Documentation
¶
Overview ¶
Package datastore contains a Google Cloud Datastore client.
This package is experimental and may make backwards-incompatible changes.
Example (Auth) ¶
TODO(djd): reevaluate this example given new Client config.
// Initialize an authorized context with Google Developers Console // JSON key. Read the google package examples to learn more about // different authorization flows you can use. // http://godoc.org/github.com/tetrafolium/oauth2/google jsonKey, err := ioutil.ReadFile("/path/to/json/keyfile.json") if err != nil { log.Fatal(err) } conf, err := google.JWTConfigFromJSON( jsonKey, datastore.ScopeDatastore, datastore.ScopeUserEmail, ) if err != nil { log.Fatal(err) } ctx := context.Background() client, err := datastore.NewClient(ctx, "project-id", cloud.WithTokenSource(conf.TokenSource(ctx))) if err != nil { log.Fatal(err) } // Use the client (see other examples). return client
Output:
Example (BasicEntity) ¶
package main import ( "time" ) func main() { // [START basic_entity] type Task struct { Type string Done bool Priority float64 Description string `datastore:",noindex"` PercentComplete float64 Created time.Time } task := &Task{ Type: "Personal", Done: false, Priority: 4, Description: "Learn Cloud Datastore", PercentComplete: 10.0, Created: time.Now(), } // [END basic_entity] _ = task // Use the task in a datastore Put operation. }
Output:
Example (ExplodingProperties) ¶
package main import ( "time" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { // [START exploding_properties] task := &Task{ Tags: []string{"fun", "programming", "learn"}, Collaborators: []string{"alice", "bob", "charlie"}, Created: time.Now(), } // [END exploding_properties] _ = task // Use the task in a datastore Put operation. }
Output:
Example (MetadataKinds) ¶
package main import ( "log" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START kind_run_query] query := datastore.NewQuery("__kind__").KeysOnly() keys, err := client.GetAll(ctx, query, nil) if err != nil { log.Fatalf("client.GetAll: %v", err) } kinds := make([]string, 0, len(keys)) for _, k := range keys { kinds = append(kinds, k.Name()) } // [END kind_run_query] }
Output:
Example (MetadataNamespaces) ¶
package main import ( "log" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START namespace_run_query] const ( startNamespace = "g" endNamespace = "h" ) query := datastore.NewQuery("__namespace__"). Filter("__key__ >=", startNamespace). Filter("__key__ <", endNamespace). KeysOnly() keys, err := client.GetAll(ctx, query, nil) if err != nil { log.Fatalf("client.GetAll: %v", err) } namespaces := make([]string, 0, len(keys)) for _, k := range keys { namespaces = append(namespaces, k.Name()) } // [END namespace_run_query] }
Output:
Example (MetadataProperties) ¶
package main import ( "log" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START property_run_query] query := datastore.NewQuery("__property__").KeysOnly() keys, err := client.GetAll(ctx, query, nil) if err != nil { log.Fatalf("client.GetAll: %v", err) } props := make(map[string][]string) // Map from kind to slice of properties. for _, k := range keys { prop := k.Name() kind := k.Parent().Name() props[kind] = append(props[kind], prop) } // [END property_run_query] }
Output:
Example (MetadataPropertiesForKind) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START property_by_kind_run_query] kindKey := datastore.NewKey(ctx, "__kind__", "Task", 0, nil) query := datastore.NewQuery("__property__").Ancestor(kindKey) type Prop struct { Repr []string `datastore:"property_representation"` } var props []Prop keys, err := client.GetAll(ctx, query, &props) // [END property_by_kind_run_query] _ = err // Check error. _ = keys // Use keys to find property names, and props for their representations. }
Output:
Example (Properties) ¶
package main import ( "time" ) func main() { // [START properties] type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time } task := &Task{ Type: "Personal", Done: false, Priority: 4, Description: "Learn Cloud Datastore", PercentComplete: 10.0, Created: time.Now(), } // [END properties] _ = task // Use the task in a datastore Put operation. }
Output:
Example (SliceProperties) ¶
package main import () func main() { // [START array_value] type Task struct { Tags []string Collaborators []string } task := &Task{ Tags: []string{"fun", "programming"}, Collaborators: []string{"alice", "bob"}, } // [END array_value] _ = task // Use the task in a datastore Put operation. }
Output:
Index ¶
- Constants
- Variables
- func LoadStruct(dst interface{}, p []Property) error
- func WithNamespace(parent context.Context, namespace string) context.Context
- type Client
- func (c *Client) AllocateIDs(ctx context.Context, keys []*Key) ([]*Key, error)
- func (c *Client) Count(ctx context.Context, q *Query) (int, error)
- func (c *Client) Delete(ctx context.Context, key *Key) error
