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prathmeshccprathmeshcc
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feat(spanner): define IsolationLevel enum for Spanner transactions (#15853)
* feat(spanner): add support for snapshot isolation
1 parent 113d8fa commit 3959c49

4 files changed

Lines changed: 133 additions & 4 deletions

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‎google/cloud/spanner/options.h‎

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@@ -46,6 +46,7 @@
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#include "google/cloud/spanner/polling_policy.h"
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#include "google/cloud/spanner/request_priority.h"
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#include "google/cloud/spanner/retry_policy.h"
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#include "google/cloud/spanner/transaction.h"
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#include "google/cloud/spanner/version.h"
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#include "google/cloud/options.h"
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#include "absl/types/variant.h"
@@ -415,6 +416,15 @@ struct ExcludeTransactionFromChangeStreamsOption {
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using Type = bool;
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};
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/**
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* Option for `google::cloud::Options` to set the transaction isolation level.
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*
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* @ingroup google-cloud-spanner-options
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*/
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struct TransactionIsolationLevelOption {
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using Type = spanner::Transaction::IsolationLevel;
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};
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/**
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* Option for `google::cloud::Options` to return additional statistics
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* about the committed transaction in a `spanner::CommitResult`.

‎google/cloud/spanner/transaction.cc‎

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@@ -54,6 +54,22 @@ ProtoReadLockMode(
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}
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}
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google::spanner::v1::TransactionOptions_IsolationLevel ProtoIsolationLevel(
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absl::optional<Transaction::IsolationLevel> const& isolation_level) {
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if (!isolation_level) {
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return google::spanner::v1::TransactionOptions::ISOLATION_LEVEL_UNSPECIFIED;
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}
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switch (*isolation_level) {
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case Transaction::IsolationLevel::kSerializable:
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return google::spanner::v1::TransactionOptions::SERIALIZABLE;
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case Transaction::IsolationLevel::kRepeatableRead:
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return google::spanner::v1::TransactionOptions::REPEATABLE_READ;
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default:
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return google::spanner::v1::TransactionOptions::
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ISOLATION_LEVEL_UNSPECIFIED;
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}
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}
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5773
google::spanner::v1::TransactionOptions MakeOpts(
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google::spanner::v1::TransactionOptions_ReadOnly ro_opts) {
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google::spanner::v1::TransactionOptions opts;
@@ -62,13 +78,21 @@ google::spanner::v1::TransactionOptions MakeOpts(
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}
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google::spanner::v1::TransactionOptions MakeOpts(
65-
google::spanner::v1::TransactionOptions_ReadWrite rw_opts) {
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google::spanner::v1::TransactionOptions_ReadWrite rw_opts,
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absl::optional<Transaction::IsolationLevel> isolation_level) {
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google::spanner::v1::TransactionOptions opts;
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*opts.mutable_read_write() = std::move(rw_opts);
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auto const& current = internal::CurrentOptions();
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if (current.get<ExcludeTransactionFromChangeStreamsOption>()) {
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opts.set_exclude_txn_from_change_streams(true);
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}
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if (isolation_level) {
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opts.set_isolation_level(ProtoIsolationLevel(isolation_level));
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} else if (current.has<TransactionIsolationLevelOption>()) {
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opts.set_isolation_level(
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ProtoIsolationLevel(current.get<TransactionIsolationLevelOption>()));
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}
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7296
return opts;
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}
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@@ -103,6 +127,13 @@ Transaction::ReadWriteOptions& Transaction::ReadWriteOptions::WithTag(
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return *this;
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}
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Transaction::ReadWriteOptions&
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Transaction::ReadWriteOptions::WithIsolationLevel(
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IsolationLevel isolation_level) {
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isolation_level_ = isolation_level;
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return *this;
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}
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Transaction::SingleUseOptions::SingleUseOptions(ReadOnlyOptions opts) {
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ro_opts_ = std::move(opts.ro_opts_);
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}
@@ -129,7 +160,8 @@ Transaction::Transaction(ReadOnlyOptions opts) {
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Transaction::Transaction(ReadWriteOptions opts) {
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google::spanner::v1::TransactionSelector selector;
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*selector.mutable_begin() = MakeOpts(std::move(opts.rw_opts_));
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*selector.mutable_begin() =
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MakeOpts(std::move(opts.rw_opts_), opts.isolation_level_);
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auto const route_to_leader = true; // read-write
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impl_ = std::make_shared<spanner_internal::TransactionImpl>(
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std::move(selector), route_to_leader,
@@ -138,7 +170,8 @@ Transaction::Transaction(ReadWriteOptions opts) {
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Transaction::Transaction(Transaction const& txn, ReadWriteOptions opts) {
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google::spanner::v1::TransactionSelector selector;
141-
*selector.mutable_begin() = MakeOpts(std::move(opts.rw_opts_));
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*selector.mutable_begin() =
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MakeOpts(std::move(opts.rw_opts_), opts.isolation_level_);
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auto const route_to_leader = true; // read-write
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impl_ = std::make_shared<spanner_internal::TransactionImpl>(
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*txn.impl_, std::move(selector), route_to_leader,
@@ -155,7 +188,8 @@ Transaction::Transaction(SingleUseOptions opts) {
155188

