db

package
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Published: Dec 4, 2024 License: Apache-2.0 Imports: 4 Imported by: 0

Documentation

Overview

Package db defines common database interface.

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

func Configured

func Configured() bool

Configured returns true if there's at least one registered implementation.

func Kinds

func Kinds() []string

Kinds returns IDs of registered database implementations.

func Register

func Register(db Impl)

Register registers a database implementation.

Must be called during init() time.

func VisitImpls

func VisitImpls(cb func(db *Impl))

VisitImpls calls the callback for all registered implementation.

Types

type DB

type DB interface {
	// Kind identifies this particular database implementation.
	//
	// Among other things it is used in Cloud Tasks messages involved in the
	// implementation of the distributed sweeping.
	Kind() string

	// Defer defers the execution of the callback until the transaction lands.
	//
	// Panics if called outside of a transaction.
	//
	// The callback will receive the original non-transactional context.
	Defer(context.Context, func(context.Context))

	// SaveReminder persists reminder in a transaction context.
	//
	// Tags retriable errors as transient.
	SaveReminder(context.Context, *reminder.Reminder) error

	// DeleteReminder deletes reminder in a non-transaction context.
	DeleteReminder(context.Context, *reminder.Reminder) error

	// FetchRemindersMeta fetches Reminders with Ids in [low..high) range.
	//
	// RawPayload of Reminders should not be fetched.
	// Both fresh & stale reminders should be fetched.
	// The reminders should be returned in order of ascending Id.
	//
	// In case of error, partial result of fetched Reminders so far should be
	// returned alongside the error. The caller will later call this method again
	// to fetch the remaining of Reminders in range of [<lastReturned.Id+1> .. high).
	FetchRemindersMeta(ctx context.Context, low, high string, limit int) ([]*reminder.Reminder, error)

	// FetchReminderRawPayloads fetches raw payloads of a batch of Reminders.
	//
	// The Reminder objects are re-used in the returned batch.
	// If any Reminder is no longer found, it is silently omitted in the returned
	// batch.
	// In case of any other error, partial result of fetched Reminders so far
	// should be returned alongside the error.
	FetchReminderRawPayloads(context.Context, []*reminder.Reminder) ([]*reminder.Reminder, error)
}

DB abstracts out specific storage implementation.

func NonTxnDB

func NonTxnDB(ctx context.Context, id string) DB

NonTxnDB returns a database with given ID or nil if not registered.

func TxnDB

func TxnDB(ctx context.Context) (db DB)

TxnDB returns a Database that matches the context or nil.

The process has a list of database engines registered via Register. Given a context, TxnDB examines if it carries a transaction with any of the registered DBs.

Panics if more than one database matches the context.

type Impl

type Impl struct {
	// Kind identifies this particular DB implementation.
	//
	// Must match Kind() of the produced DB instance.
	Kind string

	// Module is name of the server module with DB implementation, if any.
	Module module.Name

	// ProbeForTxn "probes" a context for an active transaction, returning a DB
	// that can be used to transactionally submit reminders or nil if this is not
	// a transactional context.
	ProbeForTxn func(context.Context) DB

	// NonTxn returns an instance of DB that can be used outside of
	// transactions.
	//
	// This is used by the sweeper to enumerate reminders.
	NonTxn func(context.Context) DB
}

Impl knows how to instantiate DB instances.

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