- func (c *Client) DeleteMulti(ctx context.Context, keys []*Key) error
- func (c *Client) Get(ctx context.Context, key *Key, dst interface{}) error
- func (c *Client) GetAll(ctx context.Context, q *Query, dst interface{}) ([]*Key, error)
- func (c *Client) GetMulti(ctx context.Context, keys []*Key, dst interface{}) error
- func (c *Client) NewTransaction(ctx context.Context, opts ...TransactionOption) (*Transaction, error)
- func (c *Client) Put(ctx context.Context, key *Key, src interface{}) (*Key, error)
- func (c *Client) PutMulti(ctx context.Context, keys []*Key, src interface{}) ([]*Key, error)
- func (c *Client) Run(ctx context.Context, q *Query) *Iterator
- func (c *Client) RunInTransaction(ctx context.Context, f func(tx *Transaction) error, opts ...TransactionOption) (*Commit, error)
- type Commit
- type Cursor
- type ErrFieldMismatch
- type Iterator
- type Key
- func (k *Key) Encode() string
- func (k *Key) Equal(o *Key) bool
- func (k *Key) GobDecode(buf []byte) error
- func (k *Key) GobEncode() ([]byte, error)
- func (k *Key) ID() int64
- func (k *Key) Incomplete() bool
- func (k *Key) Kind() string
- func (k *Key) MarshalJSON() ([]byte, error)
- func (k *Key) Name() string
- func (k *Key) Namespace() string
- func (k *Key) Parent() *Key
- func (k *Key) SetParent(v *Key)
- func (k *Key) String() string
- func (k *Key) UnmarshalJSON(buf []byte) error
- type MultiError
- type PendingKey
- type Property
- type PropertyList
- type PropertyLoadSaver
- type Query
- func (q *Query) Ancestor(ancestor *Key) *Query
- func (q *Query) Distinct() *Query
- func (q *Query) End(c Cursor) *Query
- func (q *Query) EventualConsistency() *Query
- func (q *Query) Filter(filterStr string, value interface{}) *Query
- func (q *Query) KeysOnly() *Query
- func (q *Query) Limit(limit int) *Query
- func (q *Query) Offset(offset int) *Query
- func (q *Query) Order(fieldName string) *Query
- func (q *Query) Project(fieldNames ...string) *Query
- func (q *Query) Start(c Cursor) *Query
- func (q *Query) Transaction(t *Transaction) *Query
- type Transaction
- func (t *Transaction) Commit() (*Commit, error)
- func (t *Transaction) Delete(key *Key) error
- func (t *Transaction) DeleteMulti(keys []*Key) error
- func (t *Transaction) Get(key *Key, dst interface{}) error
- func (t *Transaction) GetMulti(keys []*Key, dst interface{}) error
- func (t *Transaction) Put(key *Key, src interface{}) (*PendingKey, error)
- func (t *Transaction) PutMulti(keys []*Key, src interface{}) ([]*PendingKey, error)
- func (t *Transaction) Rollback() error
- type TransactionOption
Examples ¶
- Package (Auth)
- Package (BasicEntity)
- Package (ExplodingProperties)
- Package (MetadataKinds)
- Package (MetadataNamespaces)
- Package (MetadataProperties)
- Package (MetadataPropertiesForKind)
- Package (Properties)
- Package (SliceProperties)
- Client.Delete
- Client.DeleteMulti
- Client.Get
- Client.GetMulti
- Client.Put
- Client.Put (Upsert)
- Client.PutMulti
- Iterator.Cursor
- NewIncompleteKey
- NewKey
- NewKey (WithMultipleParents)
- NewKey (WithParent)
- Query
- Query (Basic)
- Query (CompositeFilter)
- Query (InequalitySort)
- Query (InvalidInequalitySortA)
- Query (InvalidInequalitySortB)
- Query (KeyFilter)
- Query (Kindless)
- Query (PropertyFilter)
- Query (SortAscending)
- Query (SortDescending)
- Query (SortMulti)
- Query (Unindexed)
- Query.Ancestor
- Query.Distinct
- Query.EventualConsistency
- Query.Filter (ArrayEquality)
- Query.Filter (ArrayInequality)
- Query.Filter (Inequality)
- Query.Filter (InvalidInequality)
- Query.Filter (Mixed)
- Query.KeysOnly
- Query.Limit
- Query.Project
- Transaction
- Transaction (GetOrCreate)
- Transaction (Insert)
- Transaction (RunQuery)
- Transaction (Update)
Constants ¶
const ( // ScopeDatastore grants permissions to view and/or manage datastore entities ScopeDatastore = "https://www.googleapis.com/auth/datastore" // ScopeUserEmail grants permission to view the user's email address. // It is required to access the datastore. ScopeUserEmail = "https://www.googleapis.com/auth/userinfo.email" )
Variables ¶
var ( // ErrInvalidEntityType is returned when functions like Get or Next are // passed a dst or src argument of invalid type. ErrInvalidEntityType = errors.New("datastore: invalid entity type") // ErrInvalidKey is returned when an invalid key is presented. ErrInvalidKey = errors.New("datastore: invalid key") // ErrNoSuchEntity is returned when no entity was found for a given key. ErrNoSuchEntity = errors.New("datastore: no such entity") )
var Done = errors.New("datastore: query has no more results")
Done is returned when a query iteration has completed.
var ErrConcurrentTransaction = errors.New("datastore: concurrent transaction")
ErrConcurrentTransaction is returned when a transaction is rolled back due to a conflict with a concurrent transaction.
