Cloud Spanner API - Class Google::Cloud::Spanner::BatchClient (v2.16.0)

Reference documentation and code samples for the Cloud Spanner API class Google::Cloud::Spanner::BatchClient.

BatchClient

Provides a batch client that can be used to read data from a Cloud Spanner database. An instance of this class is tied to a specific database.

BatchClient is useful when one wants to read or query a large amount of data from Cloud Spanner across multiple processes, even across different machines. It allows to create partitions of Cloud Spanner database and then read or query over each partition independently yet at the same snapshot.

See Project#batch_client.

Inherits

  • Object

Example

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

batch_client = spanner.batch_client "my-instance", "my-database"

batch_snapshot = batch_client.batch_snapshot

partitions = batch_snapshot.partition_read "users", [:id, :name]

partition = partitions.first

serialized_snapshot = batch_snapshot.dump
serialized_partition = partition.dump

# In a separate process
new_batch_snapshot = batch_client.load_batch_snapshot \
  serialized_snapshot

new_partition = batch_client.load_partition \
  serialized_partition

results = new_batch_snapshot.execute_partition \
  new_partition

Methods

#batch_snapshot

def batch_snapshot(strong: nil, timestamp: nil, read_timestamp: nil, staleness: nil, exact_staleness: nil) { |snapshot| ... } -> Google::Cloud::Spanner::BatchSnapshot

Returns a BatchSnapshot context in which multiple reads and/or queries can be performed. All reads/queries will use the same timestamp, and the timestamp can be inspected after this transaction is created successfully. This is a blocking method since it waits to finish the RPCs.

Parameters
  • strong (true, false) (defaults to: nil) — Read at a timestamp where all previously committed transactions are visible.
  • timestamp (Time, DateTime) (defaults to: nil) — Executes all reads at the given timestamp. Unlike other modes, reads at a specific timestamp are repeatable; the same read at the same timestamp always returns the same data. If the timestamp is in the future, the read will block until the specified timestamp, modulo the read's deadline.

    Useful for large scale consistent reads such as mapreduces, or for coordinating many reads against a consistent snapshot of the data. (See TransactionOptions.)

  • read_timestamp (Time, DateTime) (defaults to: nil) — Same as timestamp.
  • staleness (Numeric) (defaults to: nil) — Executes all reads at a timestamp that is staleness seconds old. For example, the number 10.1 is translated to 10 seconds and 100 milliseconds.

    Guarantees that all writes that have committed more than the specified number of seconds ago are visible. Because Cloud Spanner chooses the exact timestamp, this mode works even if the client's local clock is substantially skewed from Cloud Spanner commit timestamps.

    Useful for reading at nearby replicas without the distributed timestamp negotiation overhead of single-use staleness. (See TransactionOptions.)

  • exact_staleness (Numeric) (defaults to: nil) — Same as staleness.
Yields
  • (snapshot) — The block for reading and writing data.
Yield Parameter
Returns
Example 
require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

batch_client = spanner.batch_client "my-instance", "my-database"

batch_snapshot = batch_client.batch_snapshot

partitions = batch_snapshot.partition_read "users", [:id, :name]

partition = partitions.first

serialized_snapshot = batch_snapshot.dump
serialized_partition = partition.dump

# In a separate process
new_batch_snapshot = batch_client.load_batch_snapshot \
  serialized_snapshot

new_partition = batch_client.load_partition \
  serialized_partition

results = new_batch_snapshot.execute_partition \
  new_partition

#database

def database() -> Database

The Spanner database connected to.

Returns
  • (Database)

#database_id

def database_id() -> String

The unique identifier for the database.

Returns
  • (String)

#fields

def fields(types) -> Fields

Creates a configuration object (Fields) that may be provided to queries or used to create STRUCT objects. (The STRUCT will be represented by the Data class.) See Client#execute and/or Fields#struct.

For more information, see Data Types - Constructing a STRUCT.

Parameter
  • types (Array, Hash) —

    Accepts an array or hash types.

    Arrays can contain just the type value, or a sub-array of the field's name and type value. Hash keys must contain the field name as a Symbol or String, or the field position as an Integer. Hash values must contain the type value. If a Hash is used the fields will be created using the same order as the Hash keys.

