feat(spanner): define IsolationLevel enum for Spanner transactions #15853
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Summary of ChangesHello @prathmeshcc, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request enhances the Google Cloud Spanner C++ client library by introducing explicit support for transaction isolation levels. It defines a new Highlights
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Code Review
This pull request introduces an IsolationLevel enum and the corresponding TransactionIsolationLevelOption to allow users to configure the isolation level for read-write transactions. The changes are well-structured and follow existing patterns in the codebase. The new functionality is well-tested with new unit and integration tests that verify the option handling and precedence. The implementation appears correct and complete. I have one minor suggestion to remove some debugging output from the unit tests.
| TEST(Transaction, IsolationLevel) { | ||
| auto opts = Transaction::ReadWriteOptions().WithIsolationLevel( | ||
| IsolationLevel::kRepeatableRead); | ||
| Transaction txn = MakeReadWriteTransaction(opts); | ||
| spanner_internal::Visit( | ||
| txn, [](spanner_internal::SessionHolder&, | ||
| StatusOr<google::spanner::v1::TransactionSelector>& s, | ||
| spanner_internal::TransactionContext const&) { | ||
| EXPECT_TRUE(s->has_begin()); | ||
| EXPECT_TRUE(s->begin().has_read_write()); | ||
| EXPECT_EQ(s->begin().isolation_level(), | ||
| google::spanner::v1::TransactionOptions::REPEATABLE_READ); | ||
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| std::cout << "Isolation Level: " | ||
| << s->begin().isolation_level() << std::endl; | ||
| return 0; | ||
| }); | ||
| } | ||
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| TEST(Transaction, IsolationLevelPrecedence) { | ||
| internal::OptionsSpan span(Options{}.set<TransactionIsolationLevelOption>( | ||
| IsolationLevel::kSerializable)); | ||
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| // Case 1: Per-call overrides client default | ||
| auto opts = Transaction::ReadWriteOptions().WithIsolationLevel( | ||
| IsolationLevel::kRepeatableRead); | ||
| Transaction txn = MakeReadWriteTransaction(opts); | ||
| spanner_internal::Visit( | ||
| txn, [](spanner_internal::SessionHolder&, | ||
| StatusOr<google::spanner::v1::TransactionSelector>& s, | ||
| spanner_internal::TransactionContext const&) { | ||
| EXPECT_EQ(s->begin().isolation_level(), | ||
| google::spanner::v1::TransactionOptions::REPEATABLE_READ); | ||
| std::cout << "Isolation Level: " | ||
| << s->begin().isolation_level() << std::endl; | ||
| return 0; | ||
| }); | ||
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| // Case 2: Fallback to client default | ||
| auto opts_default = Transaction::ReadWriteOptions(); | ||
| Transaction txn_default = MakeReadWriteTransaction(opts_default); | ||
| spanner_internal::Visit( | ||
| txn_default, [](spanner_internal::SessionHolder&, | ||
| StatusOr<google::spanner::v1::TransactionSelector>& s, | ||
| spanner_internal::TransactionContext const&) { | ||
| EXPECT_EQ(s->begin().isolation_level(), | ||
| google::spanner::v1::TransactionOptions::SERIALIZABLE); | ||
| std::cout << "Isolation Level: " | ||
| << s->begin().isolation_level() << std::endl; | ||
| return 0; | ||
| }); | ||
| } |
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The new tests TEST(Transaction, IsolationLevel) and TEST(Transaction, IsolationLevelPrecedence) contain std::cout statements (lines 187-188, 207-208, and 221-222) that seem to be for debugging. Please remove them to keep the test output clean.
Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## main #15853 +/- ##
==========================================
- Coverage 92.95% 92.94% -0.01%
==========================================
Files 2458 2458
Lines 227589 227661 +72
==========================================
+ Hits 211553 211605 +52
- Misses 16036 16056 +20 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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| opts.set_isolation_level( | ||
| static_cast<google::spanner::v1::TransactionOptions::IsolationLevel>( | ||
| isolation_level)); |
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We strive to not tie the C++ enum values to the protobuf enum values. See, for example, LockHint, OrderBy, ReadLockMode, ReplicaType, RequestPriority, etc. Please continue that by introducing an explicit mapping here (removing the static_cast and specific enum class values).
| for (auto const& row : rows) { | ||
| if (!row) return row.status(); | ||
| } | ||
| // std::cout << "Transaction is active." << std::endl; |
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Acknowledged. Will remove this in the next push.
| // std::cout << "Transaction is active." << std::endl; | ||
| return Mutations{}; | ||
| }, | ||
| Options{}.set<TransactionIsolationLevelOption>( |
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Would this test behave any differently if this was ignored? That is, what are we testing?
| } | ||
| return Mutations{}; | ||
| }, | ||
| Options{}.set<TransactionIsolationLevelOption>( |
| *selector.mutable_begin() = | ||
| MakeOpts(std::move(opts.rw_opts_), opts.isolation_level_); |
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[GitHub seems to have dropped a comment here. Apologies if you see this twice.]
It seems weird that the isolation level appears to only be useful in read-write mode yet it wasn't made part of message ReadWrite. Is that appearance true (and the protos should probably be fixed, in which case we would not need any special treatment here), or are we being too specific in making the isolation mode a member of ReadWriteOptions?
2 participants
This PR introduces the IsolationLevel enum class in google/cloud/spanner/isolation_level.h.
This enum maps to the google.spanner.v1.TransactionOptions.IsolationLevel protobuf and defines the supported isolation levels for Cloud Spanner read-write transactions:
This addition is a prerequisite for allowing users to configure the isolation level (specifically Repeatable Read) in transaction options.