Functions ¶
func LoadStruct ¶
LoadStruct loads the properties from p to dst. dst must be a struct pointer.
Types ¶
type Client ¶
type Client struct {
// contains filtered or unexported fields
}
Client is a client for reading and writing data in a datastore dataset.
func NewClient ¶
NewClient creates a new Client for a given dataset. If the project ID is empty, it is derived from the DATASTORE_DATASET environment variable.
func (*Client) AllocateIDs ¶
AllocateIDs accepts a slice of incomplete keys and returns a slice of complete keys that are guaranteed to be valid in the datastore
func (*Client) Delete ¶
Delete deletes the entity for the given key.
Example ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") key := datastore.NewKey(ctx, "Task", "sampletask", 0, nil) // [START delete] err := client.Delete(ctx, key) // [END delete] _ = err // Make sure you check err. }
Output:
func (*Client) DeleteMulti ¶
DeleteMulti is a batch version of Delete.
Example ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") var taskKeys []*datastore.Key // Populated with incomplete keys. // [START batch_delete] err := client.DeleteMulti(ctx, taskKeys) // [END batch_delete] _ = err // Make sure you check err. }
Output:
func (*Client) Get ¶
Get loads the entity stored for key into dst, which must be a struct pointer or implement PropertyLoadSaver. If there is no such entity for the key, Get returns ErrNoSuchEntity.
The values of dst's unmatched struct fields are not modified, and matching slice-typed fields are not reset before appending to them. In particular, it is recommended to pass a pointer to a zero valued struct on each Get call.
ErrFieldMismatch is returned when a field is to be loaded into a different type than the one it was stored from, or when a field is missing or unexported in the destination struct. ErrFieldMismatch is only returned if dst is a struct pointer.
Example ¶
package main import ( "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") taskKey := datastore.NewKey(ctx, "Task", "sampleTask", 0, nil) // [START lookup] var task Task err := client.Get(ctx, taskKey, &task) // [END lookup] _ = err // Make sure you check err. }
Output:
func (*Client) GetAll ¶
GetAll runs the provided query in the given context and returns all keys that match that query, as well as appending the values to dst.
dst must have type *[]S or *[]*S or *[]P, for some struct type S or some non- interface, non-pointer type P such that P or *P implements PropertyLoadSaver.
As a special case, *PropertyList is an invalid type for dst, even though a PropertyList is a slice of structs. It is treated as invalid to avoid being mistakenly passed when *[]PropertyList was intended.
The keys returned by GetAll will be in a 1-1 correspondence with the entities added to dst.
If q is a “keys-only” query, GetAll ignores dst and only returns the keys.
func (*Client) GetMulti ¶
GetMulti is a batch version of Get.
dst must be a []S, []*S, []I or []P, for some struct type S, some interface type I, or some non-interface non-pointer type P such that P or *P implements PropertyLoadSaver. If an []I, each element must be a valid dst for Get: it must be a struct pointer or implement PropertyLoadSaver.
As a special case, PropertyList is an invalid type for dst, even though a PropertyList is a slice of structs. It is treated as invalid to avoid being mistakenly passed when []PropertyList was intended.
Example ¶
package main import ( "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") var taskKeys []*datastore.Key // Populated with incomplete keys. // [START batch_lookup] var tasks []*Task err := client.GetMulti(ctx, taskKeys, &tasks) // [END batch_lookup] _ = err // Make sure you check err. }
Output:
func (*Client) NewTransaction ¶
func (c *Client) NewTransaction(ctx context.Context, opts ...TransactionOption) (*Transaction, error)
NewTransaction starts a new transaction.
func (*Client) Put ¶
Put saves the entity src into the datastore with key k. src must be a struct pointer or implement PropertyLoadSaver; if a struct pointer then any unexported fields of that struct will be skipped. If k is an incomplete key, the returned key will be a unique key generated by the datastore.
Example ¶
package main import ( "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START entity_with_parent] parentKey := datastore.NewKey(ctx, "TaskList", "default", 0, nil) key := datastore.NewIncompleteKey(ctx, "Task", parentKey) task := Task{ Type: "Personal", Done: false, Priority: 4, Description: "Learn Cloud Datastore", } // A complete key is assigned to the entity when it is Put. var err error key, err = client.Put(ctx, key, &task) // [END entity_with_parent] _ = err // Make sure you check err. }
Output:
Example (Upsert) ¶
package main import ( "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") task := &Task{} // Populated with appropriate data. key := datastore.NewIncompleteKey(ctx, "Task", nil) // [START upsert] key, err := client.Put(ctx, key, task) // [END upsert] _ = err // Make sure you check err. _ = key // key is the complete key for the newly stored task }
Output:
func (*Client) PutMulti ¶
PutMulti is a batch version of Put.
src must satisfy the same conditions as the dst argument to GetMulti.