    Supported type values incude:

    • :BOOL
    • :BYTES
    • :DATE
    • :FLOAT64
    • :INT64
    • :STRING
    • :TIMESTAMP
    • Array - Lists are specified by providing the type code in an array. For example, an array of integers are specified as [:INT64].
    • Fields - Nested Structs are specified by providing a Fields object.
Returns
  • (Fields) — The fields of the given types.
Examples

Create a STRUCT value with named fields using Fields object:

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

batch_client = spanner.batch_client "my-instance", "my-database"

named_type = batch_client.fields(
  { id: :INT64, name: :STRING, active: :BOOL }
)
named_data = named_type.struct(
  { id: 42, name: nil, active: false }
)

Create a STRUCT value with anonymous field names:

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

batch_client = spanner.batch_client "my-instance", "my-database"

anon_type = batch_client.fields [:INT64, :STRING, :BOOL]
anon_data = anon_type.struct [42, nil, false]

Create a STRUCT value with duplicate field names:

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

batch_client = spanner.batch_client "my-instance", "my-database"

dup_type = batch_client.fields(
  [[:x, :INT64], [:x, :STRING], [:x, :BOOL]]
)
dup_data = dup_type.struct [42, nil, false]

#instance

def instance() -> Instance

The Spanner instance connected to.

Returns
  • (Instance)

#instance_id

def instance_id() -> String

The unique identifier for the instance.

Returns
  • (String)

#load_batch_snapshot

def load_batch_snapshot(serialized_snapshot) -> Google::Cloud::Spanner::BatchSnapshot

Returns a BatchSnapshot context in which multiple reads and/or queries can be performed. All reads/queries will use the same timestamp, and the timestamp can be inspected after this transaction is created successfully. This method does not perform an RPC.

Parameter
Returns
Example 
require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

batch_client = spanner.batch_client "my-instance", "my-database"

batch_snapshot = batch_client.batch_snapshot

partitions = batch_snapshot.partition_read "users", [:id, :name]

partition = partitions.first

serialized_snapshot = batch_snapshot.dump
serialized_partition = partition.dump

# In a separate process
new_batch_snapshot = batch_client.load_batch_snapshot \
  serialized_snapshot

new_partition = batch_client.load_partition \
  serialized_partition

results = new_batch_snapshot.execute_partition \
  new_partition

#load_partition

def load_partition(serialized_partition) -> Google::Cloud::Spanner::Partition

Returns a Partition from a serialized representation. See Partition.load.

Parameter
  • serialized_partition (String) — The serialized representation of an existing batch partition. See Partition#dump.
Returns
Example 
require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

batch_client = spanner.batch_client "my-instance", "my-database"

batch_snapshot = batch_client.batch_snapshot

partitions = batch_snapshot.partition_read "users", [:id, :name]

partition = partitions.first

serialized_snapshot = batch_snapshot.dump
serialized_partition = partition.dump

# In a separate process
new_batch_snapshot = batch_client.load_batch_snapshot \
  serialized_snapshot

new_partition = batch_client.load_partition \
  serialized_partition

results = new_batch_snapshot.execute_partition \
  new_partition

#project

def project() -> Project

The Spanner project connected to.

Returns

#project_id

def project_id() -> String

The unique identifier for the project.

Returns
  • (String)

#range

def range(beginning, ending, exclude_begin: false, exclude_end: false) -> Google::Cloud::Spanner::Range

Creates a Spanner Range. This can be used in place of a Ruby Range when needing to exclude the beginning value.

Parameters
  • beginning (Object) — The object that defines the beginning of the range.
  • ending (Object) — The object that defines the end of the range.
  • exclude_begin (Boolean) (defaults to: false) — Determines if the range excludes its beginning value. Default is false.
  • exclude_end (Boolean) (defaults to: false) — Determines if the range excludes its ending value. Default is false.
Returns
Example 
require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

batch_client = spanner.batch_client "my-instance", "my-database"
batch_snapshot = batch_client.batch_snapshot

key_range = batch_client.range 1, 100

partitions = batch_snapshot.partition_read "users", [:id, :name],
                                        keys: key_range