fix(postgres): lock TransactWriteItems items in key order, cancel on deadlock

.github/workflows/integration.yml

@@ -297,12 +297,14 @@ jobs:
 
       # The control plane for vector indexes is not reachable over the wire while
       # this backend declares no vector search capability, so its tests drive the
-      # storage layer directly against this job's PostgreSQL. They build their own
-      # throwaway databases; the connection string is the server, not a database.
+      # storage layer directly against this job's PostgreSQL. The write-transaction
+      # conflict tests force a deadlock, which also needs direct access. They build
+      # their own throwaway databases; the connection string is the server, not a
+      # database.
       - name: Run PostgreSQL storage-level tests
         env:
           EXTENDDB_TEST_PG_CONNECTION_STRING: postgresql://postgres:devpass@127.0.0.1:5432
-        run: cargo test --release -p extenddb-storage-postgres --test vector_control_plane
+        run: cargo test --release -p extenddb-storage-postgres --test vector_control_plane --test twi_conflict
 
       # The daemonized server logs to syslog; dump it so server-side failures
       # are diagnosable from the job log.

crates/core/src/types/transaction.rs

@@ -296,6 +296,16 @@ impl CancellationReason {
         }
     }
 
+    /// Create a reason for an item that another transaction holds.
+    #[must_use]
+    pub fn transaction_conflict() -> Self {
+        Self {
+            code: "TransactionConflict".to_owned(),
+            message: Some("Transaction is ongoing for the item".to_owned()),
+            item: None,
+        }
+    }
+
     /// Create a reason for a validation error.
     #[must_use]
     pub fn validation_error(msg: impl Into<String>) -> Self {

crates/storage-postgres/src/data/mod.rs

@@ -92,7 +92,7 @@ macro_rules! bind_sk_fetch_optional {
                     .await
             }
         }
-        .map_err(|e| extenddb_storage::error::StorageError::Internal(e.to_string()))
+        .map_err($crate::data::index::db_error)
     };
 }
 
@@ -124,7 +124,7 @@ macro_rules! bind_sk_execute {
                     .await
             }
         }
-        .map_err(|e| extenddb_storage::error::StorageError::Internal(e.to_string()))
+        .map_err($crate::data::index::db_error)
     };
 }