Example ¶
package main import ( "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START batch_upsert] tasks := []*Task{ { Type: "Personal", Done: false, Priority: 4, Description: "Learn Cloud Datastore", }, { Type: "Personal", Done: false, Priority: 5, Description: "Integrate Cloud Datastore", }, } keys := []*datastore.Key{ datastore.NewIncompleteKey(ctx, "Task", nil), datastore.NewIncompleteKey(ctx, "Task", nil), } keys, err := client.PutMulti(ctx, keys, tasks) // [END batch_upsert] _ = err // Make sure you check err. _ = keys // keys now has the complete keys for the newly stored tasks. }
Output:
func (*Client) RunInTransaction ¶
func (c *Client) RunInTransaction(ctx context.Context, f func(tx *Transaction) error, opts ...TransactionOption) (*Commit, error)
RunInTransaction runs f in a transaction. f is invoked with a Transaction that f should use for all the transaction's datastore operations.
f must not call Commit or Rollback on the provided Transaction.
If f returns nil, RunInTransaction commits the transaction, returning the Commit and a nil error if it succeeds. If the commit fails due to a conflicting transaction, RunInTransaction retries f with a new Transaction. It gives up and returns ErrConcurrentTransaction after three failed attempts.
If f returns non-nil, then the transaction will be rolled back and RunInTransaction will return the same error. The function f is not retried.
Note that when f returns, the transaction is not committed. Calling code must not assume that any of f's changes have been committed until RunInTransaction returns nil.
Since f may be called multiple times, f should usually be idempotent. Note that Transaction.Get is not idempotent when unmarshaling slice fields.
type Commit ¶
type Commit struct{}
Commit represents the result of a committed transaction.
func (*Commit) Key ¶
func (c *Commit) Key(p *PendingKey) *Key
Key resolves a pending key handle into a final key.
type Cursor ¶
type Cursor struct {
// contains filtered or unexported fields
}
Cursor is an iterator's position. It can be converted to and from an opaque string. A cursor can be used from different HTTP requests, but only with a query with the same kind, ancestor, filter and order constraints.
func DecodeCursor ¶
Decode decodes a cursor from its base-64 string representation.
type ErrFieldMismatch ¶
ErrFieldMismatch is returned when a field is to be loaded into a different type than the one it was stored from, or when a field is missing or unexported in the destination struct. StructType is the type of the struct pointed to by the destination argument passed to Get or to Iterator.Next.
func (*ErrFieldMismatch) Error ¶
func (e *ErrFieldMismatch) Error() string
type Iterator ¶
type Iterator struct {
// contains filtered or unexported fields
}
Iterator is the result of running a query.
func (*Iterator) Cursor ¶
Cursor returns a cursor for the iterator's current location.
Example ¶
package main import ( "log" "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") cursorStr := "" // [START cursor_paging] const pageSize = 5 query := datastore.NewQuery("Tasks").Limit(pageSize) if cursorStr != "" { cursor, err := datastore.DecodeCursor(cursorStr) if err != nil { log.Fatalf("Bad cursor %q: %v", cursorStr, err) } query = query.Start(cursor) } // Read the tasks. var tasks []Task var task Task it := client.Run(ctx, query) _, err := it.Next(&task) for err == nil { tasks = append(tasks, task) _, err = it.Next(&task) } if err != datastore.Done { log.Fatalf("Failed fetching results: %v", err) } // Get the cursor for the next page of results. nextCursor, err := it.Cursor() // [END cursor_paging] _ = err // Check the error. _ = nextCursor // Use nextCursor.String as the next page's token. }
Output:
func (*Iterator) Next ¶
Next returns the key of the next result. When there are no more results, Done is returned as the error.
If the query is not keys only and dst is non-nil, it also loads the entity stored for that key into the struct pointer or PropertyLoadSaver dst, with the same semantics and possible errors as for the Get function.
type Key ¶
type Key struct {
// contains filtered or unexported fields
}
Key represents the datastore key for a stored entity, and is immutable.
func NewIncompleteKey ¶
NewIncompleteKey creates a new incomplete key. kind cannot be empty.
Example ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() // [START incomplete_key] taskKey := datastore.NewIncompleteKey(ctx, "Task", nil) // [END incomplete_key] _ = taskKey // Use the task key for datastore operations. }
Output:
func NewKey ¶
NewKey creates a new key. kind cannot be empty. Either one or both of name and id must be zero. If both are zero, the key returned is incomplete. parent must either be a complete key or nil.