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Transaction::Transaction(ReadWriteOptions opts, SingleUseCommitTag) {
157190
google::spanner::v1::TransactionSelector selector;
158-
*selector.mutable_single_use() = MakeOpts(std::move(opts.rw_opts_));
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*selector.mutable_single_use() =
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MakeOpts(std::move(opts.rw_opts_), opts.isolation_level_);
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auto const route_to_leader = true; // write
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impl_ = std::make_shared<spanner_internal::TransactionImpl>(
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std::move(selector), route_to_leader,

‎google/cloud/spanner/transaction.h‎

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@@ -57,6 +57,37 @@ GOOGLE_CLOUD_CPP_INLINE_NAMESPACE_BEGIN
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*/
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class Transaction {
5959
public:
60+
/**
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* Defines the isolation level for a transaction.
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*
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* This determines how concurrent transactions interact with each other and
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* what consistency guarantees are provided for read and write operations.
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*
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* @note This setting only applies to read-write transactions.
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*
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* See the `v1::TransactionOptions` proto for more details.
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*
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* @see https://docs.cloud.google.com/spanner/docs/isolation-levels
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*/
72+
enum class IsolationLevel {
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/// The isolation level is not specified, using the backend default.
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kUnspecified,
75+
/**
76+
* All transactions appear as if they executed in a serial order.
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* This is the default isolation level for read-write transactions.
78+
*/
79+
kSerializable,
80+
/**
81+
* All reads performed during the transaction observe a consistent snapshot
82+
* of the database. The transaction is only successfully committed in the
83+
* absence of conflicts between its updates and any concurrent updates
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* that have occurred since that snapshot. Consequently, in contrast to
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* `kSerializable` transactions, only write-write conflicts are detected in
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* snapshot transactions.
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*/
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kRepeatableRead,
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};
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6091
/**
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* Options for ReadOnly transactions.
6293
*/
@@ -103,10 +134,17 @@ class Transaction {
103134
// A tag used for collecting statistics about the transaction.
104135
ReadWriteOptions& WithTag(absl::optional<std::string> tag);
105136

137+
// Sets the isolation level for the transaction. This controls how the
138+
// transaction interacts with other concurrent transactions, primarily
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// regarding data consistency for reads and writes.
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// See `IsolationLevel` enum for possible values.
141+
ReadWriteOptions& WithIsolationLevel(IsolationLevel isolation_level);
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private:
107144
friend Transaction;
108145
google::spanner::v1::TransactionOptions_ReadWrite rw_opts_;
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absl::optional<std::string> tag_;
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absl::optional<IsolationLevel> isolation_level_;
110148
};
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/**

‎google/cloud/spanner/transaction_test.cc‎

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@@ -14,6 +14,8 @@
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#include "google/cloud/spanner/transaction.h"
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#include "google/cloud/spanner/internal/session.h"
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#include "google/cloud/spanner/options.h"
18+
#include "google/cloud/options.h"
1719
#include <gmock/gmock.h>
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1921
namespace google {
@@ -169,6 +171,51 @@ TEST(Transaction, MultiplexedPreviousTransactionId) {
169171
});
170172
}
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174+
TEST(Transaction, IsolationLevelPrecedence) {
175+
internal::OptionsSpan span(Options{}.set<TransactionIsolationLevelOption>(
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Transaction::IsolationLevel::kSerializable));
177+
178+
// Case 1: Per-call overrides default options
179+
auto opts = Transaction::ReadWriteOptions().WithIsolationLevel(
180+
Transaction::IsolationLevel::kRepeatableRead);
181+
Transaction txn = MakeReadWriteTransaction(opts);
182+
spanner_internal::Visit(
183+
txn, [](spanner_internal::SessionHolder&,
184+
StatusOr<google::spanner::v1::TransactionSelector>& s,
185+
spanner_internal::TransactionContext const&) {
186+
EXPECT_EQ(s->begin().isolation_level(),
187+
google::spanner::v1::TransactionOptions::REPEATABLE_READ);
188+
return 0;
189+
});
190+
191+
// Case 2: Fallback to client default
192+
auto opts_default = Transaction::ReadWriteOptions();
193+
Transaction txn_default = MakeReadWriteTransaction(opts_default);
194+
spanner_internal::Visit(
195+
txn_default, [](spanner_internal::SessionHolder&,
196+
StatusOr<google::spanner::v1::TransactionSelector>& s,
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spanner_internal::TransactionContext const&) {
198+
EXPECT_EQ(s->begin().isolation_level(),
199+
google::spanner::v1::TransactionOptions::SERIALIZABLE);
200+
return 0;
201+
});
202+
}
203+
204+
TEST(Transaction, IsolationLevelNotSpecified) {
205+
// Case: Isolation not specified in transaction level or client level
206+
auto opts = Transaction::ReadWriteOptions();
207+
Transaction txn = MakeReadWriteTransaction(opts);
208+
spanner_internal::Visit(
209+
txn, [](spanner_internal::SessionHolder&,
210+
StatusOr<google::spanner::v1::TransactionSelector>& s,
211+
spanner_internal::TransactionContext const&) {
212+
EXPECT_EQ(s->begin().isolation_level(),
213+
google::spanner::v1::TransactionOptions::
214+
ISOLATION_LEVEL_UNSPECIFIED);
215+
return 0;
216+
});
217+
}
218+
172219
TEST(Transaction, ReadWriteOptionsWithTag) {
173220
auto opts = Transaction::ReadWriteOptions().WithTag("test-tag");
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Transaction txn = MakeReadWriteTransaction(opts);

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