forbid savepoints in legacy http

sqld/src/http/user/mod.rs

@@ -97,6 +97,12 @@ fn parse_queries(queries: Vec<QueryObject>) -> crate::Result<Vec<Query>> {
         out.push(query);
     }
 
+    // It's too complicated to predict the state of a transaction with savepoints in legacy http,
+    // forbid them instead.
+    if out.iter().any(|q| q.stmt.kind.is_release() || q.stmt.kind.is_release()) {
+        anyhow::bail!("savepoints are not supported in HTTP API, use hrana protocol instead");
+    }
+
     match predict_final_state(State::Init, out.iter().map(|q| &q.stmt)) {
         State::Txn => {
             return Err(Error::QueryError(

sqld/src/query_analysis.rs

@@ -171,6 +171,22 @@ impl StmtKind {
             },
         }
     }
+
+    /// Returns `true` if the stmt kind is [`Savepoint`].
+    ///
+    /// [`Savepoint`]: StmtKind::Savepoint
+    #[must_use]
+    pub fn is_savepoint(&self) -> bool {
+        matches!(self, Self::Savepoint)
+    }
+
+    /// Returns `true` if the stmt kind is [`Release`].
+    ///
+    /// [`Release`]: StmtKind::Release
+    #[must_use]
+    pub fn is_release(&self) -> bool {
+        matches!(self, Self::Release)
+    }
 }
 
 /// The state of a transaction for a series of statement
@@ -191,7 +207,8 @@ impl State {
             (State::Txn, StmtKind::TxnEnd) => State::Init,
             (state, StmtKind::Other | StmtKind::Write | StmtKind::Read) => state,
             (State::Invalid, _) => State::Invalid,
-            (State::Init, StmtKind::TxnBegin | ) => State::Txn,
+            (State::Init, StmtKind::TxnBegin) => State::Txn,
+            _ => State::Invalid,
         };
     }
 
@@ -280,7 +297,7 @@ impl Statement {
     pub fn is_read_only(&self) -> bool {
         matches!(
             self.kind,
-            StmtKind::Read | StmtKind::TxnEnd | StmtKind::TxnBegin
+            StmtKind::Read | StmtKind::TxnEnd | StmtKind::TxnBegin | StmtKind::Release | StmtKind::Savepoint
         )
     }
 }