Example ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() // [START named_key] taskKey := datastore.NewKey(ctx, "Task", "sampletask", 0, nil) // [END named_key] _ = taskKey // Use the task key for datastore operations. }
Output:
Example (WithMultipleParents) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() // [START key_with_multilevel_parent] userKey := datastore.NewKey(ctx, "User", "alice", 0, nil) parentKey := datastore.NewKey(ctx, "TaskList", "default", 0, userKey) taskKey := datastore.NewKey(ctx, "Task", "sampleTask", 0, parentKey) // [END key_with_multilevel_parent] _ = taskKey // Use the task key for datastore operations. }
Output:
Example (WithParent) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() // [START key_with_parent] parentKey := datastore.NewKey(ctx, "TaskList", "default", 0, nil) taskKey := datastore.NewKey(ctx, "Task", "sampleTask", 0, parentKey) // [END key_with_parent] _ = taskKey // Use the task key for datastore operations. }
Output:
func (*Key) Encode ¶
Encode returns an opaque representation of the key suitable for use in HTML and URLs. This is compatible with the Python and Java runtimes.
func (*Key) Incomplete ¶
Complete returns whether the key does not refer to a stored entity.
func (*Key) MarshalJSON ¶
func (*Key) UnmarshalJSON ¶
type MultiError ¶
type MultiError []error
MultiError is returned by batch operations when there are errors with particular elements. Errors will be in a one-to-one correspondence with the input elements; successful elements will have a nil entry.
func (MultiError) Error ¶
func (m MultiError) Error() string
type PendingKey ¶
type PendingKey struct {
// contains filtered or unexported fields
}
PendingKey represents the key for newly-inserted entity. It can be resolved into a Key by calling the Key method of Commit.
type Property ¶
type Property struct { // Name is the property name. Name string // Value is the property value. The valid types are: // - int64 // - bool // - string // - float64 // - *Key // - time.Time // - []byte (up to 1 megabyte in length) // This set is smaller than the set of valid struct field types that the // datastore can load and save. A Property Value cannot be a slice (apart // from []byte); use multiple Properties instead. Also, a Value's type // must be explicitly on the list above; it is not sufficient for the // underlying type to be on that list. For example, a Value of "type // myInt64 int64" is invalid. Smaller-width integers and floats are also // invalid. Again, this is more restrictive than the set of valid struct // field types. // // A Value will have an opaque type when loading entities from an index, // such as via a projection query. Load entities into a struct instead // of a PropertyLoadSaver when using a projection query. // // A Value may also be the nil interface value; this is equivalent to // Python's None but not directly representable by a Go struct. Loading // a nil-valued property into a struct will set that field to the zero // value. Value interface{} // NoIndex is whether the datastore cannot index this property. // If NoIndex is set to false, []byte values are limited to 1500 bytes and // string values are limited to 1500 bytes. NoIndex bool // Multiple is whether the entity can have multiple properties with // the same name. Even if a particular instance only has one property with // a certain name, Multiple should be true if a struct would best represent // it as a field of type []T instead of type T. Multiple bool }
Property is a name/value pair plus some metadata. A datastore entity's contents are loaded and saved as a sequence of Properties. An entity can have multiple Properties with the same name, provided that p.Multiple is true on all of that entity's Properties with that name.
func SaveStruct ¶
SaveStruct returns the properties from src as a slice of Properties. src must be a struct pointer.
type PropertyList ¶
type PropertyList []Property
PropertyList converts a []Property to implement PropertyLoadSaver.
func (*PropertyList) Load ¶
func (l *PropertyList) Load(p []Property) error
Load loads all of the provided properties into l. It does not first reset *l to an empty slice.
func (*PropertyList) Save ¶
func (l *PropertyList) Save() ([]Property, error)
Save saves all of l's properties as a slice of Properties.
type PropertyLoadSaver ¶
PropertyLoadSaver can be converted from and to a slice of Properties.
type Query ¶
type Query struct {
// contains filtered or unexported fields
}
Query represents a datastore query.
