mut pushdown = Vec::new();
+            let mut residual = Vec::new();
             for child in children {
-                if let Some(expr) = row_filter_expr(child, schema)? {
-                    supported.push(expr);
+                let split = split_predicate_for_row_filter(child, schema);
+                if let Some(expr) = split.pushdown {
+                    pushdown.push(expr);
+                }
+                if let Some(expr) = split.residual {
+                    residual.push(expr);
                 }
             }
-            Ok(match supported.len() {
-                0 => None,
-                1 => Some(supported.remove(0)),
-                _ => Some(Expr::And(supported)),
-            })
+            PredicateSplit {
+                pushdown: combine_and(pushdown),
+                residual: combine_and(residual),
+            }
         }
         Expr::Or(children) => {
-            let mut supported = Vec::new();
+            if children.is_empty() {
+                return PredicateSplit {
+                    pushdown: Some(Expr::False),
+                    residual: None,
+                };
+            }
+            let mut pushdown = Vec::new();
             for child in children {
-                match row_filter_expr(child, schema)? {
-                    Some(expr) => supported.push(expr),
-                    None => return Ok(None),
+                let split = split_predicate_for_row_filter(child, schema);
+                if split.residual.is_some() {
+                    return PredicateSplit {
+                        pushdown: None,
+                        residual: Some(predicate.clone()),
+                    };
+                }
+                match split.pushdown {
+                    Some(expr) => pushdown.push(expr),
+                    None => {
+                        // Child is fully supported but represents no filter (True).
+                        return PredicateSplit {
+                            pushdown: None,
+                            residual: None,
+                        };
+                    }
                 }
             }
-            Ok(match supported.len() {
-                0 => None,
-                1 => Some(supported.remove(0)),
-                _ => Some(Expr::Or(supported)),
-            })
+            PredicateSplit {
+                pushdown: combine_or(pushdown),
+                residual: None,
+            }
         }
         Expr::Not(child) => {
-            Ok(row_filter_expr(child, schema)?.map(|expr| Expr::Not(Box::new(expr))))
+            let split = split_predicate_for_row_filter(child, schema);
+            if split.residual.is_some() {
+                return PredicateSplit {
+                    pushdown: None,
+                    residual: Some(predicate.clone()),
+                };
+            }
+            if split.pushdown.is_none() {
+                return PredicateSplit {
+                    pushdown: Some(Expr::False),
+                    residual: None,
+                };
+            }
+            let pushdown = split.pushdown.map(|expr| Expr::Not(Box::new(expr)));
+            PredicateSplit {
+                pushdown,
+                residual: None,
+            }
         }
-        other => Err(SsTableError::RowFilterPredicate {
-            reason: format!("unsupported predicate variant: {other:?}"),
-        }),
+        _ => PredicateSplit {
+            pushdown: None,
+            residual: Some(predicate.clone()),
+        },
+    }
+}
+
+fn combine_and(mut parts: Vec<Expr>) -> Option<Expr> {
+    match parts.len() {
+        0 => None,
+        1 => Some(parts.remove(0)),
+        _ => Some(Expr::And(parts)),
     }
 }
 
+fn combine_or(mut parts: Vec<Expr>) -> Option<Expr> {
+    match parts.len() {
+        0 => None,
+        1 => Some(parts.remove(0)),
+        _ => Some(Expr::Or(parts)),
+    }
+}
+
+fn row_filter_expr(predicate: &Expr, schema: &SchemaRef) -> Result<Option<Expr>, SsTableError> {
+    Ok(split_predicate_for_row_filter(predicate, schema).pushdown)
+}
+
 async fn build_projection_mask_for_names<E>(
     fs: Arc<dyn DynFs>,
     path: &Path,