Class: Google::Cloud::Spanner::Results

Inherits:
Object
  • Object
show all
Defined in:
lib/google/cloud/spanner/results.rb

Overview

# Results

Represents the result set from an operation returning data.

See Client#execute and Client#read.

Examples:

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

db = spanner.client "my-instance", "my-database"

results = db.execute "SELECT * FROM users"

results.fields.pairs.each do |name, type|
  puts "Column #{name} is type {type}"
end

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.execute(service, session_path, sql, params: nil, types: nil, transaction: nil) ⇒ Object 



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# File 'lib/google/cloud/spanner/results.rb', line 206

def self.execute service, session_path, sql, params: nil, types: nil,
                 transaction: nil
  execute_options = { transaction: transaction, params: params,
                      types: types }
  enum = service.streaming_execute_sql session_path, sql,
                                       execute_options
  from_enum(enum, service).tap do |results|
    results.instance_variable_set :@session_path,    session_path
    results.instance_variable_set :@sql,             sql
    results.instance_variable_set :@execute_options, execute_options
  end
end

.from_enum(enum, service) ⇒ Object 



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# File 'lib/google/cloud/spanner/results.rb', line 195

def self.from_enum enum, service
  grpc = enum.peek
  new.tap do |results|
    results.instance_variable_set :@metadata, grpc.metadata
    results.instance_variable_set :@stats,    grpc.stats
    results.instance_variable_set :@enum,     enum
    results.instance_variable_set :@service,  service
  end
end

.read(service, session_path, table, columns, keys: nil, index: nil, limit: nil, transaction: nil) ⇒ Object 



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# File 'lib/google/cloud/spanner/results.rb', line 220

def self.read service, session_path, table, columns, keys: nil,
              index: nil, limit: nil, transaction: nil
  read_options = { keys: keys, index: index, limit: limit,
                   transaction: transaction }
  enum = service.streaming_read_table \
    session_path, table, columns, read_options
  from_enum(enum, service).tap do |results|
    results.instance_variable_set :@session_path, session_path
    results.instance_variable_set :@table,        table
    results.instance_variable_set :@columns,      columns
    results.instance_variable_set :@read_options, read_options
  end
end

Instance Method Details

#fields ⇒ Fields

Returns the field names and types for the rows in the returned data.

Examples:

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

db = spanner.client "my-instance", "my-database"

results = db.execute "SELECT * FROM users"

results.fields.pairs.each do |name, type|
  puts "Column #{name} is type {type}"
end

Returns:

  • (Fields) —

    The fields of the returned data.



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# File 'lib/google/cloud/spanner/results.rb', line 71

def fields
  @fields ||= Fields.from_grpc @metadata.row_type.fields
end

#inspect ⇒ Object 



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# File 'lib/google/cloud/spanner/results.rb', line 240

def inspect
  "#<#{self.class.name} #{self}>"
end

#rows {|row| ... } ⇒ Object

The values returned from the request.

Examples:

require "google/cloud/spanner"

spanner = Google::Cloud::Spanner.new

db = spanner.client "my-instance", "my-database"

results = db.execute "SELECT * FROM users"

results.rows.each do |row|
  puts "User #{row[:id]} is #{row[:name]}"
end

Yields:

  • (row) —

    An enumerator for the rows.

Yield Parameters:

  • row (Data) —

    object that contains the data values.



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# File 'lib/google/cloud/spanner/results.rb', line 96

def rows
  return nil if @closed

  unless block_given?
    return enum_for(:rows)
  end

  fields = @metadata.row_type.fields
  values = []
  buffered_responses = []
  buffer_upper_bound = 10
  chunked_value = nil
  resume_token = nil

  # Cannot call Enumerator#each because it won't return the first
  # value that was already identified when calling Enumerator#peek.
  # Iterate only using Enumerator#next and break on StopIteration.
  loop do
    begin
      grpc = @enum.next
      # metadata should be set before the first iteration...
      @metadata ||= grpc.metadata
      @stats ||= grpc.stats

      buffered_responses << grpc

      if (grpc.resume_token && grpc.resume_token != "") ||
        buffered_responses.size >= buffer_upper_bound
        # This can set the resume_token to nil
        resume_token = grpc.resume_token

        buffered_responses.each do |resp|
          if chunked_value
            resp.values.unshift merge(chunked_value, resp.values.shift)
            chunked_value = nil
          end
          to_iterate = values + Array(resp.values)
          chunked_value = to_iterate.pop if resp.chunked_value
          values = to_iterate.pop(to_iterate.count % fields.count)
          to_iterate.each_slice(fields.count) do |slice|
            yield Data.from_grpc(slice, fields)
          end
        end

        # Flush the buffered responses now that they are all handled
        buffered_responses = []
      end
    rescue GRPC::Unavailable => err
      if resume_token.nil? || resume_token.empty?
        # Re-raise if the resume_token is not a valid value.
        # This can happen if the buffer was flushed.
        raise Google::Cloud::Error.from_error(err)
      end

      # Resume the stream from the last known resume_token
      if @execute_options
        @enum = @service.streaming_execute_sql \
          @session_path, @sql,
          @execute_options.merge(resume_token: resume_token)
      else
        @enum = @service.streaming_read_table \
          @session_path, @table, @columns,
          @read_options.merge(resume_token: resume_token)
      end

      # Flush the buffered responses to reset to the resume_token
      buffered_responses = []
    rescue GRPC::BadStatus => err
      raise Google::Cloud::Error.from_error(err)
    rescue StopIteration
      break
    end
  end

  # clear out any remaining values left over
  buffered_responses.each do |resp|
    if chunked_value
      resp.values.unshift merge(chunked_value, resp.values.shift)
      chunked_value = nil
    end
    to_iterate = values + Array(resp.values)
    chunked_value = to_iterate.pop if resp.chunked_value
    values = to_iterate.pop(to_iterate.count % fields.count)
    to_iterate.each_slice(fields.count) do |slice|
      yield Data.from_grpc(slice, fields)
    end
  end
  values.each_slice(fields.count) do |slice|
    yield Data.from_grpc(slice, fields)
  end

  # If we get this far then we can release the session
  @closed = true
  nil
end

#timestamp ⇒ Time

The read timestamp chosen for single-use snapshots (read-only transactions).

Returns:

  • (Time) —

    The chosen timestamp.



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# File 'lib/google/cloud/spanner/results.rb', line 48

def timestamp
  return nil if @metadata.nil? || @metadata.transaction.nil?
  Convert.timestamp_to_time @metadata.transaction.read_timestamp
end

#to_s ⇒ Object 



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# File 'lib/google/cloud/spanner/results.rb', line 235

def to_s
  "(#{fields.inspect} streaming)"
end