Example ¶
package main import ( "log" "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() client, err := datastore.NewClient(ctx, "project-id") if err != nil { log.Fatal(err) } // Count the number of the post entities. q := datastore.NewQuery("Post") n, err := client.Count(ctx, q) if err != nil { log.Fatal(err) } log.Println("There are %d posts.", n) // List the posts published since yesterday. yesterday := time.Now().Add(-24 * time.Hour) q = datastore.NewQuery("Post").Filter("PublishedAt >", yesterday) it := client.Run(ctx, q) // Use the iterator. _ = it // Order the posts by the number of comments they have recieved. datastore.NewQuery("Post").Order("-Comments") // Start listing from an offset and limit the results. datastore.NewQuery("Post").Offset(20).Limit(10) }
Output:
Example (Basic) ¶
package main import ( "fmt" "log" "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START basic_query] query := datastore.NewQuery("Task"). Filter("Done =", false). Filter("Priority >=", 4). Order("-Priority") // [END basic_query] // [START run_query] it := client.Run(ctx, query) for { var task Task _, err := it.Next(&task) if err == datastore.Done { break } if err != nil { log.Fatalf("Error fetching next task: %v", err) } fmt.Printf("Task %q, Priority %d\n", task.Description, task.Priority) } // [END run_query] }
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Example (CompositeFilter) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START composite_filter] query := datastore.NewQuery("Task").Filter("Done =", false).Filter("Priority =", 4) // [END composite_filter] _ = query // Use client.Run or client.GetAll to execute the query. }
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Example (InequalitySort) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START inequality_sort] query := datastore.NewQuery("Task"). Filter("Priority >", 3). Order("Priority"). Order("Created") // [END inequality_sort] _ = query // Use client.Run or client.GetAll to execute the query. }
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Example (InvalidInequalitySortA) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START inequality_sort_invalid_not_same] query := datastore.NewQuery("Task"). Filter("Priority >", 3). Order("Created") // [END inequality_sort_invalid_not_same] _ = query // The query is invalid. }
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Example (InvalidInequalitySortB) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START inequality_sort_invalid_not_first] query := datastore.NewQuery("Task"). Filter("Priority >", 3). Order("Created"). Order("Priority") // [END inequality_sort_invalid_not_first] _ = query // The query is invalid. }
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Example (KeyFilter) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() // [START key_filter] key := datastore.NewKey(ctx, "Task", "someTask", 0, nil) query := datastore.NewQuery("Task").Filter("__key__ >", key) // [END key_filter] _ = query // Use client.Run or client.GetAll to execute the query. }
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Example (Kindless) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { var lastSeenKey *datastore.Key // [START kindless_query] query := datastore.NewQuery("").Filter("__key__ >", lastSeenKey) // [END kindless_query] _ = query // Use client.Run or client.GetAll to execute the query. }
Output:
Example (PropertyFilter) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START property_filter] query := datastore.NewQuery("Task").Filter("Done =", false) // [END property_filter] _ = query // Use client.Run or client.GetAll to execute the query. }
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Example (SortAscending) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START ascending_sort] query := datastore.NewQuery("Task").Order("created") // [END ascending_sort] _ = query // Use client.Run or client.GetAll to execute the query. }
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Example (SortDescending) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START descending_sort] query := datastore.NewQuery("Task").Order("-created") // [END descending_sort] _ = query // Use client.Run or client.GetAll to execute the query. }
Output:
Example (SortMulti) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START multi_sort] query := datastore.NewQuery("Task").Order("-priority").Order("created") // [END multi_sort] _ = query // Use client.Run or client.GetAll to execute the query. }
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Example (Unindexed) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START unindexed_property_query] query := datastore.NewQuery("Tasks").Filter("Description =", "A task description") // [END unindexed_property_query] _ = query // Use client.Run or client.GetAll to execute the query. }
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func NewQuery ¶
NewQuery creates a new Query for a specific entity kind.
An empty kind means to return all entities, including entities created and managed by other App Engine features, and is called a kindless query. Kindless queries cannot include filters or sort orders on property values.
func (*Query) Ancestor ¶
Ancestor returns a derivative query with an ancestor filter. The ancestor should not be nil.
Example ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() // [START ancestor_query] ancestor := datastore.NewKey(ctx, "TaskList", "default", 0, nil) query := datastore.NewQuery("Task").Ancestor(ancestor) // [END ancestor_query] _ = query // Use client.Run or client.GetAll to execute the query. }
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func (*Query) Distinct ¶
Distinct returns a derivative query that yields de-duplicated entities with respect to the set of projected fields. It is only used for projection queries.
Example ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START distinct_query] query := datastore.NewQuery("Task"). Project("Priority", "PercentComplete"). Distinct(). Order("Type").Order("Priority") // [END distinct_query] _ = query // Use client.Run or client.GetAll to execute the query. // [START distinct_on_query] // DISTINCT ON not supported in Go API // [END distinct_on_query] }
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func (*Query) EventualConsistency ¶
EventualConsistency returns a derivative query that returns eventually consistent results. It only has an effect on ancestor queries.
Example ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() // [START eventual_consistent_query] ancestor := datastore.NewKey(ctx, "TaskList", "default", 0, nil) query := datastore.NewQuery("Task").Ancestor(ancestor).EventualConsistency() // [END eventual_consistent_query] _ = query // Use client.Run or client.GetAll to execute the query. }
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func (*Query) Filter ¶
Filter returns a derivative query with a field-based filter. The filterStr argument must be a field name followed by optional space, followed by an operator, one of ">", "<", ">=", "<=", or "=". Fields are compared against the provided value using the operator. Multiple filters are AND'ed together. Field names which contain spaces, quote marks, or operator characters should be passed as quoted Go string literals as returned by strconv.Quote or the fmt package's %q verb.
