Properly disable MultiCFIterator in WritePrepared/UnPreparedTxnDBs (#12883)

Summary:
MultiCfIterators (`CoalescingIterator` and `AttributeGroupIterator`) are not yet compatible with write-prepared/write-unprepared transactions, yet (write-committed is fine). This fix includes the following.

- Properly return `ErrorIterator` if the user attempts to use the `CoalescingIterator` or `AttributeGroupIterator` in WritePreparedTxnDB (and WriteUnpreparedTxnDB)
- Set `use_multi_cf_iterator = 0` if `use_txn=1` and `txn_write_policy != 0 (WRITE_COMMITTED)` in stress test.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/12883

Test Plan:
Works
```
./db_stress ... --use_txn=1 --txn_write_policy=0 --use_multi_cf_iterator=1
```

Fails
```
./db_stress ... --use_txn=1 --txn_write_policy=1 --use_multi_cf_iterator=1
```

Reviewed By: cbi42

Differential Revision: D60190784

Pulled By: jaykorean

fbshipit-source-id: 3bc1093e81a4ef5753ba9b32c5aea997c21bfd33

tools/db_crashtest.py

@@ -844,6 +844,8 @@ def finalize_and_sanitize(src_params):
         # Wide-column pessimistic transaction APIs are initially supported for
         # WriteCommitted only
         dest_params["use_put_entity_one_in"] = 0
+        # MultiCfIterator is currently only compatible with write committed policy
+        dest_params["use_multi_cf_iterator"] = 0        
     # TODO(hx235): enable test_multi_ops_txns with fault injection after stabilizing the CI
     if dest_params.get("test_multi_ops_txns") == 1:
         dest_params["write_fault_one_in"] = 0

utilities/transactions/write_prepared_txn_db.h

@@ -13,6 +13,7 @@
 #include <unordered_map>
 #include <vector>
 
+#include "db/attribute_group_iterator_impl.h"
 #include "db/db_iter.h"
 #include "db/pre_release_callback.h"
 #include "db/read_callback.h"
@@ -101,6 +102,22 @@ class WritePreparedTxnDB : public PessimisticTransactionDB {
                       const std::vector<ColumnFamilyHandle*>& column_families,
                       std::vector<Iterator*>* iterators) override;
 
+  using DB::NewCoalescingIterator;
+  std::unique_ptr<Iterator> NewCoalescingIterator(
+      const ReadOptions& /*options*/,
+      const std::vector<ColumnFamilyHandle*>& /*column_families*/) override {
+    return std::unique_ptr<Iterator>(
+        NewErrorIterator(Status::NotSupported("Not supported yet")));
+  }
+
+  using DB::NewAttributeGroupIterator;
+  std::unique_ptr<AttributeGroupIterator> NewAttributeGroupIterator(
+      const ReadOptions& /*options*/,
+      const std::vector<ColumnFamilyHandle*>& /*column_families*/) override {
+    return NewAttributeGroupErrorIterator(
+        Status::NotSupported("Not supported yet"));
+  }
+
   // Check whether the transaction that wrote the value with sequence number seq
   // is visible to the snapshot with sequence number snapshot_seq.
   // Returns true if commit_seq <= snapshot_seq