UniStore: Use epoch with microsecond resolution as RV (#92638)

* Use epoch with microsecond resolution as RV

* fix backend tests

* Add solution for when the clock goes back

* Add solution for when the clock goes back

* generate mocks

* go lint

* remove comment

* Use Greatest instead of max in msyql and postgres

* update tests

* Update pkg/storage/unified/sql/sqltemplate/dialect_sqlite.go

Co-authored-by: Diego Augusto Molina <diegoaugustomolina@gmail.com>

* cast to bigint

* add additional round trip

* increment the RV using 2 sql round trips instead of 3

* cleanup comments

* cast unix timestamp to integer

* fix postgres query

* remove old increment test data

* remove greatest

* cast unix_timestamp to signed

* Use statement_timestamp instead of clock_timestamp

---------

Co-authored-by: Diego Augusto Molina <diegoaugustomolina@gmail.com>

pkg/storage/unified/sql/sqltemplate/dialect.go

@@ -62,6 +62,9 @@ type Dialect interface {
 	//		WHERE id = ?
 	//		{{ .SelectFor "Update NoWait" }}; -- will be uppercased
 	SelectFor(...string) (string, error)
+
+	// CurrentEpoch returns the current epoch value for the database in microseconds.
+	CurrentEpoch() string
 }
 
 // RowLockingClause represents a row-locking clause in a SELECT statement.

pkg/storage/unified/sql/sqltemplate/dialect_mysql.go

@@ -33,3 +33,7 @@ func (backtickIdent) Ident(s string) (string, error) {
 		return s
 	})
 }
+
+func (mysql) CurrentEpoch() string {
+	return "CAST(FLOOR(UNIX_TIMESTAMP(NOW(6)) * 1000000) AS SIGNED)"
+}

pkg/storage/unified/sql/sqltemplate/dialect_postgresql.go

@@ -35,3 +35,7 @@ func (p postgresql) Ident(s string) (string, error) {
 
 	return p.standardIdent.Ident(s)
 }
+
+func (postgresql) CurrentEpoch() string {
+	return "(EXTRACT(EPOCH FROM statement_timestamp()) * 1000000)::BIGINT"
+}

pkg/storage/unified/sql/sqltemplate/dialect_sqlite.go

@@ -16,3 +16,8 @@ type sqlite struct {
 	argPlaceholderFunc
 	name
 }
+
+func (sqlite) CurrentEpoch() string {
+	// Alternative approaches like `unixepoch('subsecond') * 1000000` returns millisecond precision.
+	return "CAST((julianday('now') - 2440587.5) * 86400000000.0 AS BIGINT)"
+}

pkg/storage/unified/sql/sqltemplate/mocks/SQLTemplateIface.go

@@ -171,6 +171,51 @@ func (_c *SQLTemplate_ArgPlaceholder_Call) RunAndReturn(run func(int) string) *S
 	return _c
 }
 
+// CurrentEpoch provides a mock function with given fields:
+func (_m *SQLTemplate) CurrentEpoch() string {
+	ret := _m.Called()
+
+	if len(ret) == 0 {
+		panic("no return value specified for CurrentEpoch")
+	}
+
+	var r0 string
+	if rf, ok := ret.Get(0).(func() string); ok {
+		r0 = rf()
+	} else {
+		r0 = ret.Get(0).(string)
+	}
+
+	return r0
+}
+
+// SQLTemplate_CurrentEpoch_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'CurrentEpoch'
+type SQLTemplate_CurrentEpoch_Call struct {
+	*mock.Call
+}
+
+// CurrentEpoch is a helper method to define mock.On call
+func (_e *SQLTemplate_Expecter) CurrentEpoch() *SQLTemplate_CurrentEpoch_Call {
+	return &SQLTemplate_CurrentEpoch_Call{Call: _e.mock.On("CurrentEpoch")}
+}
+
+func (_c *SQLTemplate_CurrentEpoch_Call) Run(run func()) *SQLTemplate_CurrentEpoch_Call {
+	_c.Call.Run(func(args mock.Arguments) {
+		run()
+	})
+	return _c
+}
+
+func (_c *SQLTemplate_CurrentEpoch_Call) Return(_a0 string) *SQLTemplate_CurrentEpoch_Call {
+	_c.Call.Return(_a0)
+	return _c
+}
+
+func (_c *SQLTemplate_CurrentEpoch_Call) RunAndReturn(run func() string) *SQLTemplate_CurrentEpoch_Call {
+	_c.Call.Return(run)
+	return _c
+}
+
 // DialectName provides a mock function with given fields:
 func (_m *SQLTemplate) DialectName() string {
 	ret := _m.Called()

pkg/storage/unified/sql/sqltemplate/mocks/WithResults.go

@@ -171,6 +171,51 @@ func (_c *WithResults_ArgPlaceholder_Call[T]) RunAndReturn(run func(int) string)
 	return _c
 }
 
+// CurrentEpoch provides a mock function with given fields:
+func (_m *WithResults[T]) CurrentEpoch() string {
+	ret := _m.Called()
+
+	if len(ret) == 0 {
+		panic("no return value specified for CurrentEpoch")
+	}
+
+	var r0 string
+	if rf, ok := ret.Get(0).(func() string); ok {
+		r0 = rf()
+	} else {
+		r0 = ret.Get(0).(string)
+	}
+
+	return r0
+}
+
+// WithResults_CurrentEpoch_Call is a *mock.Call that shadows Run/Return methods with type explicit version for method 'CurrentEpoch'
+type WithResults_CurrentEpoch_Call[T interface{}] struct {
+	*mock.Call
+}
+
+// CurrentEpoch is a helper method to define mock.On call
+func (_e *WithResults_Expecter[T]) CurrentEpoch() *WithResults_CurrentEpoch_Call[T] {
+	return &WithResults_CurrentEpoch_Call[T]{Call: _e.mock.On("CurrentEpoch")}
+}
+
+func (_c *WithResults_CurrentEpoch_Call[T]) Run(run func()) *WithResults_CurrentEpoch_Call[T] {
+	_c.Call.Run(func(args mock.Arguments) {
+		run()
+	})
+	return _c
+}
+
+func (_c *WithResults_CurrentEpoch_Call[T]) Return(_a0 string) *WithResults_CurrentEpoch_Call[T] {
+	_c.Call.Return(_a0)
+	return _c
+}
+
+func (_c *WithResults_CurrentEpoch_Call[T]) RunAndReturn(run func() string) *WithResults_CurrentEpoch_Call[T] {
+	_c.Call.Return(run)
+	return _c
+}
+
 // DialectName provides a mock function with given fields:
 func (_m *WithResults[T]) DialectName() string {
 	ret := _m.Called()