Example (ArrayEquality) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START array_value_equality] query := datastore.NewQuery("Task"). Filter("Tag =", "fun"). Filter("Tag =", "programming") // [END array_value_equality] _ = query // Use client.Run or client.GetAll to execute the query. }
Output:
Example (ArrayInequality) ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START array_value_inequality_range] query := datastore.NewQuery("Task"). Filter("Tag >", "learn"). Filter("Tag <", "math") // [END array_value_inequality_range] _ = query // Use client.Run or client.GetAll to execute the query. }
Output:
Example (Inequality) ¶
package main import ( "time" "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START inequality_range] query := datastore.NewQuery("Task"). Filter("Created >", time.Date(1990, 1, 1, 0, 0, 0, 0, time.UTC)). Filter("Created <", time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)) // [END inequality_range] _ = query // Use client.Run or client.GetAll to execute the query. }
Output:
Example (InvalidInequality) ¶
package main import ( "time" "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START inequality_invalid] query := datastore.NewQuery("Task"). Filter("Created >", time.Date(1990, 1, 1, 0, 0, 0, 0, time.UTC)). Filter("Priority >", 3) // [END inequality_invalid] _ = query // The query is invalid. }
Output:
Example (Mixed) ¶
package main import ( "time" "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START equal_and_inequality_range] query := datastore.NewQuery("Task"). Filter("Priority =", 4). Filter("Done =", false). Filter("Created >", time.Date(1990, 1, 1, 0, 0, 0, 0, time.UTC)). Filter("Created <", time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)) // [END equal_and_inequality_range] _ = query // Use client.Run or client.GetAll to execute the query. }
Output:
func (*Query) KeysOnly ¶
KeysOnly returns a derivative query that yields only keys, not keys and entities. It cannot be used with projection queries.
Example ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START keys_only_query] query := datastore.NewQuery("Task").KeysOnly() // [END keys_only_query] // [START run_keys_only_query] keys, err := client.GetAll(ctx, query, nil) // [END run_keys_only_query] _ = err // Make sure you check err. _ = keys // Keys contains keys for all stored tasks. }
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func (*Query) Limit ¶
Limit returns a derivative query that has a limit on the number of results returned. A negative value means unlimited.
Example ¶
package main import ( "github.com/tetrafolium/gcloud-golang/datastore" ) func main() { // [START limit] query := datastore.NewQuery("Task").Limit(5) // [END limit] _ = query // Use client.Run or client.GetAll to execute the query. }
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func (*Query) Offset ¶
Offset returns a derivative query that has an offset of how many keys to skip over before returning results. A negative value is invalid.
func (*Query) Order ¶
Order returns a derivative query with a field-based sort order. Orders are applied in the order they are added. The default order is ascending; to sort in descending order prefix the fieldName with a minus sign (-). Field names which contain spaces, quote marks, or the minus sign should be passed as quoted Go string literals as returned by strconv.Quote or the fmt package's %q verb.
func (*Query) Project ¶
Project returns a derivative query that yields only the given fields. It cannot be used with KeysOnly.
Example ¶
package main import ( "log" "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START projection_query] query := datastore.NewQuery("Task").Project("Priority", "PercentComplete") // [END projection_query] // [START run_query_projection] var priorities []int var percents []float64 it := client.Run(ctx, query) for { var task Task if _, err := it.Next(&task); err == datastore.Done { break } else if err != nil { log.Fatal(err) } priorities = append(priorities, task.Priority) percents = append(percents, task.PercentComplete) } // [END run_query_projection] }
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func (*Query) Transaction ¶
func (q *Query) Transaction(t *Transaction) *Query
Transaction returns a derivative query that is associated with the given transaction.
All reads performed as part of the transaction will come from a single consistent snapshot. Furthermore, if the transaction is set to a serializable isolation level, another transaction cannot concurrently modify the data that is read or modified by this transaction.
type Transaction ¶
type Transaction struct {
// contains filtered or unexported fields
}
Transaction represents a set of datastore operations to be committed atomically.
Operations are enqueued by calling the Put and Delete methods on Transaction (or their Multi-equivalents). These operations are only committed when the Commit method is invoked. To ensure consistency, reads must be performed by using Transaction's Get method or by using the Transaction method when building a query.
A Transaction must be committed or rolled back exactly once.
