fix drop tables

Author: Shubham8287

crates/datastore/src/locking_tx_datastore/committed_state.rs

@@ -44,6 +44,7 @@ use spacetimedb_table::{
 };
 use std::collections::BTreeMap;
 use std::sync::Arc;
+use thin_vec::ThinVec;
 
 /// Contains the live, in-memory snapshot of a database. This structure
 /// is exposed in order to support tools wanting to process the commit
@@ -593,12 +594,23 @@ impl CommittedState {
     pub(super) fn merge(&mut self, tx_state: TxState, ctx: &ExecutionContext) -> TxData {
         let mut tx_data = TxData::default();
 
+        // This transaction may have dropped tables.
+        // After applying `merge_apply_deletes` and `merge_apply_inserts`,
+        // any tables no longer referenced by `st_table` should be
+        // removed from the committed state.
+        let mut tables_to_drop = thin_vec::ThinVec::<TableId>::new();
+
         // First, apply deletes. This will free up space in the committed tables.
-        self.merge_apply_deletes(&mut tx_data, tx_state.delete_tables);
+        self.merge_apply_deletes(&mut tx_data, &mut tables_to_drop, tx_state.delete_tables);
 
         // Then, apply inserts. This will re-fill the holes freed by deletions
         // before allocating new pages.
-        self.merge_apply_inserts(&mut tx_data, tx_state.insert_tables, tx_state.blob_store);
+        self.merge_apply_inserts(
+            &mut tx_data,
+            &mut tables_to_drop,
+            tx_state.insert_tables,
+            tx_state.blob_store,
+        );
 
         // If the TX will be logged, record its projected tx offset,
         // then increment the counter.
@@ -607,10 +619,19 @@ impl CommittedState {
             self.next_tx_offset += 1;
         }
 
+        for table_id in tables_to_drop {
+            self.tables.remove(&table_id);
+        }
+
         tx_data
     }
 
-    fn merge_apply_deletes(&mut self, tx_data: &mut TxData, delete_tables: BTreeMap<TableId, DeleteTable>) {
+    fn merge_apply_deletes(
+        &mut self,
+        tx_data: &mut TxData,
+        dropped_table_ids: &mut ThinVec<TableId>,
+        delete_tables: BTreeMap<TableId, DeleteTable>,
+    ) {
         for (table_id, row_ptrs) in delete_tables {
             if let (Some(table), blob_store, _) = self.get_table_and_blob_store_mut(table_id) {
                 let mut deletes = Vec::with_capacity(row_ptrs.len());
@@ -626,6 +647,14 @@ impl CommittedState {
                     let pv = table
                         .delete(blob_store, row_ptr, |row| row.to_product_value())
                         .expect("Delete for non-existent row!");
+
+                    if table_id == ST_TABLE_ID {
+                        let st_table_row =
+                            StTableRow::deserialize(ValueDeserializer::from_ref(&AlgebraicValue::Product(pv.clone())))
+                                .expect("st_table row should deserialize");
+                        dropped_table_ids.push(st_table_row.table_id);
+                    }
+
                     deletes.push(pv);
                 }
 
@@ -642,6 +671,7 @@ impl CommittedState {
     fn merge_apply_inserts(
         &mut self,
         tx_data: &mut TxData,
+        dropped_table_ids: &mut ThinVec<TableId>,
         insert_tables: BTreeMap<TableId, Table>,
         tx_blob_store: impl BlobStore,
     ) {
@@ -665,6 +695,15 @@ impl CommittedState {
                     .insert(page_pool, commit_blob_store, &pv)
                     .expect("Failed to insert when merging commit");
 
+                // If we inserted a row back into `st_table`,
+                // it means transaction only updates a row and do not drop the table.
+                if table_id == ST_TABLE_ID {
+                    let st_table_row =
+                        StTableRow::deserialize(ValueDeserializer::from_ref(&AlgebraicValue::Product(pv.clone())))
+                            .expect("st_table row should deserialize");
+                    dropped_table_ids.retain(|&id| id != st_table_row.table_id);
+                }
+
                 inserts.push(pv);
             }
 