Example ¶
package main import ( "log" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) func main() { ctx := context.Background() client, err := datastore.NewClient(ctx, "project-id") if err != nil { log.Fatal(err) } const retries = 3 // Increment a counter. // See https://cloud.google.com/appengine/articles/sharding_counters for // a more scalable solution. type Counter struct { Count int } key := datastore.NewKey(ctx, "counter", "CounterA", 0, nil) for i := 0; i < retries; i++ { tx, err := client.NewTransaction(ctx) if err != nil { break } var c Counter if err := tx.Get(key, &c); err != nil && err != datastore.ErrNoSuchEntity { break } c.Count++ if _, err := tx.Put(key, &c); err != nil { break } // Attempt to commit the transaction. If there's a conflict, try again. if _, err := tx.Commit(); err != datastore.ErrConcurrentTransaction { break } } }
Output:
Example (GetOrCreate) ¶
package main import ( "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") key := datastore.NewKey(ctx, "Task", "sampletask", 0, nil) // [START transactional_get_or_create] _, err := client.RunInTransaction(ctx, func(tx *datastore.Transaction) error { var task Task if err := tx.Get(key, &task); err != datastore.ErrNoSuchEntity { return err } _, err := tx.Put(key, &Task{ Type: "Personal", Done: false, Priority: 4, Description: "Learn Cloud Datastore", }) return err }) // [END transactional_get_or_create] _ = err // Check error. }
Output:
Example (Insert) ¶
package main import ( "log" "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") task := &Task{} // Populated with appropriate data. taskKey := datastore.NewKey(ctx, "Task", "sampleTask", 0, nil) // [START insert] tx, err := client.NewTransaction(ctx) if err != nil { log.Fatalf("client.NewTransaction: %v", err) } // We first check that there is no entity stored with the given key. if err := tx.Get(taskKey, nil); err != datastore.ErrNoSuchEntity { log.Fatalf("tx.Get returned err %v, want ErrNoSuchEntity", err) } if _, err := tx.Put(taskKey, task); err != nil { log.Fatalf("tx.Put: %v", err) } if _, err := tx.Commit(); err != nil { log.Fatalf("tx.Commit: %v", err) } // [END insert] }
Output:
Example (RunQuery) ¶
package main import ( "log" "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") // [START transactional_single_entity_group_read_only] tx, err := client.NewTransaction(ctx) if err != nil { log.Fatalf("client.NewTransaction: %v", err) } defer tx.Rollback() // Transaction only used for read. ancestor := datastore.NewKey(ctx, "TaskList", "default", 0, nil) query := datastore.NewQuery("Task").Ancestor(ancestor).Transaction(tx) var tasks []Task _, err = client.GetAll(ctx, query, &tasks) // [END transactional_single_entity_group_read_only] _ = err // Check error. }
Output:
Example (Update) ¶
package main import ( "log" "time" "github.com/tetrafolium/gcloud-golang/datastore" "golang.org/x/net/context" ) type Task struct { Type string Done bool Priority int Description string `datastore:",noindex"` PercentComplete float64 Created time.Time Tags []string Collaborators []string } func main() { ctx := context.Background() client, _ := datastore.NewClient(ctx, "my-proj") taskKey := datastore.NewKey(ctx, "Task", "sampleTask", 0, nil) // [START update] tx, err := client.NewTransaction(ctx) if err != nil { log.Fatalf("client.NewTransaction: %v", err) } var task Task if err := tx.Get(taskKey, &task); err != nil { log.Fatalf("tx.Get: %v", err) } task.Priority = 5 if _, err := tx.Put(taskKey, task); err != nil { log.Fatalf("tx.Put: %v", err) } if _, err := tx.Commit(); err != nil { log.Fatalf("tx.Commit: %v", err) } // [END update] }
Output:
func (*Transaction) Commit ¶
func (t *Transaction) Commit() (*Commit, error)
Commit applies the enqueued operations atomically.
func (*Transaction) Delete ¶
func (t *Transaction) Delete(key *Key) error
Delete is the transaction-specific version of the package function Delete. Delete enqueues the deletion of the entity for the given key, to be committed atomically upon calling Commit.
func (*Transaction) DeleteMulti ¶
func (t *Transaction) DeleteMulti(keys []*Key) error
DeleteMulti is a batch version of Delete.
func (*Transaction) Get ¶
func (t *Transaction) Get(key *Key, dst interface{}) error
Get is the transaction-specific version of the package function Get. All reads performed during the transaction will come from a single consistent snapshot. Furthermore, if the transaction is set to a serializable isolation level, another transaction cannot concurrently modify the data that is read or modified by this transaction.
func (*Transaction) GetMulti ¶
func (t *Transaction) GetMulti(keys []*Key, dst interface{}) error
GetMulti is a batch version of Get.
func (*Transaction) Put ¶
func (t *Transaction) Put(key *Key, src interface{}) (*PendingKey, error)
Put is the transaction-specific version of the package function Put.
Put returns a PendingKey which can be resolved into a Key using the return value from a successful Commit. If key is an incomplete key, the returned pending key will resolve to a unique key generated by the datastore.
func (*Transaction) PutMulti ¶
func (t *Transaction) PutMulti(keys []*Key, src interface{}) ([]*PendingKey, error)
PutMulti is a batch version of Put. One PendingKey is returned for each element of src in the same order.
func (*Transaction) Rollback ¶
func (t *Transaction) Rollback() error
Rollback abandons a pending transaction.
type TransactionOption ¶
type TransactionOption interface {
// contains filtered or unexported methods
}
A TransactionOption configures the Transaction returned by NewTransaction.
var ( // Snapshot causes the transaction to enforce a snapshot isolation level. Snapshot TransactionOption = isolation{pb.BeginTransactionRequest_SNAPSHOT} // Serializable causes the transaction to enforce a serializable isolation level. Serializable TransactionOption = isolation{pb.BeginTransactionRequest_SERIALIZABLE} )