@@ -717,13 +756,6 @@ impl CommittedState {
                 table.with_mut_schema(|s| s.remove_index(index_id));
                 self.index_id_map.remove(&index_id);
             }
-            // A table was removed. Add it back.
-            TableRemoved(table_id, table) => {
-                // We don't need to deal with sub-components.
-                // That is, we don't need to add back indices and such.
-                // Instead, there will be separate pending schema changes like `IndexRemoved`.
-                self.tables.insert(table_id, table);
-            }
             // A table was added. Remove it.
             TableAdded(table_id) => {
                 // We don't need to deal with sub-components.

crates/datastore/src/locking_tx_datastore/datastore.rs

@@ -675,6 +675,7 @@ pub struct TxMetrics {
     exec_metrics: ExecutionMetrics,
 }
 
+#[derive(Default)]
 struct TableStats {
     /// The number of rows in the table after this transaction.
     ///
@@ -715,16 +716,16 @@ impl TxMetrics {
                 let mut table_stats =
                     <HashMap<_, _, _> as HashCollectionExt>::with_capacity(tx_data.num_tables_affected());
                 for (table_id, _) in tx_data.table_ids_and_names() {
-                    let table = committed_state
-                        .get_table(table_id)
-                        .expect("should have a table in committed state for one in tx data");
                     table_stats.insert(
                         table_id,
-                        TableStats {
-                            row_count: table.row_count,
-                            bytes_occupied_overestimate: table.bytes_occupied_overestimate(),
-                            num_indices: table.num_indices(),
-                        },
+                        committed_state
+                            .get_table(table_id)
+                            .map(|table| TableStats {
+                                row_count: table.row_count,
+                                bytes_occupied_overestimate: table.bytes_occupied_overestimate(),
+                                num_indices: table.num_indices(),
+                            })
+                            .unwrap_or_default(),
                     );
                 }
                 table_stats
@@ -3082,9 +3083,7 @@ mod tests {
                 PendingSchemaChange::SequenceRemoved(..),
                 PendingSchemaChange::ConstraintRemoved(..),
                 PendingSchemaChange::ConstraintRemoved(..),
-                PendingSchemaChange::TableRemoved(removed_table_id, _)
             ]
-                if *removed_table_id == table_id
         );
         let _ = datastore.rollback_mut_tx(tx);
 
@@ -3096,7 +3095,17 @@ mod tests {
             "Table should still exist",
         );
         assert_eq!(all_rows(&datastore, &tx, table_id), [row]);
+        let _ = datastore.rollback_mut_tx(tx);
+
+        let mut tx = begin_mut_tx(&datastore);
+        assert!(datastore.drop_table_mut_tx(&mut tx, table_id).is_ok());
+        commit(&datastore, tx)?;
 
+        let tx = begin_mut_tx(&datastore);
+        assert!(
+            !datastore.table_id_exists_mut_tx(&tx, &table_id),
+            "Table should be removed",
+        );
         Ok(())
     }
 

crates/datastore/src/locking_tx_datastore/mut_tx.rs

@@ -352,15 +352,14 @@ impl MutTxId {
             )?;
         }
 
+        // Delete all rows in the table.
+        let ptrs: Vec<_> = self.iter(table_id)?.map(|row| row.pointer()).collect();
+        for ptr in ptrs {
+            self.delete(table_id, ptr)?;
+        }
+
         // Delete the table and its rows and indexes from memory.
         self.tx_state.insert_tables.remove(&table_id);
-        self.tx_state.delete_tables.remove(&table_id);
-        let commit_table = self
-            .committed_state_write_lock
-            .tables
-            .remove(&table_id)
-            .expect("there should be a schema in the committed state if we reach here");
-        self.push_schema_change(PendingSchemaChange::TableRemoved(table_id, commit_table));
 
         Ok(())
     }

crates/datastore/src/locking_tx_datastore/tx_state.rs

@@ -95,8 +95,6 @@ pub enum PendingSchemaChange {
     /// If adding this index caused the pointer map to be removed,
     /// it will be present here.
     IndexAdded(TableId, IndexId, Option<PointerMap>),
-    /// The [`Table`] with [`TableId`] was removed.
-    TableRemoved(TableId, Table),
     /// The table with [`TableId`] was added.
     TableAdded(TableId),
     /// The access of the table with [`TableId`] was changed.